Author Topic: AviDemux cannot handle MP4 files with LPCM audio  (Read 139 times)

HenrikRClausen

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AviDemux cannot handle MP4 files with LPCM audio
« on: September 26, 2017, 11:31:40 AM »
My Sony HandyCam AX-53 (compact 4K camera) outputs MP4 files with LPCM audio (192 kbit/s). While they play just fine in various media players, AviDemux cannot decode the audio correctly. The length of audio is interpreted as just half that of the video (16 seconds video is shown to have 8 seconds of audio). Audio playback is choppy (video is fine), and whenever I compress to another format (MP4, MKV), the audio is saved as it sounds, making it impossible to filter/recompress files from my HandyCam.

Now, I understand that using LPCM in .MP4 files may be a violation of the specs for MP4, but that's not really a solution. Being able to decode files with this flaw would be the solution.

Anyone else having this problem? Solutions..?

mean

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Re: AviDemux cannot handle MP4 files with LPCM audio
« Reply #1 on: September 26, 2017, 12:13:45 PM »
You tried with 2.7.0 right ?

xtro

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Re: AviDemux cannot handle MP4 files with LPCM audio
« Reply #2 on: October 19, 2017, 01:27:02 PM »
Perhaps it is due to how the audio is resampled or decoded. A common problem using cam as source,  and perhaps a frames per second issue due to whatever speed the video plays at causing decoding issues in avidemux eg 29.9 NTSC fps? I would extract the raw audio and convert to your preferred audio output using any free audio converter out there, then remux it back into your source mp4 video. Have a look at the synch, but don't worry if it is out of synch too much.

 Later run it through avi demux(keeping the same video speed!) but just copying the 'fixed' audio to edit your video or whatever you intended to get good synch as it recodes anew.  If not recode both the video and this new audio(not copy) together at your preferred bitrates and with a view to recoding the video and its audio to 23.96fps if it isn't already and doing a 3:2 pulldown if necessary?
« Last Edit: October 19, 2017, 01:34:41 PM by xtro »