Buffering ahead nonstop into the cache results in nonstop disk or network
activity to read stream data from wherever it may originate. Currently,
there's no way to configure the demuxer to back off once it's buffered
ahead enough data, since the cache limit will be perpetually not-reached as
a stream continues to play, until the entire stream is eventually buffered.
On a laptop with an i9-12900H with decoding performed by the iGPU,
watching a locally-saved 1080p video which hasn't been buffered into the
page cache consumes approximately 15 W even with caching enabled. When
configuring a hysteresis to make the demuxer back off, power consumption
drops to 9 W when watching the same video, resulting in a whopping 6 W of
power savings.
To make it possible to attain significant power savings via caching, add
a --demuxer-hysteresis-secs option to configure a hysteresis to make the
demuxer back off until there's only the configured number of seconds
remaining in the cache from the current playback position.
This feature is disabled by default.
In the previous change, I replaced the callsites that used
`av_init_packet`, but there are a handful of places that use stack
allocated packets with no initialisation.
In one case, I just switched to heap allocation as it's only done once
per stream at most.
In the other case, I removed our usage of the AVPackets as a
convenience mechanism to transfer data into a heap allocated packet.
Instead, I inlined the data copying.
Now that 0.35 has been released, we can consider increasing our minimum
required ffmpeg version. Currently, we think 4.4 is the most recent
version we can move to (from the current requirement of 4.0).
This allows us to remove a few conditionals. There are more that we
won't be able to remove unless we move further up to 5.1.
This patch adds support for two extra WAVEFORMATEXTENSIBLE GUID tags
that can appear inside RIFF headers. It also adds support for extra
codec IDs that may appear as their own unique wSubFormats inside RIFF
headers, such as ATRAC9 inside matroska, as one example.
Fixes#10757.
This define was always just a stopgap for that two month period (August
2021 - October 2021) where the bytes_read field in ffmpeg was completely
missing. Before that time, it was a private member in a struct (which
mpv used). Afterwards, it officially became public. Fortunately, the
lack of this field never actually made it into a release, so it could
have only possibly affected people building from the master branch.
Since ffmpeg 5.0 came out recently, and it's been plenty of months since
that two month window, we can go ahead and drop this check. This
finishes up the work done in 78cfeee2b9.
Sidenote: the cached ffmpeg version in the mingw ci were from that time
period when the bytes_read field was missing. The N in the workflow is
bumped to force a full rebuild and fresh clone of ffmpeg.
This needs to be forwarded from the AVStream to the AVPacket itself, so
that it reaches the decoder. There exists an FFmpeg function for this,
we just need to call it. (Also add some logging)
The extension is completely arbitrary since ebml_defs.c isn't a real c
file that actually is compiled at any point in time. It's just used as
an include. The reason for changing the extension is because meson needs
to add this to its list of sources for dependency/ordering purposes.
Understandably, meson will try to compile any .c file added to a c
project executable object. Obviously, this compilation will never
succeed, and this shouldn't be compiled anyways. Just make it .inc
instead.
This seems to work on gcc, clang and mingw as-is, but I made it
conditional on __GNUC__ just in case, even though I can't figure out
which compilers we care about that don't export this define.
Also replace all instances of assert(0) in the code by MP_UNREACHABLE(),
which is a strict improvement.
The bytes_read struct member in AVIOContext is now officially public,
so its usage no longer has to be specified as non-compliance with
FFmpeg's ABI/API rules.
That said, unfortunately there was a short period of time between
August 2021 and October 2021 where the struct member did not exist
in FFmpeg's git master, so keep a feature check for it alive for
now to enable building with those versions. Thankfully, no release
version of FFmpeg will be without this field, so it should be
possible to drop this check with time.
Finally, simplify the function in case the struct member is not
found. After all, there is zero reason to iterate through the AVIO
contexts if we cannot get the information we require.
This exposes whether a video track is detected as an image, which is
useful for profile conditions, property expansion and lavfi-complex.
The lavf demuxer sets image to true when the existing check detects an
image.
When the lavf demuxer fails, the mf one guesses if the file is an image
by its extension, so sh->image is set to true when the mf demuxer
succeds and there's only one file.
The mkv demuxer just sets image to true for any attached picture.
The timeline demuxer just copies the value of image from source to
destination. This sets image to true for attached pictures, standalone
images and images added with !new_stream in EDL playlists, but it is
imperfect since you could concatenate multiple images in an EDL playlist
(which should be done with the mf demuxer anyway). This is good enough
anyway since the comment of the modified function already says it is
"Imperfect and arbitrary".
This moves the image check to where the number of frames is available of
comparison, which allows not detecting jpg and png videos as images, and
detecting 1-frame gifs as images. This works with the mjpeg and png
videos in the FATE suite, though unfortunately the bmp video is still
detected as an image since it has nb_frames = 0.
aliaspix streams are also now considered images.
Attached pictures are now treated like standalone images, so audio with
attached pictures now has mf-fps as container-fps instead of
unavailable, which makes it consistent with external cover art, which
was already being assigned mf-fps.
Unfortunately images in a codec commonly used for videos are never
detected, and detection was inaccurate even using the now private
codec_info_nb_frames field in AVStream, and mediainfo gets them wrong
too, so I guess it's just a lost cause.
Unfortunately, this functionality in large part based on a struct
member that was made private in FFmpeg/FFmpeg@7489f63281
in May. Unfortunately, this was not noticed during review.
This reverts commit 0862664ac9.
This exposes whether a video track is detected as an image. This is
useful for profile conditions, property expansion and lavfi-complex, and
is more accurate than any detection even Lua scripts can perform, since
they can't differentiate between images and videos without container-fps
and audio and with duration 1 (which is the duration set by the mf
demuxer with the default --mf-fps=1).
The lavf demuxer image check is moved to where the number of frames is
available for comparison, and is modified to check the number of frames
and duration instead of the video codec. This doesn't misdetect videos
in a codec commonly used for images (e.g. mjpeg) as images, and can
detect images in a codec commonly used for videos (e.g. 1-frame gifs).
pix files are also now detected as images, while before they weren't
since the condition was checking if the AVInputFormat name ends with
_pipe, and alias_pix doesn't.
Both nb_frames and codec_info_nb_frames are checked because nb_frames is
0 for some video codecs (hevc, av1, vc1, mpeg1video, vp9 if forcing
--demuxer=lavf), and codec_info_nb_frames is 1 for others (mpeg, mpeg4,
wmv3).
