[FFmpeg-trac] #5334(avcodec:open): support atrac lossless

FFmpeg trac at avcodec.org
Mon Nov 26 17:41:31 EET 2018

#5334: support atrac lossless
             Reporter:  ami_stuff    |                    Owner:
                 Type:  enhancement  |                   Status:  open
             Priority:  wish         |                Component:  avcodec
              Version:  git-master   |               Resolution:
             Keywords:  atrac3       |               Blocked By:
             Blocking:               |  Reproduced by developer:  1
Analyzed by developer:  0            |

Comment (by Maximumspatium):

 Atrac lossless appears to be abandoned today.

 As author of both Atrac3 and Atrac3plus implementations in ffmpeg, I think
 it should be possible to provide a quick support for decoding of the base
 layer which is simply either Atrac3 or Atrac3plus.

 The lossless property is achieved by the so-called '''enhancement layer'''
 (that's how Sony guys calls the residual data). It transmits differences
 between the original signal and its lossy encoding using
 Atrac3/Atrac3plus. I believe that due to the nature of the residual
 consisting of very small differences, some kind of entropy encoding is
 employed. Understanding it will be probably rather easy compared with the
 sophisticated lossy algorithms used in the base layer.

 Can someone provide me with samples, preferably those that use both Atrac3
 and Atrac3plus base layers as well as different bitrates? All datafilehost
 links attached to this issue are broken.

 Maxim Poliakovski

Ticket URL: <https://trac.ffmpeg.org/ticket/5334#comment:12>
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