MPG input: Audio channel missing

[CryGuy]

Hi,

the file below (2,5 MB, 5 seconds) contains one video and two audio tracks (mp2 and ac3). Why is the AC3 track missing if opened in AviDemux? This can also be a problem of the file, not of AviDemux, but I don't know. Other tools like MkvMerge also doesn't recognize the AC3 track, whereas MPC-HC does see it.

http://www.file-upload.net/download-11342056/test.mpg.html

Thanks

[Jan Gruuthuse]

mpeg-ps, vlc reports 45 streams. So very strange video, don't know what to think of it.

[CryGuy]

Hi Jan,

thanks for replying. I've recorded a .TS file via DVB-S and remuxed it using FFmpeg. The original file contained 8 streams: 1x Video, 2x Audio, 5x others (including subtitle). I've picked only the video and audio streams when remuxing (no reencoding, just direct stream copy). This is what FFmpeg says about the resulting .mpg file:

Code Select Expand

    Stream #0:0[0x1c0]: Audio: mp2, 48000 Hz, stereo, s16p, 192 kb/s
    Stream #0:1[0x80]: Audio: ac3, 48000 Hz, stereo, fltp, 384 kb/s
    Stream #0:2[0x1e0]: Video: mpeg2video (Main), yuv420p(tv), 720x576 [SAR 64:45 DAR 16:9], max. 15000 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc


No other streams detected. But you're right regarding VLC. (Here it detects 27 streams, but I do not have the latest VLC build right now.)
So, now I don't know who's wrong or right. FFmpeg, VLC, AviDemux?

If of interest:
Original .TS file (truncated to the first 4 MB): http://tinyurl.com/gp5zq9z
My discussion about this issue in the FFmpeg forum: http://ffmpeg.org/pipermail/ffmpeg-user/2016-February/030952.html

[Jan Gruuthuse]

Still not understanding what you try to achieve?
- Understanding input.ts is orignal recording (source video)
- Load recorded .ts into avidemux. As you can see, once loaded avidemux detects the 2 audio tracks. (1st screen shot)
- You can name these: Menu -> Audio -> Select Track. (2nd screen shot)
- you can:
-- edit video
-- convert to other coding
-- use other container: mkv, mp4, ...

click on images to enlarge:

[CryGuy]

Still not understanding what you try to achieve?

As I wrote: I've remuxed input.ts to output.mpg using ffmpeg. If I open output.mpg inside avidemux, it doesn't see the contained ac3 channel. I was asking why. That's all.

[Jan Gruuthuse]

If you are re-muxing  with avidemux the 2 audio tracks are there, stereo and ac3.

[CryGuy]

I'm not using AviDemux for remuxing. My question was why the AC3 track is not found even though MPC-HC does find it. Thanks.

[AQUAR]

Maybe the muxing mode for the AC3 provides a hint.
VLC shows many audio tracks but none except the first actually produces sound.
Mediainfo shows the track but its ID doesn't seem to be defined.

[Jan Gruuthuse]

I'm not using AviDemux for remuxing. My question was why the AC3 track is not found even though MPC-HC does find it. Thanks.

The re-muxing was/is flawed, either due to ffmpeg or user interaction with ffmpeg.
Has nothing to do with avidemux.
- The original shows up correctly with two audio tracks.
- The avidemux remuxed shows up correctly with two audio tracks.
Avidemux is not a media player and should not be used as such.

[mean]

Avidemux will "find" the audio track if the two following conditions are met :
1- The audio track is advertised
2- Avidemux can find "enough" of usable data for it

On the original sample, plenty of audio tracks are advertised but few are usable
On the 2nd sample, i did not have time to check that both tracks are usable

[CryGuy]

I've changed the remuxing process. It seems it was not MPEG-2 but MPEG-1 before. Now the tracks are found correctly by AviDemux. (As FFmpeg derives the container format from the destination file extension (.mpg) if you don't force a specific format, I didn't expect this nowadays, and from the file extension itself I can not derive the container format.)

Asking a question does not mean blaming anyone. I'm just trying to narrow down the problem. I did not report a bug in AviDemux. As a developer myself, I would have double-checked this before (at least). Jan, I don't expect AviDemux being a media player.

Thanks guys!

[Jan Gruuthuse]

>8 >8 Why is the AC3 track missing if opened in AviDemux? This can also be a problem of the file, not of AviDemux, but I don't know. Other tools like MkvMerge also doesn't recognize the AC3 track, whereas MPC-HC does see it. >8 >8

As none developer, I'm not laying the blame anywhere.
- With the provided information provided we try to figure out what is going on.
- By testing the file(s) with avidemux and other programs  a reason was provided:

The re-muxing was/is flawed, either due to ffmpeg or user interaction with ffmpeg.

With that info you found out what was going on:

(As FFmpeg derives the container format from the destination file extension (.mpg) if you don't force a specific format, I didn't expect this nowadays, and from the file extension itself I can not derive the container format.)

Best Regards,
Jan

[CryGuy]

Jan, I don't know what you want to clarify. Everythings's fine IMO.