[FFmpeg-user] Why is audio sampling rate 22050 not supported for WebM ?

[Shyam Sundar]

Hi,

I just realized after upgrading FFmpeg from 2.2.1 to 2.8.1 recently that
22050 audio sample rate is no longer supported for WebM encoding by latest
FFmpeg versions.

Dumping output below, using sample video Wlidlife.wmv that comes in all
WIndows machines (C:\Users\Public\Videos\Sample Videos).

It used to work earlier. It is still working for other formats, seems to be
a problem only for webm. Any idea why is that so ? By design or a bug ?

Thanks

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C:\>ffmpeg.exe -i C:\Wildlife.wmv -ar 22050 C:\Output.webm

ffmpeg version 2.8.1 Copyright (c) 2000-2015 the FFmpeg developers
  built with gcc 5.2.0 (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-aacenc
--enable-libvo-amrwbenc
 --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp
--enabl
e-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-lzma
--ena
ble-decklink --enable-zlib
  libavutil      54. 31.100 / 54. 31.100
  libavcodec     56. 60.100 / 56. 60.100
  libavformat    56. 40.101 / 56. 40.101
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5. 40.101 /  5. 40.101
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  2.101 /  1.  2.101
  libpostproc    53.  3.100 / 53.  3.100
Guessed Channel Layout for  Input Stream #0.0 : stereo
Input #0, asf, from 'C:\Wildlife.wmv':
  Metadata:
    SfOriginalFPS   : 299700
    WMFSDKVersion   : 11.0.6001.7000
    WMFSDKNeeded    : 0.0.0.0000
    comment         : Footage: Small World Productions, Inc; Tourism New
Zealand
 | Producer: Gary F. Spradling | Music: Steve Ball
    title           : Wildlife in HD
    copyright       : -¬ 2008 Microsoft Corporation
    IsVBR           : 0
    DeviceConformanceTemplate: AP at L3
  Duration: 00:00:30.09, start: 0.000000, bitrate: 6977 kb/s
    Stream #0:0(eng): Audio: wmav2 (a[1][0][0] / 0x0161), 44100 Hz, 2
channels,
fltp, 192 kb/s
    Stream #0:1(eng): Video: vc1 (Advanced) (WVC1 / 0x31435657), yuv420p,
1280x7
20, 5942 kb/s, 29.97 fps, 29.97 tbr, 1k tbn, 1k tbc
[libvpx-vp9 @ 0000000004f68820] v1.4.0
[libopus @ 0000000004f69900] Specified sample rate 22050 is not supported

Output #0, webm, to 'C:\Output.webm':
  Metadata:
    SfOriginalFPS   : 299700
    WMFSDKVersion   : 11.0.6001.7000
    WMFSDKNeeded    : 0.0.0.0000
    comment         : Footage: Small World Productions, Inc; Tourism New
Zealand
 | Producer: Gary F. Spradling | Music: Steve Ball
    title           : Wildlife in HD
    copyright       : -¬ 2008 Microsoft Corporation
    IsVBR           : 0
    DeviceConformanceTemplate: AP at L3
    Stream #0:0(eng): Video: vp9 (libvpx-vp9), yuv420p, 1280x720, q=-1--1,
200 k
b/s, 29.97 fps, 29.97 tbn, 29.97 tbc
    Metadata:
      encoder         : Lavc56.60.100 libvpx-vp9
    Stream #0:1(eng): Audio: opus, 0 channels, 128 kb/s
    Metadata:
      encoder         : Lavc56.60.100 libopus
Stream mapping:
  Stream #0:1 -> #0:0 (vc1 (native) -> vp9 (libvpx-vp9))
  Stream #0:0 -> #0:1 (wmav2 (native) -> opus (libopus))
Error while opening encoder for output stream #0:1 - maybe incorrect
parameters
such as bit_rate, rate, width or height
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