2011-08-20 17:25:43 +00:00
|
|
|
/*
|
2015-04-13 07:36:54 +00:00
|
|
|
* This file is part of mpv.
|
2011-08-20 17:25:43 +00:00
|
|
|
*
|
2017-04-21 11:33:23 +00:00
|
|
|
* mpv is free software; you can redistribute it and/or
|
|
|
|
|
* modify it under the terms of the GNU Lesser General Public
|
|
|
|
|
* License as published by the Free Software Foundation; either
|
|
|
|
|
* version 2.1 of the License, or (at your option) any later version.
|
2011-08-20 17:25:43 +00:00
|
|
|
*
|
2015-04-13 07:36:54 +00:00
|
|
|
* mpv is distributed in the hope that it will be useful,
|
2011-08-20 17:25:43 +00:00
|
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
|
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
2017-04-21 11:33:23 +00:00
|
|
|
* GNU Lesser General Public License for more details.
|
2011-08-20 17:25:43 +00:00
|
|
|
*
|
2017-04-21 11:33:23 +00:00
|
|
|
* You should have received a copy of the GNU Lesser General Public
|
|
|
|
|
* License along with mpv. If not, see <http://www.gnu.org/licenses/>.
|
2011-08-20 17:25:43 +00:00
|
|
|
*/
|
|
|
|
|
|
|
|
|
|
#ifndef MPLAYER_DEMUX_PACKET_H
|
|
|
|
|
#define MPLAYER_DEMUX_PACKET_H
|
|
|
|
|
|
2012-07-24 21:23:27 +00:00
|
|
|
#include <stdbool.h>
|
2014-07-05 14:45:28 +00:00
|
|
|
#include <stddef.h>
|
2013-11-18 17:46:44 +00:00
|
|
|
#include <inttypes.h>
|
2011-08-20 17:25:43 +00:00
|
|
|
|
|
|
|
|
// Holds one packet/frame/whatever
|
|
|
|
|
typedef struct demux_packet {
|
|
|
|
|
double pts;
|
2013-11-25 22:13:01 +00:00
|
|
|
double dts;
|
2011-08-20 17:25:43 +00:00
|
|
|
double duration;
|
2016-02-15 19:39:17 +00:00
|
|
|
int64_t pos; // position in source file byte stream
|
2019-05-16 14:20:45 +00:00
|
|
|
|
|
|
|
|
unsigned char *buffer;
|
|
|
|
|
int len;
|
|
|
|
|
|
2018-09-07 13:12:24 +00:00
|
|
|
int stream; // source stream index (typically sh_stream.index)
|
2016-02-15 19:39:17 +00:00
|
|
|
|
2019-05-16 14:20:45 +00:00
|
|
|
bool keyframe;
|
|
|
|
|
|
Implement backwards playback
See manpage additions. This is a huge hack. You can bet there are shit
tons of bugs. It's literally forcing square pegs into round holes.
Hopefully, the manpage wall of text makes it clear enough that the whole
shit can easily crash and burn. (Although it shouldn't literally crash.
That would be a bug. It possibly _could_ start a fire by entering some
sort of endless loop, not a literal one, just something where it tries
to do work without making progress.)
(Some obvious bugs I simply ignored for this initial version, but
there's a number of potential bugs I can't even imagine. Normal playback
should remain completely unaffected, though.)
How this works is also described in the manpage. Basically, we demux in
reverse, then we decode in reverse, then we render in reverse.
The decoding part is the simplest: just reorder the decoder output. This
weirdly integrates with the timeline/ordered chapter code, which also
has special requirements on feeding the packets to the decoder in a
non-straightforward way (it doesn't conflict, although a bugmessmass
breaks correct slicing of segments, so EDL/ordered chapter playback is
broken in backward direction).
Backward demuxing is pretty involved. In theory, it could be much
easier: simply iterating the usual demuxer output backward. But this
just doesn't fit into our code, so there's a cthulhu nightmare of shit.
To be specific, each stream (audio, video) is reversed separately. At
least this means we can do backward playback within cached content (for
example, you could play backwards in a live stream; on that note, it
disables prefetching, which would lead to losing new live video, but
this could be avoided).