The duration is checked as well because for some uncommon codecs and
containers found in FFMpeg's FATE suite, libavformat returns nb_frames =
0 and codec_info_nb_frames = 1. For some of them it even returns
duration = 0, so they are blacklisted in order to never be considered
images.
The extra codecs that would have to be blacklisted without checking the
duration are AV_CODEC_ID_4XM, AV_CODEC_ID_BINKVIDEO,
AV_CODEC_ID_DSICINVIDEO, AV_CODEC_ID_ESCAPE130, AV_CODEC_ID_MMVIDEO,
AV_CODEC_ID_NUV, AV_CODEC_ID_RL2, AV_CODEC_ID_SMACKVIDEO and
AV_CODEC_ID_XAN_WC3, while the containers are film-cpk, ivf and ogg.
The lower limit for duration is 10 because that's the duration of
1-frame gifs.
Streams with codec_info_nb_frames 0 are not considered images because
vp9 and av1 have nb_frames = 0 and codec_info_nb_frames = 0, and we
can't rely on just the duration to detect them because they could be
livestreams without an initial duration, and actually even if we could
for these codecs libavformat returns huge negative durations like
-9223372036854775808.
Some more images in the FATE suite that are really frames cut from a
video in an uncommon codec and container, like cine/bayer_gbrg8.cine,
could be detected by allowing codec_info_nb_frames = 0, but then any
present and future video codec with nb_frames = 0 and
codec_info_nb_frames = 0 would need to be added to the blacklist. Some
even have duration > 10, so to detect these images the duration check
would have to be removed, and all the previously mentioned extra codecs
and containers would have to be added added to the blacklists, which
means that images that use them (if they exist anywhere) will never be
detected. These FATE images aren't detected as such by mediainfo either
anyway, nor can a Lua script reliably detect them as images since they
have container-fps and duration > 0 and != 1, and you probably will
never see files like them anywhere else.
For attached pictures the lavf demuxer always set image to true, which
is necessary because they have duration > 10. There is a minor change in
behavior for which audio with attached pictures now has mf-fps as
container-fps instead of unavailable, but this makes it consistent with
external cover art, which was already being assigned mf-fps.
When the lavf demuxer fails, the mf one guesses if the file is an image
by its extension, so sh->image is set to true when the mf demuxer
succeds and there's only one file.
Even if you add a video's file type to --mf-type and open it with the mf
protocol, only the first frame is used, so setting image to true is
still accurate.
When converting an image to the extensions listed in demux/demux_mf.c,
tga and pam files are currently the only ones detected by the mf demuxer
rather than lavf. Actually they are detected with the image2 format, but
it is blacklisted; see d0fee0ac33.
The mkv demuxer just sets image to true for any attached picture.
The timeline demuxer just copies the value of image from source to
destination. This sets image to true for attached pictures, standalone
images and images added with !new_stream in EDL playlists, but it is
imperfect since you could concatenate multiple images in an EDL playlist
(which should be done with the mf demuxer anyway). This is good enough
anyway since the comment of the modified function already says it is
"Imperfect and arbitrary".
Without this, cases where the parser cannot return data right away
will end up utilizing the following fed packet's timestamps. This
will in turn cause an unnecessary offset in the audio stream
timestamps.
An example of such buffered parser in libavcodec is the EAC3 one.
Last time it was extended was de3ecc60 from 8K to 512K two years ago.
The issue currently is that youtube EDL files can get very big.
Size of about 520K (one line), was observed, at the time of writing:
mpv https://youtube.com/watch?v=DBzFQgSMHdQ --ytdl-format=299
ytdl_hook.lua is unaffected by this because EDL lists don't go through
the file reader at demux_playlist.c (where each line was limited to
512K before this commit), however, EDL files on disk which are
loaded with --playlist=file.edl do.
Increase the limit to 2M so that such EDL files can also be loaded
from disk.
Fixes#9186
in->byte_level_seeks field is written and modified inside
update_bytes_read at the same time when demux_get_reader_state
is executing, which locks the demux thread mutex. This results
in a data race, reported by Thread Sanitizer when playing mp3 file
of sufficient long length.
Though, only when the output format is matroska, to avoid muxing errors.
This is quite useful when the input has ASS subtitles, as they tend to
rely on embedded fonts.
dump_cache() calls qsort() to order an array of pointers, while the
comparator forgets it's receiving pointers to pointers.
Since cache-dumping over multiple cache ranges is fairly rare, this
seems to have gone unnoticed.
Add new header which shows up as tags/metadata (associated with
--display-tags). The way this is added means it doesn't always work,
because root->meta (see code) can be NULL for some absurd reason. But it
works for the one case I intended to use it (ytdl_hook, see next
commit), though only in default configurations.
Before this commit, the user could specify a printf format string
which wasn't verified, and could result in:
- Undefined behavior due to missing or non-matching arguments.
- Buffer overflow due to untested result length.
The offending code was added at commit 103a9609 (2002, mplayer svn):
git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@4566 b3059339-0415-0410-9bf9-f77b7e298cf2
It moved around but was not modified meaningfully until now.
Now we reject all conversion specifiers at the format except %%
and a simple subset of the valid specifiers. Also, we now use
snprintf to avoid buffer overflow.
The format string is provided by the user as part of mf:// URI.
Report and initial patch by Stefan Schiller.
Patch reviewed by @jeeb, @sfan5, Stefan Schiller.
This reverts commit 41243e7c4f.
This fixes image format detection. FFmpeg has an utter called "image2",
which is designed to read patterns in filenames (so you can play
something like "%*.jpg" for all jpg files in the current directory).
"image2" is not what we want; it's just broken with custom I/O like
mpv uses it, and we don't want to "accidentally" interpret filenames
as pattern. That's why mpv blacklists it.
Unfortunately, "image2" is sometimes the format that FFmpeg's probe API
returns as best match. Thus demux_lavf fails to detect the file type,
and after some more futile attempts, we end up at demux_mf, which uses
detection by file extension. (Not sure why. I guess MPlayer did that,
and foudn that sufficient.) If the file extension is wrong (which
happens a lot because apparently the world is full of idiots who don't
manage to get the most simple things right), the image "loads", but
decoding obviously fails.
There's no easy way around this. The FFmpeg API has no mechanism to
exclude a specific format from probing (like image2, which breaks stuff
for us). Out of the 5 probe functions the API provides, none can probe
a specific format or include or exclude specific formats. The main
problem is that AVInputFormat.read_probe is a private symbol.
FFmpeg itself has no problem opening such files. It turns out that it
works, because even though image2 by itself uses detection by file
extension, it uses private API to further probe the exact format. It
explicitly excludes itself to prevent recursion.
