So snd_device_name_get_hint() return values do in fact have to be freed.
Also, change listing semantics slightly: if io==NULL, skip the entry,
instead of assuming it's an output device.
Replace all the check macros with function calls. Give them all the
same case and naming schema.
Drop af_fmt2bits(). Only af_fmt2bps() survives as af_fmt_to_bytes().
Introduce af_fmt_is_pcm(), and use it in situations that used
!AF_FORMAT_IS_SPECIAL. Nobody really knew what a "special" format
was. It simply meant "not PCM".
So apparently, this essentially happens when the kernel driver doesn't
implement write accesses in the channel map control. Which doesn't
necessarily mean that the channel map is unsupported, or that there is a
bug - it's just lazyness and a consequence of the terrible ALSA kernel
API for the channel mapping stuff.
In these cases, the channel count implicitly selects the channel map,
and snd_pcm_set_chmap() always fails with ENXIO.
I'm actually not sure what happens if dmix is on top of e.g. HDMI, which
actually lets you change the channel mapping.
I'm also not sure why commit d20e24e5d1614354e9c8195ed0b11fe089c489e4
(alsa-lib git repository) does not take care of this.
They are useless. Not only are they actually rarely in use; but
libavcodec doesn't even output them, as libavcodec has no such sample
formats for decoded audio.
Even if it should happen that we actually still need them (e.g. if doing
direct hardware output), there are better solutions. Swapping the sign
is a fast and lossless operation and can be done inplace, so AO actually
needing it could do this directly.
If you wonder why we keep U8 instead of S8: because libavcodec does it.
Channel maps reported by the device as SND_CHMAP_TYPE_VAR can be freely
reordered. We don't use this much (out of laziness), but in this case
it's a simple way to reduce necessary reordering (which would be an
extra libavresample invocation), and to make debug output more readable.
If you try to play surround with dmix, it will advertise surround and
lets you set more than 2 channels, but will report a stereo channel map,
with the extra channels identified as NA. We could handle this now, but
we don't want to (because it's excessively stupid).
Do it only if the channel map is not what we requested, instead of just
acting if it contains NA entries at all. This avoids that we hurt
ourselves in the unlikely but possible case we actually have to use
channel maps with NA entries.
Sometimes, ALSA will return channel layouts with padded channels (NA
speakers). Use them instead of failing.
This still includes the old "braindeath" code to retry with a layout
without NA channels. This might be helpful for performance, and also the
padded channel layout string looks confusing.
To be fair, I have not encountered a case yet which would really need
this, and for which the old "braindeath" code did not fix it.
mp_chmap_from_channels_alsa() doesn't always succeed - there are a bunch
of channel counts for which no defined ALSA layout exists. Fallback to
stereo in this case. (Normally, this code path shouldn't happen at all.)
Silence the usually user-visible warning about unsupported channel maps.
This might be an ALSA bug, but ALSA will never fix this behavior anyway.
(Or maybe it's a feature.)
Log some other information that might be useful.
Apparently, physically disconnecting the audio device (consider USB
audio) breaks the ALSA device handle forever. It will signal ENODEV.
Fortunately, it's easy for us to handle this, and we can just use
existing mechanisms that will make the playback core close and reopen
the AO. Whether the immediate reopening will actually succeeds really is
ALSA's problem, though.
We must not try to remap channels with this. Whethever ALSA gives us,
and whatever we do with it, the result will probably be nonsense.
Untested, as I don't have the required hardware.
This message is printed when the audio device advertised a channel map,
but couldn't set it - which is probably a dmix bug (we'll never know,
ALSA doesn't take bug reports).
Print the requested map, so that the user (maybe) can make a connection
when seeing the message and the actually used channel map, which might
be less confusing. Or at least less useless.
snd_pcm_prepare() was not always called, which could result in an
infinite loop.
Whether snd_pcm_prepare() was actually called depended on whether the
device was a hw device (or other characteristics; depending on
snd_pcm_hw_params_can_pause()), and required real suspend (annoying for
testing), so it was somewhat tricky to reproduce without knowing these
things.
When setting the ALSA channel map, we never actually set the map we got
from ALSA directly, but convert it to mpv's, and then back to ALSA's.
mpv and ALSA use different conventions for mono, and there is already an
exception for ALSA->mpv, but not mpv->ALSA.
