[FFmpeg-devel] Error in ATRAC1 decoder?

Michael Niedermayer michael at niedermayer.cc
Mon Nov 16 01:45:39 CET 2015

On Sat, Nov 14, 2015 at 02:59:30AM +0300, Даниил Чередник wrote:
> Hello!
> I have noticed if decode
> https://samples.ffmpeg.org/A-codecs/ATRAC1/Test%20tones%20disc%20-%20Chirp.aea
> file by ffmpeg we got aliasing near 11025Hz. Screenshots:
> https://yadi.sk/i/r-95jZkKkSnbu https://yadi.sk/i/PV92LNESkSnby
> I was tried to solve it:
> ATRAC1 - hybrid codec, has two stacked QMF and splits the signal into 3
> band before MDCT. Thereby we need to compensate delay of one QMF to
> achieve reconstruction.
> There is a delay line but it looks like delay for 23 sample is not correct.
> I have done some experiments and got 39 should be right delay. Results of
> decoding with patch: https://yadi.sk/i/yooaIQrmkSncB
> https://yadi.sk/i/CUXsH7-CkSncK

> To be honest I am not a prof in math and it would be great if someone
> recheck it from math perspective.

i dont think math can help here
whatever a format requires that has to be done, this could even be
wrong from a math point of view of a ideal transform

> There is a patch in attach.

the patch also affects the atrac1 fate test
have you checked if the new output for that test is better than the
old ?

make V=2 fate-atrac1

also have you looked at other files, is this improving all files ?
any that get worse ?


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Many that live deserve death. And some that die deserve life. Can you give
it to them? Then do not be too eager to deal out death in judgement. For
even the very wise cannot see all ends. -- Gandalf
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 181 bytes
Desc: Digital signature
URL: <http://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20151116/5e6b5048/attachment.sig>

More information about the ffmpeg-devel mailing list