But fortunately, that also means that it's impossible to get the image2
format if no filename is passed to the prober. (No filename, no file
extension.) Apparently we pass it in because it helps in corner cases.
Until almost 3 years ago, we passed the filename only when normal
probing already failed. Restore this by this revert. It makes
incorrectly named files work. The revert also makes the (apparently
forgotten) comment above the touched line of code true again.
Yes, quite possible that this breaks some mp3s again. You can't win
with FFmpeg. Thanks FFmpeg for making us fail at opening simple image
files and/or the most widely used file format for audio.
Well, whatever. Only results in an error message being printed, because
there is no other error reporting mechanism, and the general policy is
to keep trying with the rest of the data (i.e. not report EOF).
Such files violate the specification. Unfortunately, I could not test
whether it really works correctly, since I don't have a sample at hand
that is not broken in this regard.
The header probing hacks were previously all broken. They only worked
the first time the archive file was open. Since subsequent opens (on
seek) occured in the middle of the source stream rather than at the
beginning, the stream_read_peek calls meant to retrieve the headers were
instead returning random bytes in the middle of the file.
Perhaps the worst manifestation of this was when seeking within a
multi-volume .rar archive with the "legacy" file naming pattern. If the
seek required a reopen, the fact that the archive was multi-volume would
be forgotten and the file would appear truncated terminating playback.
To solve this, only perform the header probling the first time the
archive is opened. Save the results and reuse them on subsequent
reopens. Put this in a wrapper so this is transparent to
demux_libarchive.
Instead of just picking the last tag that was encountered. The order of
the tags still depends on the file order.
This is probably wrong, and we should respect TargetTypeValue. But
despite staring at the spec, I have no idea what the hell this should
do, so fuck that.
Fixes: #7604
Unfortunately, attached pictures (from tags etc.) are treated as video
tracks. That meant --sub-create-cc-track added a CC track for them as
well. Stop doing that.
See: #7608
Replace use of .min==1 with a proper flag. This is a good idea, because
it has nothing to do with numeric limits (also see commit 9d32d62b61
for how this can go wrong).
With this, m_option.min/max are strictly used for numeric limits.
Add an infrastructure for collecting performance-related data, use it in
some places. Add rendering of them to stats.lua.
There were two main goals: minimal impact on the normal code and normal
playback. So all these stats_* function calls either happen only during
initialization, or return immediately if no stats collection is going
on. That's why it does this lazily adding of stats entries etc. (a first
iteration made each stats entry an API thing, instead of just a single
stats_ctx, but I thought that was getting too intrusive in the "normal"
code, even if everything gets worse inside of stats.c).
You could get most of this information from various profilers (including
the extremely primitive --dump-stats thing in mpv), but this makes it
easier to see the most important information at once (at least in
theory), partially because we know best about the context of various
things.
Not very happy with this. It's all pretty primitive and dumb. At this
point I just wanted to get over with it, without necessarily having to
revisit it later, but with having my stupid statistics.
Somehow the code feels terrible. There are a lot of meh decisions in
there that could be better or worse (but mostly could be better), and it
just sucks but it's also trivial and uninteresting and does the job. I
guess I hate programming. It's so tedious and the result is always shit.
Anyway, enjoy.
As an unfortunate disaster, min/max values use the type double, which
causes tons of issues with int64_t types. Anyway, OPT_BYTE_SIZE is often
used as maximum for size_t quantities, which can have a size different
from (u)int64_t.
OPT_BYTE_SIZE still uses in64_t, because in theory, you could use it for
file sizes. (demux.c would for example be capable of caching more than
2GB on 32 bit platforms if a file cache is used. Though for some reason
the accounting code still uses size_t, so that use case is broken. But
still insist that it _could_ be used this way.)
There were various inconsistent attempts to set m_option.max to a value
such that the size_t/int64_t upper limit is not exceeded. Due to the
double max field, this didn't really work correctly. Try to fix this
with the M_MAX_MEM_BYTES constant. It's a good approximation, because on
32 bit it should allow 2GB (untested, also would probably exhaust
address space in practice but whatever), and something "high enough" in
64 bit.
For some reason, clang 11 still warns. But I think this might be a clang
bug, or I'm crazy. The result is correct anyway.
Change all OPT_* macros such that they don't define the entire m_option
initializer, and instead expand only to a part of it, which sets certain
fields. This requires changing almost every option declaration, because
they all use these macros. A declaration now always starts with
{"name", ...
followed by designated initializers only (possibly wrapped in macros).
The OPT_* macros now initialize the .offset and .type fields only,
sometimes also .priv and others.
I think this change makes the option macros less tricky. The old code
had to stuff everything into macro arguments (and attempted to allow
setting arbitrary fields by letting the user pass designated
initializers in the vararg parts). Some of this was made messy due to
C99 and C11 not allowing 0-sized varargs with ',' removal. It's also
possible that this change is pointless, other than cosmetic preferences.
Not too happy about some things. For example, the OPT_CHOICE()
indentation I applied looks a bit ugly.
Much of this change was done with regex search&replace, but some places
required manual editing. In particular, code in "obscure" areas (which I
didn't include in compilation) might be broken now.
In wayland_common.c the author of some option declarations confused the
flags parameter with the default value (though the default value was
also properly set below). I fixed this with this change.
Before this commit, option declarations used M_OPT_MIN/M_OPT_MAX (and
some other identifiers based on these) to signal whether an option had
min/max values. Remove these flags, and make it use a range implicitly
on the condition if min<max is true.
This requires care in all cases when only M_OPT_MIN or M_OPT_MAX were
set (instead of both). Generally, the commit replaces all these
instances with using DBL_MAX/DBL_MIN for the "unset" part of the range.
This also happens to fix some cases where you could pass over-large
values to integer options, which were silently truncated, but now cause
an error.
This commit has some higher potential for regressions.
Change to it 1000 hours, which is "infinite" enough. (Hesitant to use
INFINITY, as that is not in the option's range. The option parser
rejects it because it causes only problems in API users and so on.)
The demuxer cache employs a strange method to make track switching
instant with caching enabled. Normally this would mean you have to wait
until the cache has played out (and you get new packets, including
packets from the newly selected track), or you have to perform a slow
high level seek (decoding video again etc.). The strange method is that
it performs a demuxer-level seek without a high level seek so it looks
like a continuous stream to the decoder, and the newly select stream
gets packets at the current playback position. This is called a refresh
seek.
