Change channel configuration inside MP4-container

[FLX90]

Hello,

I want to change channel configuration of an ALAC audio stream inside MP4-container without multiplexing the container.

So I need to change letter H of Audio Data Transport Stream with a hex editor for all audio frames.
https://wiki.multimedia.cx/index.php/ADTS#Header

I installed AAC Audio ED Viewer to know where I should look at in my hex editor. Because the viewer can only handle AAC streams and I thought ALAC should look similar:


[Attachment 71308 - Click to enlarge]

But when I open my AAC reference stream inside the MP4-container I even cannot find the audio frames in the hex editor I see in the viewer:


[Attachment 71309 - Click to enlarge]

I can find many syncwords (0xFFF) inside media data container (mdat). But they don't match those I can see in the viewer.

Attachments:

• AAC sample file (© WARNER BROS.)
• ALAC sample file (© WARNER BROS.)

Can someone tell me what I'm doing wrong here?

Best
Felix

[FLX90]

If you want to freely change the channel configuration of the audio stream, you can try the ViWizard Audio Converter. Some specific formats of music files are not widely supported, so you may occasionally encounter errors that do not recognize them. If you have multiple audio from Apple Music, iTunes, and Audible, the ViWizard audio converter can convert them to popular formats such as MP3, M4A, AAC, FLAC, WAV, and M4B. It also allows you to customize output audio settings, such as sampling rate, bit rate, codec, channel, volume, speed, and tone.

This will mess up metadata.

Solution: https://stackoverflow.com/a/76419487/4928433

Audio isn't playable.
But that's another story ...