VLC 1.1.12 regression with 5.1 audio and PulseAudio

[floomp]

Since upgrading to 1.1.12, I noticed that the 5.1 audio (3F2R/LFE) in my MKV files is being incorrectly converted to stereo. The balance is off, and sounds and voices are louder in the right or left channel. This doesn't happen with Totem, mplayer, or VLC 1.1.11. I wasn't able to totally disable PulseAudio to test it, but if I switch VLC to the OSS audio module, then run "padsp vlc", the audio is fine, so I'm assuming it's a problem with VLC's PulseAudio module. (Well, until it starts crashing, which is fixed if I switch the module to default then back to OSS, but I don't think that's related.)

I'd prefer to use 1.1.12 since it fixes the audio sync issue with PA, but I have a lot of videos with 5.1 audio, so this is kind of annoying. Should I attach a debug log?

[Rémi Denis-Courmont]

It depends what you expect... I don't recall any change to the channel mapping code between 1.1.11 and 1.1.12 though.

[floomp]

Well, I did some git bisecting, and narrowed it down to git commit 5b24e072c971c5984ba29a16f029e36f13b3d5d1. Unfortunately, I don't understand the code, but hopefully knowing the commit is helpful?

I'm running PulseAudio 1.0. The audio is fine with regular stereo audio files (AVIs in my case), only 5.1 has the problem.

[Rémi Denis-Courmont]

It looks like a bug in PulseAudio itself then, though it's hard to say without the VLC and PulseAudio debug logs...

[floomp]

Here's the PulseAudio debug log (only what was written while VLC was running). Might be relevant:

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D: [pulseaudio] resampler.c: Channel matrix: D: [pulseaudio] resampler.c: I00 I01 I02 I03 I04 I05 D: [pulseaudio] resampler.c: +------------------------------------ D: [pulseaudio] resampler.c: O00 | 0.675 0.100 0.188 0.000 0.000 0.188 D: [pulseaudio] resampler.c: O01 | 0.000 0.000 0.188 0.675 0.100 0.188 I: [pulseaudio] remap.c: Using generic matrix remapping

And the VLC debug log (only for a few seconds of playback, verbosity level 2). Possibly relevant:

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a52 debug: A/52 channels:2 samplerate:48000 bitrate:384000 main debug: creating aout main debug: looking for audio output module: 4 candidates pulse debug: using stereo channel map

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pulse debug: connected to device alsa_output.pci-0000_00_1b.0.analog-stereo (0) pulse debug: digital pass-through not available pulse debug: using buffer metrics: maxlength=4194304, tlength=15552, prebuf=0, minreq=7680

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pulse debug: using surround-51 channel map pulse debug: connected to device alsa_output.pci-0000_00_1b.0.analog-stereo (0) pulse debug: digital pass-through not available pulse debug: using buffer metrics: maxlength=4194312, tlength=46656, prebuf=0, minreq=23040

(I guess it connected twice?)

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main debug: output 'f32l' 48000 Hz 3F2R/LFE frame=1 samples/24 bytes main debug: mixer 'f32l' 48000 Hz 3F2R/LFE frame=1 samples/24 bytes

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main debug: TIMER module_need() : 0.155 ms - Total 0.155 ms / 1 intvls (Avg 0.155 ms) main debug: filter(s) 'a52 '->'f32l' 48000 Hz->48000 Hz 3F2R/LFE->3F2R/LFE

Thanks for your time. Hope this helps.

[Rémi Denis-Courmont]

Since you played cut&paste, it's hard to say for sure, but it looks like you were first playing the stereo track, then changed to the 5.1 track and it's being sent as 5.1 to PulseAudio. That would seem perfectly normal if you have a DVD with both stereo and surround tracks. So I don't see any bug there.

[floomp]

Since you played cut&paste, it's hard to say for sure,

Ah, sorry, the unaltered files were ~150KB each, and I didn't think that much was necessary. I can upload the full logs if needed though (assuming that's what you meant).

but it looks like you were first playing the stereo track, then changed to the 5.1 track and it's being sent as 5.1 to PulseAudio. That would seem perfectly normal if you have a DVD with both stereo and surround tracks. So I don't see any bug there.

Well, there definitely isn't any input from me during this. I can tell VLC to open a file directly, and the problem immediately appears the moment it starts playing. Anything that happened in the debug log was done automatically by VLC - I didn't do anything else apart from telling it to open the file. Additionally, the file itself only has 1 audio track (5.1), no separate stereo track.

If the 5.1 track is being sent as 5.1 to PulseAudio like it should, then it's either being sent from VLC incorrectly, or PulseAudio is interpreting it incorrectly.

Update: I've written a patch. It looks like the channel map is not being sent to PulseAudio at all with the new method. After reading the PA API documentation for a bit, I came up with this:

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diff --git a/modules/audio_output/pulse.c b/modules/audio_output/pulse.c index 8f48bf2..8b3fde8 100644 --- a/modules/audio_output/pulse.c +++ b/modules/audio_output/pulse.c @@ -837,6 +837,7 @@ static int Open(vlc_object_t *obj) formatv[formatc]->encoding = encoding; pa_format_info_set_rate(formatv[formatc], ss.rate); pa_format_info_set_channels(formatv[formatc], ss.channels); + pa_format_info_set_channel_map(formatv[formatc], &map); formatc++; } @@ -846,6 +847,7 @@ static int Open(vlc_object_t *obj) pa_format_info_set_sample_format(formatv[formatc], ss.format); pa_format_info_set_rate(formatv[formatc], ss.rate); pa_format_info_set_channels(formatv[formatc], ss.channels); + pa_format_info_set_channel_map(formatv[formatc], &map); formatc++; /* Create a playback stream */

This solves the problem, and it seems like the correct way.

[amaury.dg]

Same problem here on opensuse 12.1.

[Rémi Denis-Courmont]

Same problem because OpenSUSE packagers don't actually follow vlc-1.1.git and take important fixes, contrary to Ubuntu or Debian.

[amaury.dg]

My VLC package comes from download.videolan.org....So I don't think it's Opensuse packagers fault.

[Rémi Denis-Courmont]

Then build from the HEAD of vlc-1.1.git, not from the 1.1.12 tarball. There probably won't be further formal releases in the 1.1.0 stable branch from now on.