This works only if some weird heuristics work. It needs a packet "unique
ID", for which it uses either dts or pts. The value must be strictly
monotonic increasing. If this doesn't work, the referesh seek can't be
executed, and the user has to wait until the end of the cache. Sometimes
there are files that simply do not work.
In the present case, there's actually a hack that we can extend. Packets
with unset position are likely generated by the parser, and the hack
which this commit touches simply attempts to make up a new (hopefully
unique) position value, even if the value itself makes no sense. It only
ha to be deterministic.
It turns out libavcodec sometimes output packets with repeating position
values. This commit tries to handle this case too with the same hack.
Fixes: #7498
Preparation for a future commit. The demuxer queues might be read from
other threads than the one to issue the seek, and passing SEEK_BLOCK
with such a seek will provide a convenient way to synchronize this.
It seems sporadic errors are possible, such as connection timeouts.
Before the recent demuxer change, the demuxer thread retried many times
even on EOF, so an error was only interpreted as EOF once the decoder
queues ran out.
Change it to use EOF only. Since this may actually lead to the demuxer
thread being "stuck" and retrying forever (depending on libavformat API
behavior), I'm also adding a heuristic to prevent this, using a random
retry counter. This should not be necessary, but libavformat cannot be
trusted. (This retrying forever could be stopped by the user, but
obviously it would still heat the CPU for a longer time if the user is
not present.)
In this case the video track has seek_start == seek_end, and due to the
"seek_start >= seek_end" condition, this was considered broken, and no
seek range was created, breaking cached seeking.
Fix this by allowing the case if they're equal, and a valid timestamp.
(NB: seeking backward in this will still jump to position 0, because it
is the video timestamp. This is unfortunately how it's supposed to work.
HR-seeks will also do this, but decode and skip the entire audio until
the seek target, so it will mostly appear to work.)
Exposed by commit b56e2efd5f. demux_timeline reported a bogus EOF if
"parallel" streams were used. If a virtual source reported EOF, it was
propagated as global EOF, without serving packets of other virtual
sources that have not ended yet.
Fix this by not reporting global EOF just because a source has not
returned a packet. Instead make the reader retry by returning no packet
and no EOF state, which will call d_read_packet() again with a different
source. Rely on the eof_reached flags to signal global EOF.
Since eof_reached is now more important, set it in a certain other case
when it apparently should have been set. do_read_next_packet()'s return
value is now ignored, so get rid of it.
This is useful with live streams, and it's not much worse than the h264
first packet hack, which reads some data anyway.
For some reason, the option wasn't even documented, so do that.
In addition, print the start time even if it's negative. That should not
be possible, but for some reason, the field is an int64_t copied from an
uint64_t so... whatever. Keeping the logging slightly more straight
forward is better anyway.
Remove some redundant fields that controlled or indicated whether the
demuxer was/could/should prefetch. Redefine how the eof/reading fields
work.
The in->eof field is now always valid, instead of weirdly being reset to
false in random situations. The in->reading field now corresponds to
whether the demuxer thread is working at all, and is reset if it stops
doing anything.
Also, I always found it stupid that dequeue_packet() forced the demuxer
thread to retry reading if it was EOF. This makes little sense, but was
probably added for files that are being appended to (running downloads).
It makes no sense, because if the cache really tried to read until file
EOF, it would encounter partial packets and throw errors, so all is lost
anyway. Plus stream_file now handles this better. So stop this behavior,
but add a temporary option that enables the old behavior.
I think checking for ds->eager when enabling prefetching never really
made sense (could be debated, but no, not really). On the other hand,
the change above exposed a missing wakeup in the backward demuxing code.
Some chances of regressions that could make it stuck in certain states
or so, or incorrect demuxer cache state reporting to the player
frontend.
A negative subtitle delay means that subtitles from the future should be
shown earlier. With muxed subtitles, subtitle packets are demuxed along
with audio and video packets. But since they are demuxed "lazily",
nothing guarantees that subtitle packets from the future are available
in time.
Typically, the user-observed effect is that subtitles do not appear at
all (or too late) with large negative --sub-delay values, but that using
--cache might fix this.
Make this behave better. Automatically extend read-ahead to as much as
needed by the subtitles. It seems it's the easiest to pass the subtitle
render timestamp to the demuxer in order to guarantee that everything is
read. This timestamp based approach might be fragile, so disable it if
no negative sub-delay is used.
As far as the player frontend part is concerned, this makes use of the
code path for external subtitles, which are not lazily demuxed, and may
already trigger waiting.
Fixes: #7484
Subtitle tracks are usually "lazy" (ds->eager=false), There are a number
of weird special cases associated with it. One of them is that they have
some sort of "temporary" EOF (to signal that there isn't a packet right
now, and the decoder should not block playback by waiting for more
packets). In a the next commit, I want to call mark_stream_eof() in case
of (some) of these temporary EOFs.
The problem is that mark_stream_eof() also calls the functions touched
by this commit. Basically they shouldn't do any complex work due to
these temporary EOFs (because they might happen very often). It turns
out that lazy tracks barely matter here: they do not extend the seek
range of a packet/EOF happens on them, they do not trigger seek range
joining, and they do not support backward demuxing.
This change should enable the following commit, while not causing any
behavior changes (i.e. bugs) with the current state.
A parameter that is actually used is removed from the param_names[]
array, so we can report unused parameters. This also happened on
duplicate parameters, so adjust the warning to make it less confusing.
(In any case, you're not supposed to provide duplicate parameters.)
Until now, delay-loading was for files with single tracks only
(basically what DASH and HLS like to expose, so adaptive streaming and
codec selection becomes easier - for sites, not for us). But they also
provide some interleaved versions, probably for compatibility. Until
now, we were forced to eagerly load it (making startup slightly slower).
But there is not much missing. We just need a way to provide multiple
metadata entries, and use them to represent each track.
A side effect is now that the "track_meta" header can be used for normal
EDL files too.
RTSP supports seeking, but at least the libavformat implementation makes
this dependent on runtime behavior. So you have to perform a seek, and
check if it fails. But even if you do this, the stream is interrupted
and restarted, and there seem to be other issues.
Assume that RTSP with unknown duration means it's a live stream, and
disable seeking in this case, as suggested by the issue reporter.
Fixes: #7472
Now this was stupid. To seek a source, it obviously has to be opened...
so just don't try to seek any unused source. If the track is actually
selected during playback, a seek to the correct position is performed
anyway.
