The VideoLAN Forums

Posted: **19 Feb 2011 08:07**

Hello, it seems that VLC player cannot play back sound with MPEG-2 files containing a mono MP2 audio track, for example http://david.van-kemenade.net/MPEG-TS_w ... 256kbps.ts. VLCP 1.1.7 plays the video track fine, the audio track is muted. When I encode a similar file with a stereo MP2 256kbps, the sound is played back fine. The mono file that is problematic for VLCP plays back fine in Windows Media Player and (after authoring to VOB) hardware DVD players. Is this a bug?

Posted: **19 Feb 2011 10:17**

There is something strange going on with the audio track of this file, I'm not sure what it is. Being mono shouldn't be the problem though but even after demuxing the track I got no DirectShow player being able to play it, not even MPC-HC using its built-in filters.
VLC also fails at playing the demuxed track but MPlayer and FFplay are able to play properly both the original TS and the demuxed audio.
I have the feeling it might be a splitter issue.

Code: Select all

mpeg_audio debug: MPGA channels:1 samplerate:48000 bitrate:256
...
main debug: using audio output module "aout_directx"
main debug: TIMER module_need() : 16.000 ms - Total 16.000 ms / 1 intvls (Avg 16.000 ms)
main debug: output 'f32l' 48000 Hz Stereo/Mono frame=1 samples/8 bytes
main debug: mixer 'f32l' 48000 Hz Stereo/Mono frame=1 samples/8 bytes
main debug: no need for any filter
main debug: looking for audio mixer module: 3 candidates
main debug: using audio mixer module "float32_mixer"
main debug: TIMER module_need() : 0.000 ms - Total 0.000 ms / 1 intvls (Avg 0.000 ms)
main debug: input 'mpga' 48000 Hz Mono frame=1152 samples/1161 bytes
main debug: looking for audio filter module: 1 candidate
scaletempo debug: format: 48000 rate, 2 nch, 4 bps, fl32
scaletempo debug: params: 30 stride, 0.200 overlap, 14 search
scaletempo debug: 1.000 scale, 1440.000 stride_in, 1440 stride_out, 1152 standing, 288 overlap, 672 search, 2400 queue, fl32 mode
main debug: using audio filter module "scaletempo"
main debug: TIMER module_need() : 0.000 ms - Total 0.000 ms / 1 intvls (Avg 0.000 ms)
main debug: filter(s) 'mpga'->'f32l' 48000 Hz->48000 Hz Mono->Stereo/Mono
main debug: looking for audio filter module: 14 candidates
main debug: no audio filter module matching "any" could be loaded
main debug: TIMER module_need() : 0.000 ms - Total 0.000 ms / 1 intvls (Avg 0.000 ms)
main debug: looking for audio filter module: 14 candidates
mpgatofixed32 debug: mpga->f32l, bits per sample: 0
main debug: using audio filter module "mpgatofixed32"
main debug: TIMER module_need() : 0.000 ms - Total 0.000 ms / 1 intvls (Avg 0.000 ms)
main debug: looking for audio filter module: 14 candidates
main debug: using audio filter module "trivial_channel_mixer"
main debug: TIMER module_need() : 0.000 ms - Total 0.000 ms / 1 intvls (Avg 0.000 ms)
main debug: found 2 filters for the whole conversion
main debug: filter(s) 'f32l'->'f32l' 52800 Hz->48000 Hz Stereo/Mono->Stereo/Mono
main debug: looking for audio filter module: 14 candidates
bandlimited_resampler debug: f32l/52800KHz/2->f32l/48000KHz/2
main debug: using audio filter module "bandlimited_resampler"
main debug: TIMER module_need() : 0.000 ms - Total 0.000 ms / 1 intvls (Avg 0.000 ms)
main debug: found a filter for the whole conversion
main debug: End of audio preroll
main debug: Decoder buffering done in 8 ms
main warning: PTS is out of range (-10000), dropping buffer
main warning: PTS is out of range (-34000), dropping buffer
mpgatofixed32 debug: libmad error: bad bitrate/mode combination
mpgatofixed32 debug: libmad error: bad bitrate/mode combination
mpgatofixed32 debug: libmad error: bad bitrate/mode combination
mpgatofixed32 debug: libmad error: bad bitrate/mode combination

Posted: **21 Feb 2012 11:49**

Sorry for reviving an old thread, but I'm having exactly the same issue here (VLC v1.1.11):
The MPEGs have been created using MPlayer's 'mencoder' (version SVN-r31854-4.3.2).

The stereo-ones play fine, but the mono ones are mute

But not always...

ffplay (version N-36193-gf514695) plays the audio
ffdshow: when set to "libmad" they're mute - when using "libavcodec", audio is there.
VirtualDub (with ffchandler's MPEG2 plugin) throws the following error:
Error: invalid or out-of-spec data encountered
Avidemux is mute, but the video-playback also stutters (about every 50 frames it pauses for half a second). Video plays fine with stereo MP2 audio.
Windows Media Player plays the audio

I really assume that the files are not 100% okay, but still it would be interesting to know why this happens...

@Lotesdelere/davidvankemenade:
Which tool did you use to encode these files?

Posted: **22 Feb 2012 08:48**

[*]VirtualDub (with ffchandler's MPEG2 plugin) throws the following error:
Error: invalid or out-of-spec data encountered
[*]Avidemux is mute, but the video-playback also stutters (about every 50 frames it pauses for half a second). Video plays fine with stereo MP2 audio.
[*]Windows Media Player plays the audio[/list]
I really assume that the files are not 100% okay, but still it would be interesting to know why this happens...

We need a sample.

Posted: **23 Feb 2012 15:50**

Sorry for the delay...

Had to re-encode one which is safe to put on the web (avoiding rights-issues):
http://download.das-werkstatt.com/pb/mt ... s-mono.mpg

Posted: **23 Feb 2012 17:49**

Can you create a ticket about that?

Posted: **26 Feb 2012 23:46**

Created one. Here:
https://trac.videolan.org/vlc/ticket/6260

Posted: **27 Feb 2012 14:42**

Mono in > 192kbit/s is NOT conform to Mpeg-1 Layer-2 spec. Fix your encoder.

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MPEG-2 with mono MP2 256 kbps is mute

MPEG-2 with mono MP2 256 kbps is mute

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Re: MPEG-2 with mono MP2 256 kbps is mute

Re: MPEG-2 with mono MP2 256 kbps is mute

Re: MPEG-2 with mono MP2 256 kbps is mute