Extracting HE-AAC from MP4 and muxing with MP4 or MKV

[adoniscik]

The HE-AAC encoded MP4 file plays fine.
The extracted HE-AAC plays fine in WinAMP
The remuxed MP4 or MKV plays with pops.


I have tested the following tools for remuxing:

AviMux 1.16.5 (not forgetting the "SBR" option)
mp4UI 1.0RC1


The decoder is CoreAAC 1.0b9

[bond]

try remuxing the .aac to .mp4 with mp4creator (for example via the ivan & menno gui as described in the audio faq)

[GrEEk_OuTcAsT]

Try to make the mkv avi with mkvtoolnix. The last version supports mp4.

[adoniscik]

I just tried mp4box and mp4creator60 and they also have the same problem. I did a little test. I took my Nero encoded mp4 file, extracted the HE-AAC audio, and created a new mp4 file. Every tool thinks the AAC file in the new mp4 file is LC, not HE. It is as if the extraction operation is dropping some information.

Surely I am not the first person to notice this! I have the most recent version of Nero. I will now look for HE-AAC files online to see whether Nero is the culprit.

[adoniscik]

mkvtoolnix did work! I found it very interesting that when I tried to use the MKV generated by it (with two HE-AAC streams), and tried to add subtitles using AviMUX, I had the same "popping". That means something is wrong with AviMUX. I did not have the patience to test mp4creator too.

[alexnoe]

Please change auto-lacing to ebml-lacing when muxing aac audio. Xiph-lacing (which is sometimes used when auto-lacing is enabled) is b0rked with aac-audio in 1.16.5.

However, i don't see why it only occurs when adding subtitles

[bond]

Originally posted by adoniscik
Every tool thinks the AAC file in the new mp4 file is LC, not HE. It is as if the extraction operation is dropping some informationindeed, use search to find out why extracting he-aac to .aac is a bad idea

[Stux]

Originally posted by adoniscik

The HE-AAC encoded MP4 file plays fine.
The extracted HE-AAC plays fine in WinAMP
The remuxed MP4 or MKV plays with pops.


I have tested the following tools for remuxing:

AviMux 1.16.5 (not forgetting the "SBR" option)
mp4UI 1.0RC1


The decoder is CoreAAC 1.0b9

Use the 3ivx Muxer for remuxing

[adoniscik]

indeed, use search to find out why extracting he-aac to .aac is a bad idea
I do not have an interest in extracting an AAC file, but no utility except mkvtoolnix currently supports MP4 so I am forced to do it if I want multiple HE-AAC streams. I hope people add MP4 support to their utilities in due time.
Please change auto-lacing to ebml-lacing when muxing aac audio. Xiph-lacing (which is sometimes used when auto-lacing is enabled) is b0rked with aac-audio in 1.16.5.
Let me clarify my remark; it does not only occur with subtitles. I conducted an experiment, generating two MKV files. The first solely with AviMUX. The sound was messed up. The second with mkvtoolnix, using AviMUX to add subtitles to the MKV file--just to see what it would do with the HE-AAC streams. Again, the sound was messed up. This proves that, at least with the default settings, AviMUX 1.16.5 can not handle HE-AAC. I will try the settings you suggested next time.

[alexnoe]

It can handle He-AAC. The bug is in the lacing. If you use any other audio format that allows frame sizes of k*255 bytes, it will not work either with xiph or auto lacing.