These have ->segmented set (so the codec can be initialized properly),
but have no segment start or end times. This code was (probably) the
only thing which didn't handle this case.
ytdl_hook.lua can do this with all_formats and when delay_open is used,
and if the source stream actually contains both audio and video. In this
case, it might accidentally hide a media type completely, or waste
bandwidth (if the stream has true interleaved audio/video). So it's
important to warn.
While paused, the decoders typically stop reading data from the demuxer.
But for some reason, the file size is returned as a public field in
struct demuxer (wat...), and updated only when the packet reading
function is called. This caused the file size property to always return
the same value when paused, even though the demuxer thread was reading
new data, and the internal file size was updated.
Fix with a simple hack.
Instead of every packet. Doing it every packet led to the performance
regression mentioned in the fstat() commit. This should now be over, but
out of being careful, don't query the file size that often. This is only
used for user interface things, so this should not cause any problems.
For the sake of leaving the code compact, abuse another thing that is
updated only every second (speed statistics).
Libav seems rather dead: no release for 2 years, no new git commits in
master for almost a year (with one exception ~6 months ago). From what I
can tell, some developers resigned themselves to the horrifying idea to
post patches to ffmpeg-devel instead, while the rest of the developers
went on to greener pastures.
Libav was a better project than FFmpeg. Unfortunately, FFmpeg won,
because it managed to keep the name and website. Libav was pushed more
and more into obscurity: while there was initially a big push for Libav,
FFmpeg just remained "in place" and visible for most people. FFmpeg was
slowly draining all manpower and energy from Libav. A big part of this
was that FFmpeg stole code from Libav (regular merges of the entire
Libav git tree), making it some sort of Frankenstein mirror of Libav,
think decaying zombie with additional legs ("features") nailed to it.
"Stealing" surely is the wrong word; I'm just aping the language that
some of the FFmpeg members used to use. All that is in the past now, I'm
probably the only person left who is annoyed by this, and with this
commit I'm putting this decade long problem finally to an end. I just
thought I'd express my annoyance about this fucking shitshow one last
time.
The most intrusive change in this commit is the resample filter, which
originally used libavresample. Since the FFmpeg developer refused to
enable libavresample by default for drama reasons, and the API was
slightly different, so the filter used some big preprocessor mess to
make it compatible to libswresample. All that falls away now. The
simplification to the build system is also significant.
Add something that will access an URL embedded in EDL only when the
track it corresponds to is actually selected. This is meant to help with
ytdl_hook.lua and to improve loading speeds.
In theory, all this stuff is available to any mpv user, but discourage
using it, as it's so specialized towards ytdl_hook.lua, that there's
danger we'll just break this once ytdl_hook.lua stops using it, or
similar.
Mostly untested.
Normally, the first sub-stream is implicitly created. This change lets
the user use more orthogonal syntax, and use a new_stream header for
every sub-stream, instead of having to skip the header for the first
one.
Accidentally broken by commit 99700bc52c. mp_path_join() does not
check for this, because it's supposed to work on filesystem strings (and
e.g. "http://fubar" is a valid relative path in UNIX).
Add a mp_log context to the parse_edl() function, and report some
errors. Previously, this just told you that something was wrong. Add
some error reporting to make it slightly less evil.
Put all parameters in a list before processing them. This makes adding
parameters for special headers easier, and we can report parameters that
were not understood. (For "compatibility", which probably doesn't matter
at all, still don't count them as errors; as before.)
The timeline stuff has messed up memory management because there are no
clear ownership rules between a some demuxer instances (master or
demux_timeline) and the timeline object itself.
This is another subtle problem that happened: apparently,
demux_timeline.open is supposed to take over ownership of timeline, but
only on success. If it fails, it's not supposed to free it. It didn't
follow this, which lead to a double-free if demux_timeline.open failed.
The failure path in demux.c calls both timeline_destroy() and
demux_timeline.close on failure.
Move them around in the source code to get rid of the forward
declarations. Other than rearranging the lines and removing the 2
forward declarations, there are no other changes at all.
Apparently such .cue files exist. They fail both probing and parsing. To
make it worse, the sample at hand was encoded as Latin1.
One part of this is replacing bstr_lstrip() with a version that supports
NBSP. One could argue that bstr_lstrip() should always do this, but I
don't want to overdo it. There are many more unicode abomination which
it could be said it's supposed to handle, so it will stay ASCII instead
of going down this rabbit hole. I'm just assuming this cue sheet was
generated by some stupid software that inexplicably liked NBSPs (which
is how we justify a one-off fix). The new lstrip_whitespace() doesn't
look particularly efficient, but it doesn't have to be.
The second part is dealing with the fact that the charset is not
necessarily UTF-8. We don't want to do conversion before probing thinks
it knows it's a cue sheet (would probably make it more fragile all
around), so just make it work with Latin1 by assuming invalid code
points are Latin1. This fallback is part of why lstrip_whitespace() is
sort of roundabout.
(You could still rewrite it as much more efficient state machine,
instead of using a slow and validating UTF-8 parser that is called per
codepoint. Starting to overthink this.)
Multimedia is terrible. Legacy charsets are terrible. Everything is
terrible.
Fixes: #7429
See manpage additions. The libarchive behavior mentioned in the last
paragraph there is technically unrelated, but makes this new option
mostly pointless.
See: #7182
Until now, they were all just added to options.c (e.g. demux_mkv_conf).
This adds a mechanism which can be used to add future options in a
(very) slightly more elegant way.
Instead of opening every volume on start just to see if it's there, all
all volumes that could possibly exist, and "handle" it on opening. This
requires working around some of libarchive's amazing stupidity and using
some empirically determined behavior. Will possibly break if libarchive
changes some of this behavior.
See: #7182
When switching tracks, the data for the new track is missing by the
amount of data prefetched. This is because all demuxers return
interleaved data, and you can't just seek the switched track alone.
Normally, this would mean that the new track simply gets no data for a
while (e.g. silence if it's an audio track). To avoid this, mpv performs
a special "refresh seek" in the demuxer, which tries to resume demuxing
from an earlier position, in a way that does not disrupt decoding for
the non-changed tracks. (Could write a lot about the reasons for doing
something so relatively complex, and the alternatives and their
weaknesses, but let's not.)
This requires that the demuxer can tell whether a packet after a seek
was before or after a previously demuxed packet, sort of like an unique
ID. The code can use the byte position (pos) and the DTS for this. The
DTS is normally strictly monotonically increasing, the position in most
sane file formats too (notably not mp4, in theory).
