adpcm_swf: 11khz mode decodes as 5khz

[ami_stuff]

I don't know if this is a bug in ffmpeg or in encoding software.

C:\>ffmpeg -i 11khz_mono_44kbps.flv out.wav
ffmpeg version N-78410-g588e2e3 Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 5.3.0 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-av
isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enab
le-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --
enable-libdcadec --enable-libfreetype --enable-libgme --enable-libgsm --enable-l
ibilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enab
le-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --en
able-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --ena
ble-libtwolame --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --
enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-lib
x265 --enable-libxavs --enable-libxvid --enable-libzimg --enable-lzma --enable-d
ecklink --enable-zlib
  libavutil      55. 17.100 / 55. 17.100
  libavcodec     57. 24.102 / 57. 24.102
  libavformat    57. 25.100 / 57. 25.100
  libavdevice    57.  0.101 / 57.  0.101
  libavfilter     6. 31.100 /  6. 31.100
  libswscale      4.  0.100 /  4.  0.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
Input #0, flv, from '11khz_mono_44kbps.flv':
  Metadata:
    creationdate    : Thu Feb 25 04:13:06 2016
    Encoded_With    : Sorenson Squeeze
    Encoded_By      :
  Duration: 00:00:02.43, start: 0.000000, bitrate: 183 kb/s
    Stream #0:0: Audio: adpcm_swf, 5512 Hz, mono, s16, 22 kb/s
Output #0, wav, to 'out.wav':
  Metadata:
    creationdate    : Thu Feb 25 04:13:06 2016
    Encoded_With    : Sorenson Squeeze
    ITCH            :
    ISFT            : Lavf57.25.100
    Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 5512 Hz, mono, s16, 8
8 kb/s
    Metadata:
      encoder         : Lavc57.24.102 pcm_s16le
Stream mapping:
  Stream #0:0 -> #0:0 (adpcm_swf (native) -> pcm_s16le (native))
Press [q] to stop, [?] for help
size=     208kB time=00:00:09.74 bitrate= 175.0kbits/s speed=N/A
video:0kB audio:208kB subtitle:0kB other streams:0kB global headers:0kB muxing o
verhead: 0.036584%

[Carl Eugen Hoyos]

Looks like an encoder bug, see page six of ​https://www.adobe.com/content/dam/Adobe/en/devnet/flv/pdfs/video_file_format_spec_v10.pdf
Could you try to encode mono, stereo of 5kHz, 11kHz, 22kHz and 44kHz audio?
(or playback with Adobe software...)

[Carl Eugen Hoyos]

The code is there for some time already: 6ed08157cad67b9b2c2e0cb90fe4af082df04919

[Carl Eugen Hoyos]

What happens if you encode long audio (like an hour) with a working sample rate: Does the length change? I wonder because the specification states 44kHz but we use 44100.

[ami_stuff]

Here are the other samples which decodes correctly:

​http://www.datafilehost.com/d/1fc368a4