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

[FFmpeg]

#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 Kamedo2):

 Replying to [comment:318 klaussfreire]:
 > I did manage to find a few low-hanging-bugs in ANMR, but, and this is
 quaint, fixing them makes ANMR 10x slower.
 Is that
 {{{
 Assertion diff >= 0 && diff <= 120 failed at libavcodec/aacenc.c:399
 }}}
 ? Rare, but it happens on some tracks.
 libavcodec/aacenc.c
 {{{
 /**
  * Encode scalefactors.
  */
 static void encode_scale_factors(AVCodecContext *avctx, AACEncContext *s,
                                  SingleChannelElement *sce)
 {
     int off = sce->sf_idx[0], diff;
     int i, w;

     for (w = 0; w < sce->ics.num_windows; w += sce->ics.group_len[w]) {
         for (i = 0; i < sce->ics.max_sfb; i++) {
             if (!sce->zeroes[w*16 + i]) {
                 diff = sce->sf_idx[w*16 + i] - off + SCALE_DIFF_ZERO;
                 av_assert0(diff >= 0 && diff <= 120);
                 off = sce->sf_idx[w*16 + i];
                 put_bits(&s->pb, ff_aac_scalefactor_bits[diff],
 ff_aac_scalefactor_code[diff]);
             }
         }
     }
 }
 }}}

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Ticket URL: <https://trac.ffmpeg.org/ticket/2686#comment:320>
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