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

FFmpeg trac at avcodec.org
Mon Mar 2 13:35:07 CET 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):

 I tracked it all the way to codebook_trellis_rate and
 encode_window_bands_info with short windows. When the optimum allocation
 spans more than SCALE_MAX_DIFF sf, anmr is carefull not to create
 allocations that result in deltas to be encoded greater than
 SCALE_MAX_DIFF, but codebook_trellis_rate and the other both undo this. I
 tried many ways to patch that with no avail as of yet. The issue almost
 always happens near zero bands and the switch from one window group to the
 next (which is usually where the greatest deltas happen and where it is
 hardest to enforce).

 But I did just notice the assertion error happens on git head as well. It
 seems like a pre-existing bug. Feel free to check exactly under which
 conditions, I just saw the error logs on a run of tests and didn't get to
 comparing when it happens vs v9b just yet.

Ticket URL: <https://trac.ffmpeg.org/ticket/2686#comment:364>
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