The fuckmess also meant that I didn't bother trying to support
subtitles. Subtitles are a problem because they're "sparse" streams.
They need to be "passively" demuxed: you don't try to read a subtitle
packet, you demux audio and video, and then look whether there was a
subtitle packet. This means to get subtitles for a time range, you need
to know that you demuxed video and audio over this range, which becomes
pretty messy when you demux audio and video backwards separately.
Backward display is the most weird (and potentially buggy) part. To
avoid that we need to touch a LOT of timing code, we negate all
timestamps. The basic idea is that due to the navigation, all
comparisons and subtractions of timestamps keep working, and you don't
need to touch every single of them to "reverse" them.
E.g.:
bool before = pts_a < pts_b;
would need to be:
bool before = forward
? pts_a < pts_b
: pts_a > pts_b;
or:
bool before = pts_a * dir < pts_b * dir;
or if you, as it's implemented now, just do this after decoding:
pts_a *= dir;
pts_b *= dir;
and then in the normal timing/renderer code:
bool before = pts_a < pts_b;
Consequently, we don't need many changes in the latter code. But some
assumptions inhererently true for forward playback may have been broken
anyway. What is mainly needed is fixing places where values are passed
between positive and negative "domains". For example, seeking and
timestamp user display always uses positive timestamps. The main mess is
that it's not obvious which domain a given variable should or does use.
Well, in my tests with a single file, it suddenly started to work when I
did this. I'm honestly surprised that it did, and that I didn't have to
change a single line in the timing code past decoder (just something
minor to make external/cached text subtitles display). I committed it
immediately while avoiding thinking about it. But there really likely
are subtle problems of all sorts.
As far as I'm aware, gstreamer also supports backward playback. When I
looked at this years ago, I couldn't find a way to actually try this,
and I didn't revisit it now. Back then I also read talk slides from the
person who implemented it, and I'm not sure if and which ideas I might
have taken from it. It's possible that the timestamp reversal is
inspired by it, but I didn't check. (I think it claimed that it could
avoid large changes by changing a sign?)
VapourSynth has some sort of reverse function, which provides a backward
view on a video. The function itself is trivial to implement, as
VapourSynth aims to provide random access to video by frame numbers (so
you just request decreasing frame numbers). From what I remember, it
wasn't exactly fluid, but it worked. It's implemented by creating an
index, and seeking to the target on demand, and a bunch of caching. mpv
could use it, but it would either require using VapourSynth as demuxer
and decoder for everything, or replacing the current file every time
something is supposed to be played backwards.
FFmpeg's libavfilter has reversal filters for audio and video. These
require buffering the entire media data of the file, and don't really
fit into mpv's architecture. It could be used by playing a libavfilter
graph that also demuxes, but that's like VapourSynth but worse.
2019-05-18 00:10:51 +00:00
|
|
|
// backward playback
|
|
|
|
|
bool back_restart; // restart point (reverse and return previous frames)
|
|
|
|
|
bool back_preroll; // initial discarded frame for smooth decoder reinit
|
|
|
|
|
|
Rewrite ordered chapters and timeline stuff
This uses a different method to piece segments together. The old
approach basically changes to a new file (with a new start offset) any
time a segment ends. This meant waiting for audio/video end on segment
end, and then changing to the new segment all at once. It had a very
weird impact on the playback core, and some things (like truly gapless
segment transitions, or frame backstepping) just didn't work.
The new approach adds the demux_timeline pseudo-demuxer, which presents
an uniform packet stream from the many segments. This is pretty similar
to how ordered chapters are implemented everywhere else. It also reminds
of the FFmpeg concat pseudo-demuxer.
The "pure" version of this approach doesn't work though. Segments can
actually have different codec configurations (different extradata), and
subtitles are most likely broken too. (Subtitles have multiple corner
cases which break the pure stream-concatenation approach completely.)
To counter this, we do two things:
- Reinit the decoder with each segment. We go as far as allowing
concatenating files with completely different codecs for the sake
of EDL (which also uses the timeline infrastructure). A "lighter"
approach would try to make use of decoder mechanism to update e.g.
the extradata, but that seems fragile.
