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a question from a a total non-expert in video/audio editing.

I have an MKV file (let's call it X) which contains an AC3 file which has some constant and unnecessary (for me) comments for visually impaired persons.

I have extracted the AC3 stream from X but am totally unfamiliar with AC3 stream internals and was wondering if there would be a way to easily filter out these comments from the AC3 stream? My personal guess is 'no', as I suspect the comments and the 'real' audio payload have already been muxed to respective AC3 channels but in the off-chance that I am wrong....

I've been able to extract AAC stream from another lo-fi MKV (let's call that one Y) and add it to X and this approach works but I am unsatisfied with the quality of that particular AAC and would like to use the AC3 without having to search for yet another, separate MKV (let's call that one Z) which contains the proper AC3 which I would then include into X.

I guess there is also the possiblity of suppressing the audio altogether from X's AC3 with an appropriate band-pass filter and leaving voice-only from AAC stream with another band-pass filter and then combining the two but that seems like an awful, complicated, clunky and forced solution which is really a last-resort measure (it's probably easier to just find another MKV and download it).

Any thoughts/suggestions are greatly appreciated.

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  • What does MediaInfo or similar tool show for the various streams from the MKV? It's possible that the commentary is in a separate stream which you can eliminate by copying all the others using ffmpeg or similar – Jim Mack Mar 22 '14 at 19:34
  • There are three streams only - each for respective language. I do not see separate commentary stream. – quantum Mar 22 '14 at 20:07
  • Then it seems like the commentary was mixed down into the main audio, which makes it nearly impossible to separate. I hope someone else has a suggestion, but I wouldn't expect much. – Jim Mack Mar 23 '14 at 2:52
  • Indeed - as I suggested above, it could conceivably be done but it would be a mountain of effort - as far as I can see it, at least. I was hoping AC3 was keeping such streams separate and has algorithms which mix it in on-the-fly based on user selection (it would more efficient that way)....however, thinking about it, that may have been a long shot. Thanks for your comments. – quantum Mar 23 '14 at 15:10

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