[FFmpeg-trac] #7058(avcodec:new): loud aac encoder artefact (was: FLAC to AAC sound falls)

[FFmpeg]

#7058: loud aac encoder artefact
-------------------------------------+-------------------------------------
             Reporter:  nol2ter      |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  important    |                Component:  avcodec
              Version:  git-master   |               Resolution:
             Keywords:  aac          |               Blocked By:
  regression                         |  Reproduced by developer:  0
             Blocking:               |
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
Changes (by cehoyos):

 * keywords:   => aac regression
 * priority:  normal => important
 * version:  unspecified => git-master
 * component:  undetermined => avcodec


Comment:

 Strangest bug ever, thank you!

 I believe this is a regression since
 8005b6de4f88c9e3739a3a4ceda4288804788df9
 For the original command line, the bug depends on
 `strlen(LIBAVCODEC_IDENT)`, explaining why it was a regression since
 70143a3954e1c4412efb2bf1a3a818adea2d3abf fixed by
 36c85d6e773d51af1d084fb15ad89d9acc5dd893 but the issue is also
 reproducible without writing bitstream info:
 {{{
 $ ffmpeg -i 59s_sound_falls_original.flac -b:a 320k -flags +bitexact
 -aac_coder twoloop -t 65 out.aac
 ffmpeg version N-90232-g0645698 Copyright (c) 2000-2018 the FFmpeg
 developers
   built with gcc 6.3.0 (GCC)
   configuration: --enable-gpl
   libavutil      56.  8.100 / 56.  8.100
   libavcodec     58. 13.102 / 58. 13.102
   libavformat    58. 10.100 / 58. 10.100
   libavdevice    58.  2.100 / 58.  2.100
   libavfilter     7. 12.100 /  7. 12.100
   libswscale      5.  0.102 /  5.  0.102
   libswresample   3.  0.101 /  3.  0.101
   libpostproc    55.  0.100 / 55.  0.100
 Input #0, flac, from '59s_sound_falls_original.flac':
   Metadata:
     TITLE           : Clarity
     ARTIST          : Zedd, Foxes
     ALBUMTITLE      : Clarity
     COMMENT         : 00602537547067_1_5;0bfaa24dc0cb300acd9f604b3b5f261b
   Duration: 00:04:31.43, start: 0.000000, bitrate: 1046 kb/s
     Stream #0:0: Audio: flac, 44100 Hz, stereo, s16
 Stream mapping:
   Stream #0:0 -> #0:0 (flac (native) -> aac (native))
 Press [q] to stop, [?] for help
 [adts @ 0x27d3140] The AVFormatContext is not in set to bitexact mode,
 only the AVCodecContext. If this is not intended, set
 AVFormatContext.flags |= AVFMT_FLAG_BITEXACT.
 Output #0, adts, to 'out.aac':
   Metadata:
     TITLE           : Clarity
     ARTIST          : Zedd, Foxes
     ALBUMTITLE      : Clarity
     COMMENT         : 00602537547067_1_5;0bfaa24dc0cb300acd9f604b3b5f261b
     encoder         : Lavf58.10.100
     Stream #0:0: Audio: aac (LC), 44100 Hz, stereo, fltp (16 bit), 320
 kb/s
     Metadata:
       encoder         : Lavc aac
 size=    2534kB time=00:01:05.01 bitrate= 319.3kbits/s speed=19.4x
 video:0kB audio:2515kB subtitle:0kB other streams:0kB global headers:0kB
 muxing overhead: 0.761414%
 [aac @ 0x27d42c0] Qavg: 9635.397
 }}}
 The output file contains a very audible artefact after 59 seconds.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/7058#comment:3>
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