September 19, 2020, 02:53:32 am



Problem with LPCM audio from Sony FDR-AX53 video camera

Started by Kiel, September 14, 2016, 11:08:20 pm

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Avidemux 2.6.13 plays the audio track to fast and with interruptions (Windows 7 and Windows 10).

Here is a short sample file (filmed from the PC screen):!AnlM-zzX3IMVgQKqNy12DnBCgkrZ

Windows Media player and Handbrake don't have problems to play the audio track correct.

Does anyone have an idea how Avidemux could handle the file correct?


Quote from: Kiel on September 14, 2016, 11:08:20 pm
Here is a short sample file (filmed from the PC screen):!AnlM-zzX3IMVgQKqNy12DnBCgkrZ

Actually, PCM in MP4 is illegal, but the main problem seems to be the big endian format (pcm_s16be) of the audio. Once converted to pcm_s16le (and preferably remuxed as MKV), Avidemux plays gladly the resulting LPCM_audio_test-le.mkv:

ffmpeg -i LPCM_audio_test.mp4 -c:v copy -c:a pcm_s16le LPCM_audio_test-le.mkv


Thank you very much for your info.
With the above ffmeg command I can convert the files so that Avidemux can handle it.
It would be nice if Avidemux could process the files sometime directly.


Quote from: eumagga0x2a on September 14, 2016, 11:42:01 pm
ffmpeg -i LPCM_audio_test.mp4 -c:v copy -c:a pcm_s16le LPCM_audio_test-le.mkv

Kiel, I'm a bit rusty with batch files, but if you need to fix a lot of MP4s and do it from within Windows Explorer, I suggest you create a batch file, place it on your desktop and drag-and-drop 1 or more MP4s on to this icon.

@echo off
set filename=""

for %%F in (%1) do (
set filename=%%F
echo ffmpeg -i %%F -c:v copy -c:a pcm_s16le %%~nF.mkv 
        if errorlevel 1 goto ERROR_OCCURRED
if not "%1"=="" goto FILES_LOOP

echo An error occured when trying to process %filename%
echo Aborting...


At the moment the "echo" in "echo ffmpeg -i %%F -c:v copy -c:a pcm_s16le %%~nF.mkv" will just show you the command line that would be executed, but not actually run FFMPEG. So if you drop 3 MP4s on to the CONVERT.BAT icon you should see 3 command lines.  To activate it, remove this particular ECHO and re-save the batch file.

BTW, if FFMPEG is not in your path list, you can hardwire its full path into the batch file. To get the full path of a file in Windows Explorer, rather than just r.clicking on FFMPEG, instead on it. This will show an extra option: "Copy as path".



Thank you dosdan - the batch file is also a good idea that can help me.


It would be interesting to know if Avidemux not handling big-endian PCM audio is a conscious design decision or sort of a bug?

Pretty amazing batch scripting and great sense of understatement  :)



Quote from: mean on September 19, 2016, 04:11:55 am
In mov/mp4, "twos" is normally LPCM

Sure, but are Sony breaking the specs using MP4 instead of MOV container here, aren't they? Still, when remuxed as a true QuickTime video (or Matroska), Avidemux struggles with the big-endian LPCM audio like "twos".

(I don't want to imply that this should have any priority for 2.6.15 or later, just being curious)


I did a quick check, there is no obvious way to know if it is big or little endian
In mov/mp4 it should be big