This was only added recently (c1e97161) as an attempt to minimize the
bad impact of channel layout device aliases. But use of these was
removed in commit 49df0132. Now this code does pretty much nothing, and
shouldn't be needed anymore. It does something when using spdif, but
this fallback won't work anyway.
The "old" method (before the ALSA channel map API) used device aliases
like "surround51" to set the channel layout. The "interesting" part was
that these devices usually redirect to a hardware device. This means
playing stereo would lead you to the "default" device (dmix), while e.g.
5.1 to "surround51", which automatically takes care of the fact that
dmix can't do 5.1.
This is pretty much nonsense, though. It shouldn't depend on the damn
input media file whether the player is going to use shared access (dmix)
or exclusive access (direct hw device).
As a consequence, by default ao_alsa will do only what dmix can do. If
the user actually wants multichannel, he has to select a suitable hw
device with --audio-device. From there on, the correct speaker mapping
will be ensured via the channel mapping API.
The change is preparation for making multichannel output the default (as
far as supported by the audio output API). Of the common APIs, only ALSA
messes up beyond repair, so I feel like this change is needed.
On ancient alsa-lib versions, only stereo and mono can be played with
this branch.
dmix reports channel layouts it doesn't support. The rest of the
technical part of the story is in the code comment.
This seems to be the only reasonable way to fallback from trying to
initialize certain devices (like dmix) with multichannel audio. We could
probably add support for such padding channels to our audio chain or to
ao_alsa itself, but this would probably be much more work than this
commit.
What dmix does is probably a bug. I've tried to report it to ALSA. Thay
have a link on their website to a bug tracker, but it's a dead link, and
has been for years. I've posted to alsa-devel, but received no reply.
I'm thus assuming this absolutely retarded behavior is by design, and
nothing will happen to improve upon it.
I'm considering sending Lennart Poettering a "thank you" email, because
with PulseAudio, multichannel audio just works (although some other
things just don't work).
Whether we print it as warning or error doesn't really matter; we
continue anyway. (I don't actually know what the implications of running
in non-blocking mode are; for what's it worth, when I tested with
explicitly changing to non-blocking, it seemed to work fine anyway, so
don't change that part.)
ALSA returns "FL" as channel layout when trying to play mono. mpv and
libavresample don't like this; in particular, using libavresample to
convert stereo to "FL" fails.
If no-block was given, the device would be opened with SND_PCM_NOBLOCK.
Also, after opening, blocking mode was unconditionally enabled anyway
with snd_pcm_nonblock(). Further, if opening with SND_PCM_NOBLOCK
failed, opening was retried without this flag.
This doesn't make any sense to me, and I've never heard of someone using
this suboption. I suspect it has to do with ancient ALSA bugs or API
caveats. Remove it and simplify the code.
ALSA is crap. It's impossible to make multichannel playback just do the
right thing. dmix (the default on most distros) can do stereo only, and
will refuse to play multichannel. On the other hand, if you try like mpv
(and mplayer) to open a multichannel device (like "surround51" etc.),
this will actually open a hardware device, which will either fail if
dmix is active, or block out dmix if opening succeeds.
This commit falls back to "default" (i.e. dmix) if opening a
multichannel device fails, which is a tiny step towards the right
behavior. (Although fixing it fully is impossible.)
This could trigger an assertion when using ao_alsa or ao_coreaudio. The
code was simply assuming the number of channel maps was bounded
statically (which was true at first in both AOs).
Fix by using dynamic memory allocation. It needs to be explicitly
enabled by the AOs by setting a temp context, because otherwise the
memory couldn't be freed. (Or at least this seems to be the most elegant
solution.)
Fixes#1306.
This seems safer: otherwise, opening the AO could randomly fail if the
audio formats happens to be not float.
Unfortunately, this only works if the user does not select a device.
Since ALSA devices are arbitrary strings, including plugins with complex
parameters, it's not trivial or maybe even impossible to edit the string
in a way the "plug" plugin is added.
With --audio-device, it would be safe for users to select either
"default" or one of the "plughw" devices. Everything else seems
questionable.
Use the ALSA channel map API for querying and selecting supported
channel maps.
Since we (probably?) want to be compatible with ALSA versions before the
change, we still try to select the device name by channel map, and open
that device. There's no way to negotiate a channel map before opening,
so we're stuck with this approach. Fortunately, it seems these devices
allow selecting and setting any other supported channel layout, so maybe
this is not an issue at all. In particular, this avoids selecting the
default (dmix) device, which can only do stereo.
