• Status Closed
  • Percent Complete
  • Task Type Patches
  • Category Recording
  • Assigned To No-one
  • Operating System SW-codec
  • Severity Low
  • Priority Very Low
  • Reported Version Daily build (which?)
  • Due in Version Undecided
  • Due Date Undecided
  • Votes
  • Private
Attached to Project: Rockbox
Opened by ahellmann - 2008-05-18
Last edited by preglow - 2008-06-16

FS#9007 - MP3 encoder (codec & plugin) quality improvements

This patch gives better quality than the current due to the following changes:
(1) bugfix in bit allocation (correct sign for '1' values)
(2) increase range of mdct freq values (improves quality for single frequency peaks, dc-offset)
(3) bugfix in the encoding of 'big' frequency peaks (avoid misencoding of remaining data) did not happen without (2)
(4) make use of scale factors (reduces mp3 noise)
(5) unifications of mp3 encoder plugin and codec
(6) preserve integer scale factors for mdct calculation, small performance tweak
(7) separate mdct sign and absolute values, keep performance
The overall performance has slightely decreased.

Closed by  preglow
2008-06-16 08:00
Reason for closing:  Accepted

Looks good to me. If the performance decrease isn't too big (I haven't tested the patch myself yet), and it works better than before, go ahead and commit it. Now all we need is a transcoder plugin so we can get rid of the separate plugin version of this :>

MikeS commented on 2008-05-27 02:10

Surprisingly, it's really not all that demanding to run as is in SVN - 35% boost on Coldfire IIRC. My memory is very vague though on MP3/WV boost ratios since it's been so long.

Also, some adjustment of the bitrates available might be a good idea if this changes things since they were selected based on listening tests so that at least recording a single voice was quite intelligible for a particular channel count.

This task can be closed, because the patch is in SVN since r17679, 2008-06-02.


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