- Clip decoded data to segment boundaries. This is equivalent to
normal playback core mechanisms like hr-seek, but now the playback
core doesn't need to care about these things.
These two mechanisms are equivalent to what happened in the old
implementation, except they don't happen in the playback core anymore.
In other words, the playback core is completely relieved from timeline
implementation details. (Which honestly is exactly what I'm trying to
do here. I don't think ordered chapter behavior deserves improvement,
even if it's bad - but I want to get it out from the playback core.)
There is code duplication between audio and video decoder common code.
This is awful and could be shareable - but this will happen later.
Note that the audio path has some code to clip audio frames for the
purpose of codec preroll/gapless handling, but it's not shared as
sharing it would cause more pain than it would help.
2016-02-15 20:04:07 +00:00
|
|
|
// segmentation (ordered chapters, EDL)
|
demux: get rid of demux_packet.new_segment field
The new_segment field was used to track the decoder data flow handler of
timeline boundaries, which are used for ordered chapters etc. (anything
that sets demuxer_desc.load_timeline). This broke seeking with the
demuxer cache enabled. The demuxer is expected to set the new_segment
field after every seek or segment boundary switch, so the cached packets
basically contained incorrect values for this, and the decoders were not
initialized correctly.
Fix this by getting rid of the flag completely. Let the decoders instead
compare the segment information by content, which is hopefully enough.
(In theory, two segments with same information could perhaps appear in
broken-ish corner cases, or in an attempt to simulate looping, and such.
I preferred the simple solution over others, such as generating unique
and stable segment IDs.)
We still add a "segmented" field to make it explicit whether segments
are used, instead of doing something silly like testing arbitrary other
segment fields for validity.
Cached seeking with timeline stuff is still slightly broken even with
this commit: the seek logic is not aware of the overlap that segments
can have, and the timestamp clamping that needs to be performed in
theory to account for the fact that a packet might contain a frame that
is always clipped off by segment handling. This can be fixed later.
2017-10-24 17:33:01 +00:00
|
|
|
bool segmented;
|
|
|
|
|
struct mp_codec_params *codec; // set to non-NULL iff segmented is set
|
|
|
|
|
double start, end; // set to non-NOPTS iff segmented is set
|
Rewrite ordered chapters and timeline stuff
This uses a different method to piece segments together. The old
approach basically changes to a new file (with a new start offset) any
time a segment ends. This meant waiting for audio/video end on segment
end, and then changing to the new segment all at once. It had a very
weird impact on the playback core, and some things (like truly gapless
segment transitions, or frame backstepping) just didn't work.
The new approach adds the demux_timeline pseudo-demuxer, which presents
an uniform packet stream from the many segments. This is pretty similar
to how ordered chapters are implemented everywhere else. It also reminds
of the FFmpeg concat pseudo-demuxer.
The "pure" version of this approach doesn't work though. Segments can
actually have different codec configurations (different extradata), and
subtitles are most likely broken too. (Subtitles have multiple corner
cases which break the pure stream-concatenation approach completely.)
To counter this, we do two things:
- Reinit the decoder with each segment. We go as far as allowing
concatenating files with completely different codecs for the sake
of EDL (which also uses the timeline infrastructure). A "lighter"
approach would try to make use of decoder mechanism to update e.g.
the extradata, but that seems fragile.
- Clip decoded data to segment boundaries. This is equivalent to
normal playback core mechanisms like hr-seek, but now the playback
core doesn't need to care about these things.
These two mechanisms are equivalent to what happened in the old
implementation, except they don't happen in the playback core anymore.
In other words, the playback core is completely relieved from timeline
implementation details. (Which honestly is exactly what I'm trying to
do here. I don't think ordered chapter behavior deserves improvement,
even if it's bad - but I want to get it out from the playback core.)
There is code duplication between audio and video decoder common code.
This is awful and could be shareable - but this will happen later.
