Multi-language sound tracks interfere each other

[aviphil87]

Dear all,

I record HD TV and get a 1920x1080 50fps .ts file. I convert it to 1280x720 25fps .mp4 with 2.6.9 (last version that for me works perfect, even though I have the same problem with 2.6.10).

When I keep only one audio track (AAC Faac, i.e. French, or English), the sound on the .mp4 file is cristal clear.

When I want to keep two audio tracks (both AAC Faac, i.e. French plus English, or French plus German), when playing one audio track, the other track somehow interferes with it.

It is not diaphony as we had with tape recorders (when listening a track, the one next to it was slightly audible in the background).

It sounds like drops and clips in the audio. Same drops and clips are on both tracks at the same places. They last only for a second or two, at intervals. They do not exist in the original .ts file.

Perhaps I do something wrong. Any idea somebody?

Thank you,

[mean]

A sample clip  would help

[Jan Gruuthuse]

Are you re-encoding the audio tracks? Forgot down mix AC3 to stereo?
I never came across this in copy mode when using mpeg-ts with 4 tracks (arteHD): 2 german 2 french (1 ac3, 1 stereo).

[aviphil87]

Folks, thanks for your answers. But after quite a few other tests, I am embarrassed:

   - Jan, I may not understand. I do recode video (from .ts H264 1920x1080 50fps, to .mp4 1280x720 25fps). Then, leaving audio in Copy mode brings three error messages:
        - Unsupported - Only AAC, AC3 and mpegaudio supported for audio
        - Muxer - Cannot open
        - Failed - File ... was not saved correctly
Even though the audio in the original file was already AC3, and thus is supposed to satisfy the requirement of the first message, it does not. And so, I must recode audio. Can't see stereo option,

   - Mean, I realized in the meantime that those drops and clips happen at random, and not in every input file. You mention Arte, so far after recoding both video and audio from this channel I did not yet get the problem. On other channels, sometimes the recode works fine, sometimes it clips. Depends of the channel and the program. I could not establish a rule. Only thing I can say is that when I get the clips, if I recode again the same file, I get the same clips. I could of course send you samples, except that if the problem appears to happen without a rule, I may feel shy you invest your time on an infrequent problem.

[Jan Gruuthuse]

I you used mp4 muxer, try mp4v2 muxer in Output Format. Could be related AC3 track is E-AC3 instead of AC3.

[aviphil87]

Folks, to follow-up on this, in the meantime I went into many trials and conversions. I could determine audio clippings and drops appear with E-AC3 sources, -and- when I keep two or more audio tracks. When I keep only one audio track, no defect.

As you suggest I also tried 'MP4v2 Muxer'. But it transforms "frames per seconds" into "seconds per frame": on the TV, a frame is displayed still and heavily pixelized for a few seconds, then an other frame for a few seconds, etc..., while both audio tracks respectively play OK.

It plays with audio defects in VLC and Windows Media Player. You proposed I send you a sample of both the original and converted file for your review, I have a two-minute excerpt ready, where is it explained how I can send it.

Thank you for your support,

[mean]

could you try encoding one audio track in AAC and the other one  in something else ?
( even WAV) ?

[mean]

I've found the problem, fix is on its way

[mean]

fixed

[aviphil87]

Thanks for the fix. Even if it's late now, just FYI, in the meantime I had tried many audio input formats. Every time I did as you suggest it works fine. The audio is clear, all clippings and distorsions are gone. Thank you for your usual good advice, it saved me many conversions.