Alex Bennee wrote:
Hi,
I've been working on a patch (FS#10160) to get some m4a files I own to
play on Rockbox. Originally it looked as though the problem was
Rpckbox's limitation on only being able to handle files with a single
"mdat" atom containing data for the codec. Some I dug into the code
and started adding support for this case.
As it happens although the test file in question has two "mdat" atoms
the second one is of zero length (probably a placeholder). However the
reason the file wasn't playing is because additional information
needed to start playback (in the "moov" atom) is after the main "mdat"
atom where rockbox used to stop parsing the file.
moov after mdat is not uncommon at all. Some MP4 writer SW do that so
they can 1st write all the data, then add the "header" at the end. Of
course that messes up streaming such files....
I could take this as a quick win, redefine the code to only deal with
single mdat's but parse the whole file before starting. However there
is nothing in the MP4 container spec that says files can't have
multiple "mdat" atoms. However I'm suffering a lack of good test cases
to work with.
Yes, in theory you could have each "sample" inside it's own mdat if you
wanted.
So do you have any mp4, m4a or other mp4-alike file that won't play
with the rockbox libm4a codec? If so could you send me a copy?
Even better would be if anyone could tell me the command line foo to
generate such a multi-chucked mp4 file so I can make my own test
cases.
there is the ffmpeg/mplayer samples database, maybe they have something.
(http://samples.mplayerhq.hu/)
