[FFmpeg-devel] Error in ATRAC1 decoder?

[Даниил Чередник]

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.

There is a patch in attach.

Best Regards,

-- 
Daniil Cherednik
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