Note that the audio path has some code to clip audio frames for the
purpose of codec preroll/gapless handling, but it's not shared as
sharing it would cause more pain than it would help.
2016-02-15 20:04:07 +00:00
|
|
|
|
2016-02-15 19:39:17 +00:00
|
|
|
// private
|
2011-08-20 17:25:43 +00:00
|
|
|
struct demux_packet *next;
|
2016-02-15 19:39:17 +00:00
|
|
|
struct AVPacket *avpacket; // keep the buffer allocation and sidedata
|
2017-11-04 22:02:25 +00:00
|
|
|
double kf_seek_pts; // demux.c internal: seek pts for keyframe range
|
demux: support for some kinds of timed metadata
This makes ICY title changes show up at approximately the correct time,
even if the demuxer buffer is huge. (It'll still be wrong if the stream
byte cache contains a meaningful amount of data.)
It should have the same effect for mid-stream metadata changes in e.g.
OGG (untested).
This is still somewhat fishy, but in parts due to ICY being fishy, and
FFmpeg's metadata change API being somewhat fishy. For example, what
happens if you seek? With FFmpeg AVFMT_EVENT_FLAG_METADATA_UPDATED and
AVSTREAM_EVENT_FLAG_METADATA_UPDATED we hope that FFmpeg will correctly
restore the correct metadata when the first packet is returned.
If you seke with ICY, we're out of luck, and some audio will be
associated with the wrong tag until we get a new title through ICY
metadata update at an essentially random point (it's mostly inherent to
ICY). Then the tags will switch back and forth, and this behavior will
stick with the data stored in the demuxer cache. Fortunately, this can
happen only if the HTTP stream is actually seekable, which it usually is
not for ICY things. Seeking doesn't even make sense with ICY, since you
can't know the exact metadata location. Basically ICY metsdata sucks.
Some complexity is due to a microoptimization: I didn't want additional
atomic accesses for each packet if no timed metadata is used. (It
probably doesn't matter at all.)
2018-04-16 20:23:08 +00:00
|
|
|
struct mp_packet_tags *metadata; // timed metadata (demux.c internal)
|
2011-08-20 17:25:43 +00:00
|
|
|
} demux_packet_t;
|
|
|
|
|
|
2017-11-05 15:36:18 +00:00
|
|
|
struct AVBufferRef;
|
|
|
|
|
|
2014-07-05 14:45:28 +00:00
|
|
|
struct demux_packet *new_demux_packet(size_t len);
|
2014-08-24 15:45:28 +00:00
|
|
|
struct demux_packet *new_demux_packet_from_avpacket(struct AVPacket *avpkt);
|
2014-07-05 14:45:28 +00:00
|
|
|
struct demux_packet *new_demux_packet_from(void *data, size_t len);
|
2017-11-05 15:36:18 +00:00
|
|
|
struct demux_packet *new_demux_packet_from_buf(struct AVBufferRef *buf);
|
2014-07-05 14:45:28 +00:00
|
|
|
void demux_packet_shorten(struct demux_packet *dp, size_t len);
|
|
|
|
|
void free_demux_packet(struct demux_packet *dp);
|
|
|
|
|
struct demux_packet *demux_copy_packet(struct demux_packet *dp);
|
2017-04-14 17:19:44 +00:00
|
|
|
size_t demux_packet_estimate_total_size(struct demux_packet *dp);
|
2014-07-05 14:45:28 +00:00
|
|
|
|
2015-02-05 20:52:07 +00:00
|
|
|
void demux_packet_copy_attribs(struct demux_packet *dst, struct demux_packet *src);
|
|
|
|
|
|
2014-11-03 19:00:34 +00:00
|
|
|
int demux_packet_set_padding(struct demux_packet *dp, int start, int end);
|
2017-01-31 13:48:10 +00:00
|
|
|
int demux_packet_add_blockadditional(struct demux_packet *dp, uint64_t id,
|
|
|
|
|
void *data, size_t size);
|
2014-11-03 19:00:34 +00:00
|
|
|
|
2011-08-20 17:25:43 +00:00
|
|
|
#endif /* MPLAYER_DEMUX_PACKET_H */
|