The file at hand had DTS==NOPTS packets (which is fine, usually this
happens when PTS can be used instead, but the demux.c code structure
doesn't make it easy to use this), and pos==-1 at the same time. The
latter is what libavformat likes to return when the packet was produced
by a "parser" (or in other words, packets were split or reassembled),
and the packet has no real file position. That means the refresh seek
mechanism has no packet position and can't work.
Fix this by making up a pseudo-position if it's missing. This needs to
set the same value every time, which is why it does not work for
keyframe packets (which, by definition, could be a seek target).
Fixes: #7306 (sort of)
Although a linked list was ideal at first, there are cases where it
sucks, and became increasingly awkward (with the mpv command API
preferring integer indexes to access the list). In future, we probably
want to add more playlist-related functionality, so better change it to
an array now.
An array isn't always ideal either. Since playlist entries are still
separate objects (because in some cases you need a stable "iterator" to
it), but you still need to efficiently get the next/previous playlist
entry, there's a pl_index field, that needs to be maintained. E.g.
adding an entry at the start of the playlist => update the pl_index
field for all other entries. Well, it's not really worth to do something
more complicated to avoid these things.
This commit is probably buggy as shit. It's not like I bothered to test
everything. That's _your_ role.
Demuxers can call demux_close_stream() to close the underlying stream if
it's not needed anymore. (Useful to release "heavy" resources like FDs
and sockets. Plus merely keeping a file open can have visible side
effects such as inability to unmount a filesystem or, on Windows, to do
anything with the file.)
Until now, this set demuxer->stream to a dummy stream, because most code
used to assume that the stream field is non-NULL. But this requirement
disappeared (in some cases, the stream field is already NULL), so stop
doing that. demux_lavf.c, one of the demuxers which calls this function,
still had some of this, though.
mf:// has an obscure feature that lets you pass a list of filenames
separated by newlines. Who knows whether anyone is using that. It opened
these listfiles with fopen(), so the recent stream origin bullshit
doesn't operate on it. Fix this by using the mpv internal stream API
instead. Unfortunately there is no fgets(), so write an ad-hoc one. (An
implementation of line reading via "stream" is still in demux_playlist,
but it's better to keep it quarantined there.)
Until now, .edl files accepted only "simple" filenames, i.e. no relative
or absolute paths, no URLs. Now that the origin bullshit is a bit
cleaned up and enforced in the EDL code, there's absolutely no reason to
keep this.
The new code behaves somewhat similar to playlists. (Although playlists
are special because they're not truly recursively opened.)
mpv has a very weak and very annoying policy that determines whether a
playlist should be used or not. For example, if you play a remote
playlist, you usually don't want it to be able to read local filesystem
entries. (Although for a media player the impact is small I guess.)
It's weak and annoying as in that it does not prevent certain cases
which could be interpreted as bad in some cases, such as allowing
playlists on the local filesystem to reference remote URLs. It probably
barely makes sense, but we just want to exclude some other "definitely
not a good idea" things, all while playlists generally just work, so
whatever.
The policy is:
- from the command line anything is played
- local playlists can reference anything except "unsafe" streams
("unsafe" means special stream inputs like libavfilter graphs)
- remote playlists can reference only remote URLs
- things like "memory://" and archives are "transparent" to this
This commit does... something. It replaces the weird stream flags with a
slightly clearer "origin" value, which is now consequently passed down
and used everywhere. It fixes some deviations from the described policy.
I wanted to force archives to reference only content within them, but
this would probably have been more complicated (or required different
abstractions), and I'm too lazy to figure it out, so archives are now
"transparent" (playlists within archives behave the same outside).
There may be a lot of bugs in this.
This is unfortunately a very noisy commit because:
- every stream open call now needs to pass the origin
- so does every demuxer open call (=> params param. gets mandatory)
- most stream were changed to provide the "origin" value
- the origin value needed to be passed along in a lot of places
- I was too lazy to split the commit
Fixes: #7274
This has the advantage that playlists within the archive will work as
expected, because demux_playlist will correctly join the archive base
URL and entry name. Before this change, it could skip before the "|",
resulting in a broken URL.
EDL files can have multiple segments taken from the same source file. In
this case, the source file is supposed to be opened only once. This
stopped working, and it created a new demuxer instance for every single
segment entry. This made it slow and made it use much more memory than
needed.
This was because it tried to iterate over the array of source files, but
the array count (num_parts) was only set to a non-0 value later. Fix
this by maintaining the count correctly.
In addition, the actual code for checking whether a source can be reused
(in open_source()) regressed and stopped working correctly. d->stream
could be NULL. Use demuxer.filename instead; I'm not entirely sure
whether this is always correct, but fortunately we have a distributed
almost-AI driven test suite (called "users") which will probably find
and report such cases.
Probably broke with commit a09396ee60 or something close, but didn't
check closer.
Fixes: #7267
See previous commit. libavformat exports this information as AVStream.id
field.
The big problem is that the libavformat field is simply 0 if it's
unknown (i.e. the demuxer never sets it). So it needs to remain a
whitelist. Just add more formats which are known to have a meaningful
ID.
I considered exporting IDs for all formats, and then either leaving the
values as they are, or filtering duplicate values (and choosing
arbitrary but unique different IDs). But then again, I think it's sort
of mpv's job to filter FFmpeg's absurd bullshit API, and it should make
an effort to hide it rather than to reflect it.
See: #7211
The demuxer_id (exported in as "src-id" property) is supposed to be the
native stream ID, as it exists in the file, or -1 if that does not exist
(actually any negative value), or if it is unknown.
Until now, an ID was made up if it was missing. That seems like strange
non-sense, and I can't find the reason why it was done. But it was
probably for convenience by the EDL stuff or so.
Stop doing this. Fortunately, the src-id property was documented as
being unavailable if the ID is not known. Even the code for this was
present, it was just inactive until now. Extend input.rst with some
explanations.
Also fixing 3 other places where negative demuxer_id was ignored or
avoided.
Just an implementation detail that can be cleaned up now. Internally,
m_config maintains a tree of m_sub_options structs, except for the root
it was not defined explicitly. GLOBAL_CONFIG was a hack to get access to
it anyway. Define it explicitly instead.
If SEEK_FORWARD is set, a demuxer should skip to the next frame if the
timestamp does not fall on the start of a frame. If that flag is not
set, it should always seek to the first frame before the target
timestamp (or the first frame in the file).
It sometimes happens that HLS streams freeze because the HTTP server is
not responding for a fragment (or something similar, the exact
circumstances are unknown). The --timeout option didn't affect this,
because it's never set on HLS recursive connections (these download the
fragments, while the main connection likely nothing and just wastes a
TCP socket).
