[PATCH] Output AAC as M4A for iTunes with metadata tags

[Jon Davies]

On 31 March 2011 23:42, richard <richard at richsim900.plus.com> wrote:
[...]
> That is what EasyTag seemed to suggest. The bitrates becomes weird.
>
> @ Jon
> Is ffmpeg-current aac -> m4a the patched or unpatched version of ffmpeg?

it's the patched version.  There appears to be something broken in the
way ffmpeg packages mpeg4 files, and if we can establish a test case
then there's half a chance of getting it fixed.

I did some digging into the libraries that things use:
- ffmpeg has its own libav libraries, it's libavformat that produces
the mpeg4 files
- MP4Box, which I had thought produced compliant mpeg4 files, actually
uses libavformat as well, so any bug in ffmpeg will probably be there
in MP4Box too
- EasyTAG uses the libmp4v2 library, part of the mpeg4ip project,
which mp4info is part of as well (which is what I was using to compare
m4a files from different packagers).
- AtomicParsley appears to use its own library

Of all the things that have been tried it boils down to three libraries:
- libavformat - known to be broken for Marantz CD Players
- libmp4v2 - believed to work
- AtomicParsley - not sure

Unless someone else gets there before me, I'll have a look at the
differences between what libavformat and libmp4v2 produce and see if I
can work what's broken.

I would be interested to know if an ffmpeg-generated m4a with all
(well, most of) the metadata stripped out works or not, it might help
narrow down what's breaking things - try AtomicParsley file.m4a
--metaEnema

Jon