Most code is based on Martin Herkt <lachs0r@srsfckn.biz>'s alsa_ng
branch, with heavy modifications.
Don't crash if no fallback channel layout could be found (caller can't
handle NULL return from select_chmap()). Apparently this could never
actually happen, though.
Don't treat snd_pcm_hw_params_set_periods_near() failure as fatal error.
Same deal as with snd_pcm_hw_params_set_buffer_time_near().
Actually free channel maps returned by snd_pcm_get_chmap().
Adjust some messages.
No functional changes.
ALSA_PCM_NEW_HW_PARAMS_API was a pre-ALSA 1.0.0 thing and does nothing
with modern ALSA. It stopped being necessary about 10 years ago.
3 functions are moved to avoid forward references.
If ALSA reports a channel map, and it looks like it makes sense (i.e.
could be converted to mpv channel map, and the channel count matches),
then use that instead of the channel map we are assuming.
This is based on code written by lachs0r (alsa_ng branch).
Apparently this can "sometimes" return an error. In my opinion, this
should never return an error: neither the semantics of the function,
nor the ALSA documentation or ALSA sample code seem to indicate that
a failure is to be expected. I'm not perfectly sure about this though
(I blame ALSA being a weird, big, underdocumented API).
Since it causes problems for some users, and since there is really no
reason why we should abort on such an error, turn it into a warning.
Fixes#1231.
Unfortunately, ALSA is particularly bad with this, because mpv has to
add all sorts of magic crap to the device name to make things work. The
device selection overrides this, so explicitly selecting devices will
most likely break your audio. This has yet to be solved.
Before this commit, there was AF_FORMAT_AC3 (the original spdif format,
used for AC3 and DTS core), and AF_FORMAT_IEC61937 (used for AC3, DTS
and DTS-HD), which was handled as some sort of superset for
AF_FORMAT_AC3. There also was AF_FORMAT_MPEG2, which used
IEC61937-framing, but still was handled as something "separate".
Technically, all of them are pretty similar, but may use different
bitrates. Since digital passthrough pretends to be PCM (just with
special headers that wrap digital packets), this is easily detectable by
the higher samplerate or higher number of channels, so I don't know why
you'd need a separate "class" of sample formats (AF_FORMAT_AC3 vs.
AF_FORMAT_IEC61937) to distinguish them. Actually, this whole thing is
just a mess.
Simplify this by handling all these formats the same way.
AF_FORMAT_IS_IEC61937() now returns 1 for all spdif formats (even MP3).
All AOs just accept all spdif formats now - whether that works or not is
not really clear (seems inconsistent due to earlier attempts to make
DTS-HD work). But on the other hand, enabling spdif requires manual user
interaction, so it doesn't matter much if initialization fails in
slightly less graceful ways if it can't work at all.
At a later point, we will support passthrough with ao_pulse. It seems
the PulseAudio API wants to know the codec type (or maybe not - feeding
it DTS while telling it it's AC3 works), add separate formats for each
codecs. While this reminds of the earlier chaos, it's stricter, and most
code just uses AF_FORMAT_IS_IEC61937().
Also, modify AF_FORMAT_TYPE_MASK (renamed from AF_FORMAT_POINT_MASK) to
include special formats, so that it always describes the fundamental
sample format type. This also ensures valid AF formats are never 0 (this
was probably broken in one of the earlier commits from today).
Until now, the audio chain could handle both little endian and big
endian formats. This actually doesn't make much sense, since the audio
API and the HW will most likely prefer native formats. Or at the very
least, it should be trivial for audio drivers to do the byte swapping
themselves.
From now on, the audio chain contains native-endian formats only. All
AOs and some filters are adjusted. af_convertsignendian.c is now wrongly
named, but the filter name is adjusted. In some cases, the audio
infrastructure was reused on the demuxer side, but that is relatively
easy to rectify.
This is a quite intrusive and radical change. It's possible that it will
break some things (especially if they're obscure or not Linux), so watch
out for regressions. It's probably still better to do it the bulldozer
way, since slow transition and researching foreign platforms would take
a lot of time and effort.
wm4
Marcin Kurczewski
Kevin Mitchell