Apply an elaborate hack on top of an existing elaborate hack to somehow
get these options set. Of course this could still break easily, but hey,
it's ffmpeg, it can't not try to fuck you over. I'm so fucking sick of
ffmpeg's API bullshit, especially wrt. HLS.
Of course the change is sort of pointless. For HLS, GET requests should
just aggressively retried (because they're not "streamed", they're just
actual files on a CDN), while normal HTTP connections should probably
not be made this fragile (they could be streamed, i.e. they are backed
by some sort of real time encoder, and block if there is no data yet).
The 1 minute default timeout is too high to save playback if this
happens with HLS.
Vaguely related to #5793.
Until now, we've made FFmpeg use the default network timeout - which is
apparently infinite. I don't know if this was changed at some point,
although it seems likely, as I was sure there was a more useful default.
For most use cases, a smaller timeout is more useful (for example
recording something in the background), so force a timeout of 1 minute.
See: #5793
stream_skip() semantics were kind of bad, especially after the recent
change to the stream code. Forward stream_skip() calls could still
trigger a seek and fail, even if it was supposed to actually skip data.
(Maybe the idea that stream_skip() should try to seek is worthless in
the first place.)
Rename it to stream_seek_skip() (takes absolute position now because I
think that's better), and make it always skip if the stream is marked as
forward.
While we're at it, make EOF detection more robust. I guess s->eof
shouldn't exist at all, since it's valid only "sometimes". It should be
removed... but not today. A 1-byte stream_read_peek() call is good to
get the s->eof flag set to a correct value.
demux_mkv was the only thing using this, and everything else accessed it
directly. No need to keep the indirection wrapper around.
(Funny how this getter was in the initial commit of MPlayer.)
In some corner cases (see #6802), it can be beneficial to use a larger
stream buffer size. Use this as argument to rewrite everything for no
reason.
Turn stream.c itself into a ring buffer, with configurable size. The
latter would have been easily achievable with minimal changes, and the
ring buffer is the hard part. There is no reason to have a ring buffer
at all, except possibly if ffmpeg don't fix their awful mp4 demuxer, and
some subtle issues with demux_mkv.c wanting to seek back by small
offsets (the latter was handled with small stream_peek() calls, which
are unneeded now).
In addition, this turns small forward seeks into reads (where data is
simply skipped). Before this commit, only stream_skip() did this (which
also mean that stream_skip() simply calls stream_seek() now).
Replace all stream_peek() calls with something else (usually
stream_read_peek()). The function was a problem, because it returned a
pointer to the internal buffer, which is now a ring buffer with
wrapping. The new function just copies the data into a buffer, and in
some cases requires callers to dynamically allocate memory. (The most
common case, demux_lavf.c, required a separate buffer allocation anyway
due to FFmpeg "idiosyncrasies".) This is the bulk of the demuxer_*
changes.
I'm not happy with this. There still isn't a good reason why there
should be a ring buffer, that is complex, and most of the time just
wastes half of the available memory. Maybe another rewrite soon.
It also contains bugs; you're an alpha tester now.
The old code made it depend on ->seekable. If it isn't seekable, and
something discarded the data, then it'll just show an error message,
which will at least be somewhat informative. If no data was discarded,
the seek call is always a no-op.
There's a weird "timeline" condition in the old code; this doesn't
matter anymore, because timeline stuff does not pass streams down to
nested demuxers anymore.
demux_mkv has lots of logging that shows information about the file. It
sort of reminds of mkvinfo output. While this is sometimes interesting,
it's too much for verbose mode, and should be in debug log level.
This can be used by distros to disable all known FFmpeg ABI violations.
Currently only 1 is known, in demux_lavf.c. In addition to if-defing out
the access to the private FFmpeg field, this disables the possibly
fragile nested open callbacks, which make sense only if the
aforementioned field can be accessed.
In pseudo-DASH mode, we may have no real streams opened until the
demuxer layer is fully loaded and playback actually starts. The only
hint that the stream is from network is, at that point, the init
segment, which is only opened as stream, and then separately as demuxer
(which is dumb but happened to fit the internal architecture better).
So just propagate the flags from the init segment stream. Seems like an
annoyance, but doesn't hurt that much I guess. (Until someone gets the
idea to pass the init segment data inline or so, but nothing does that.)
The sample link in the linked issue will probably soon switch to another
format, because that service always does this after recent uploads or
so.
Fixes: #7038
Someone crazy is trying to mix images with videos in EDL files. Putting
an image as first thing into the EDL disabled audio, because the first
EDL entry was used to define the layout.
Change this. Make it user-configurable, and use a "better" heuristic to
select the default otherwise.
In theory, EDL could be easily extended to specify track layout and
mapping of parts to virtual EDL tracks manually and in great detail. But
I don't think it's worth it - who would bother using it?
Fixes: #6764
This partially reverts commit a9d83eac40
("Remove optical disc fancification layers").
Mostly due to the timestamp crap, this was never really going to work.
The playback layer is sensitive to timestamps, and derives the playback
time directly from the low level packet timestamps. DVD/BD works
differently, and libdvdnav/libbluray do not make it easy at all to
compensate for this. Which is why it never worked well, but not doing it
at all is even more awful.
demux_disc.c tried this and rewrote packet timestamps from low level TS
to playback time. So restore demux_disc.c, which should bring behavior
back to the old often non-working but slightly better state.
I did not revert anything that affects components above the demuxer
layer. For example, the properties for switching DVD angles or listing
disc titles are still gone. (Disc titles could be reimplemented as
editions. But not by me.)
This commit modifies the reverted code a bit; this can't be avoided,
because the internal API changed quite a bit. The old seek resync in
demux_lavf.c (which was a hack) is replaced with a hack. SEEK_FORCE and
demux_params.external_stream are new additions.
Some of this could/should be further cleaned up. If you don't want
"proper" DVD/BD support to disappear, you should probably volunteer.
Now why am I wasting my time for this? Just because some idiot users are
too lazy to rip their ever-wearing out shitty physical discs? Then why
should I not be lazy and drop support completely? They won't even be
thankful for me maintaining this horrible garbage for no compensation.
This was added in 585f9ff42f by @bbarenblat (github handle). We
don't do this. This file alone probably has multiple dozen of authors (I
didn't count, but it has a history of 15 years). If everyone added their
names with each small change, this project would have giant lists of
contributing authors on every source file.
Neither copyright law nor any of the used licenses require listing
authors in the license header. Authorship is recorded in the git log.
