[FFmpeg-trac] #2686(avcodec:open): Native AAC encoder collapses at high bitrates on some samples

FFmpeg trac at avcodec.org
Tue Mar 31 20:38:11 CEST 2015

#2686: Native AAC encoder collapses at high bitrates on some samples
             Reporter:  Kamedo2      |                    Owner:
                 Type:  defect       |  klaussfreire
             Priority:  normal       |                   Status:  open
              Version:  git-master   |                Component:  avcodec
             Keywords:  aac          |               Resolution:
  regression                         |               Blocked By:
             Blocking:               |  Reproduced by developer:  1
Analyzed by developer:  0            |

Comment (by klaussfreire):

 Sorry for the late reply. I meant to answer a while ago but other duties
 made me lose track.

 Currently, I'm debugging the patch adding support for 7350hz sample rates
 which doesn't pass the test for MIPS. So I'm debugging that, and am a bit
 at a loss. The issue seems to be a floating point precision issue that is
 ''not'' on the MIPS-specific side of the code, and that surfaces with
 hardware floating point emulation. So... doesn't look immediately fixable.

 So if I don't find a fix, the TODO follows:
  - Push small fixes
    * ANMR bugs
  - Push improvements (in no particular order)
    * M/S search improvements
    * Clip avoidance
    * VBR support
    * R/C improvements, bit allocation improvments, etc (this last step I'm
 not sure I can split in smaller steps, as they all interact and extracting
 one not only is difficult but may also cause regressions)

 The assertion error I will leave for GSoC students to try and fix (or will
 attack it later if GSoC fails to address it).

Ticket URL: <https://trac.ffmpeg.org/ticket/2686#comment:372>
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