FFmpeg's MP4 is not AAC?

[Djard]

Oops! I meant "M4A" in the subject.

I installed the FFmpeg v2.2.2 library for Audacity v2.0.6 that allowed me to export a demuxed audio file as "M4A (AAC) Files (FFmpeg)." Then I tried to remux it in Avidemux but got the message, ""Unsupported. Only AAC & mpegaudio supported for audio."

So I renamed the file extension to *.aac, but Avidemux gave the same error message. So FFmpeg's statement that M4A and AAC are the same is incorrect, or am I missing something here?

[Detmek]

You can not just change extention from .m4a to .aac. Aac extention is used for AAC elementary stream while M4A is used for MP4 that contains only audio. Use mp4box, ffmpeg or YAMB to extract aac stream from m4a file.

[Djard]

Well, I installed MP4Box and MyMP4BoxGUI. Then I tried to load an M4A file that I created with Audacity that has the FFmpeg plugin, supposedly supporting AAC files. MyMPBoxGUI notifies me that I must "Add a video stream first."

So I am not able to "Use mp4box...to extract aac stream from m4a file" as it is incapable of performing such a task. Has anyone actually converted successfully an M4A file to a true AAC, or is this file format off limits to open source projects?

[Cornucopia]

Use QtPro. Not free, but cheap, and works well.

Scott

[_Al_]

What kind of container are you muxing into?

[Djard]

Until I can manage to get a better home theater system that has good attenuation of dynamic range, I'm manually reducing the often ridiculous extended dynamic range of Blu-ray movies by using the Normalizer, Leveler, EQ and/or Compress features in my audio studio. So far I have managed to make the audio acceptable. Often actors' voices are get so buried in music or ambient sound that they're virtually inaudible. Surely the engineers are smoking too much weed in Hollywood. LOL!

Recoding audio one time has always been acceptable to my ear. But having to recode AAC to M4A then back to AAC, so that it's compatible with video in an MP4 container has me hesitating. But then maybe I'm doing things the hard way. I'd like to be able to work with AAC files the same way as I do with AC3, MP3, etc. I'm wondering what is so special about AAC that so few--if any--open source apps support encoding it. Maybe it's a DRM thing, but then AC3 is available. Forgive me if I am missing the boat entirely.

[Detmek]

Well, I installed MP4Box and MyMP4BoxGUI. Then I tried to load an M4A file that I created with Audacity that has the FFmpeg plugin, supposedly supporting AAC files. MyMPBoxGUI notifies me that I must "Add a video stream first."

So I am not able to "Use mp4box...to extract aac stream from m4a file" as it is incapable of performing such a task. Has anyone actually converted successfully an M4A file to a true AAC, or is this file format off limits to open source projects?

First click on tab Demux and then load your m4a file. Though, MyMP4BoxGUI has a problem packing raw aac stream into mp4/m4a if you don't have video stream. YAMB is better for that job.

Open-source software works just fine with these formats. You just need to learn how to use it.

Also, extracting and packing AAC stream in/from MP4 container is lossless process. You don't need to recode/encode/transconde anything.

[_Al_]

or try to use command line:
mp4box.exe -add old.mp4#video -add new_audio.m4a#audio -new out.mp4
maybe even this is enough:
mp4box.exe -add old.mp4#video -add new_audio.m4a -new out.mp4

[Djard]

The command line option is too complex for me. But thanks for responding.

I was about to give up after reading the horror stories of YAMB--from the developers site--permanently removing Windows' Start menu (several posts below the download page). But then VideoHelp offers a version that does not mess with Windows' libraries. So I created a directory and extracted the files there. I was then able to open an M4A file that I created with Audacity and had YAMB render it as an AAC file in less than a second. Yay!

Thank you for your patience. I'm truly grateful.