So don't start with this, and remove this recent case to avoid setting a
precedent.
Some files still have an author in the header. These cases are
grandfathered, and usually are the actual authors of the original code.
demux_mkv may seek to the end of the file to read certain headers (which
should probably be called "footers", but in theory they are just headers
that have been placed at the end of the file unfortunately).
This commit changes behavior not to seek if the stream is not marked as
seekable. Before this, it only checked whether the stream size was
unknown (end negative). In practice it doesn't make much of a
difference, since seekable usually equals known stream size.
Also improve the wording, and distinguish between actual incomplete
files, and unseekable ones.
This passed all streams to mp_recorder_create(), even disabled ones. The
disabled streams never get packets, so recorder.c eventually errors out
with unrelated-looking errors. The reason is that recorder.c waits for
packets to appear on other streams, which in turn is because libavformat
refuses to mux empty streams anyway.
recorder.c could call demux_stream_is_selected(), which would have made
the patch much smaller. But this feels like a bad idea, since recorder.c
should use sh_stream only for metadata (and not in an "active" way), nor
should it care what demux.c is currently doing with it. So make the API
user (demux.c) pass only the streams it really wants.
Fixes: #6999
Although this was sort of elegant, it just seems to complicate things
slightly. Originally, the API meant that you cache mp_recorder_sink
yourself (which would avoid the mess of passing an index around), but
that too seems slightly roundabout.
In a later change, I want to change the set of streams passed to
mp_recorder_create(), and then I'd have to keep track of the index for
each stream, which would suck. With this commit, I can just pass the
unambiguous sh_stream to it, and it will be guaranteed to match the
correct stream.
The disadvantages are barely worth discussing. It's a new linear search
per packet, but usually only 2 to 4 streams are active at a time. Also,
in theory a user could want to write 2 streams using the same sh_stream
(same metadata, just writing different packets or so), but in practice
this is never done.
in->eof is used as an indicator whether reading packets still makes
sense. (Without this, the prefetcher would obviously burn CPU by
retrying reading even though everything has been read.)
This was not reset properly after seeks were performed. It led to
getting stuck in at least one corner case: when enabling a track, the
demuxer would seek backwards to get new packets from the current
playback position ("refresh seeks"). But if playback was paused, and EOF
was previously reached, it would not try to read packers again due to
in->eof being false. There was not anything else that would make it
retry reading, so it was stuck in a weird underrun/buffering state.
Fixes: #6986
This was a leftover from commit b2752321 which fixed#6522 but after
the recent demux refactoring this fix is superseded by commit 0f6cda4ab.
Remove the redundant update call.
This detected the first packet demuxed after a seek as timestamp
discontinuity. Obviously this is non-sense. Since the OGG radio streams
for which this feature was introduced are normally unseekable, it's
simple to fix this: simply disable it (if in auto mode, the default) as
soon as a seek is performed. This code is never called if the stream is
considered unseekable, unless the user forced it.
There's still a chance this linearization is performed before a seek
happens. This will be a bit awkward, but no worse than without this
feature, since seeking with timestamp resets is inherently broken in
both mpv and libavformat.
Fixes: #6974
Fixes: 27fcd4d
Before this commit, EDL or CUE files did not properly enable the cache
if they were on "slow" media (stream->streaming==true). This happened
because the stream is unset for demux_timeline, so the streaming flag
could not be queried anymore.
Fix this by adding this flag to struct demuxer, and propagate it exactly
like the is_network flag. is_network is not used for checking the cache
options anymore, and its main function seems to be something else.
Normal http streams set the streaming flag already.
This should fix#6958.
This field is documented as internal, so an API user should not
access it. However, this is the only way to get some read statistics
without replacing FFmpeg's entire HLS demuxer. (Using custom I/O as
workaround doesn't work: the HLS code uses some weird internal APIs
that cannot be provided by FFmpeg API users; I even made the author
of the relevant patch to provide a public API, but which was shot
down by another FFmpeg developer. So I take this as my right to
access this field.)
Mention this explicitly, as it affects ABI and API compatibility, and
I don't want that anyone claims this was a "mistake". Add some
explanations.
In theory, a 0 size allocation could have made it memset() on a NULL
pointer (with a non-0 size, which makes it crash in addition to
theoretical UB).
This should never happen, since even packets with size 0 should have an
associated allocation, as FFmpeg currently does. But avoiding this makes
the API slightly more orthogonal and less tricky, I guess.
This reverts commit 95636c65e7.
This change shouldn't be needed, and in fact it's wrong. The FFmpeg API
function could do anything it wants with the packet, including changing
the packet data pointer. Likewise, it's not guaranteed that the
referenced packet's fields mirror the current state of the mpv packet
struct (the AVPacket is only kept for the AVBuffer and the side data
stuff).
Helper for the ab-loop-dump-cache command, see manpage additions.
This is kind of shit. Not only is this a very "special" feature, but it
also vomits more messy code into the big and already bloated demux.c,
and the implementation is sort of duplicated with the dump-cache code.
(Except it's different.) In addition, the results sort of depend what a
video player would do with the dump-cache output, or what the user wants
(for example, a user might be more interested in the range of output
audio, instead of the video).
But hey, I don't actually need to justify it. I'm only justifying it for
fun.
That's right, and it's probably not the end of it. I'll just claim that
I have no idea how to create a proper user interface for this, so I'm
creating multiple partially-orthogonal, of which some may work better in
each of its special use cases.
Until now, there was --record-file. You get relatively good control
about what is muxed, and it can use the cache. But it sucks that it's
bound to playback. If you pause while it's set, muxing stops. If you
seek while it's set, the output will be sort-of trashed, and that's by
design.
Then --stream-record was added. This is a bit better (especially for
live streams), but you can't really control well when muxing stops or
ends. In particular, it can't use the cache (it just dumps whatever the
underlying demuxer returns).
Today, the idea is that the user should just be able to select a time
range to dump to a file, and it should not affected by the user seeking
around in the cache. In addition, the stream may still be running, so
there's some need to continue dumping, even if it's redundant to
--stream-record.
One notable thing is that it uses the async command shit. Not sure
whether this is a good idea. Maybe not, but whatever. Also, a user can
always use the "async" prefix to pretend it doesn't.
Much of this was barely tested (especially the reinterleaving crap),
let's just hope it mostly works. I'm sure you can tolerate the one or
other crash?
It makes some slight sense and helps with one of the following commits.
Also rename that other function to make it sound less similar to
find_seek_target().
