Please auto-adjust high bitrates in AC3 encoder

[Max Brustkern]

I'm running the following command:
/usr/bin/ffmpeg -i ./data/sound-file.wav ~/test.ac3
On Oneiric, it works correctly, and outputs this:
ffmpeg version 0.7.3-4:0.7.3-0ubuntu0.11.10.1, Copyright (c) 2000-2011 the Libav developers
  built on Jan 4 2012 16:08:51 with gcc 4.6.1
  configuration: --extra-version='4:0.7.3-0ubuntu0.11.10.1' --arch=amd64 --prefix=/usr --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-libvpx --enable-runtime-cpudetect --enable-vaapi --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --enable-shared --disable-static
  libavutil 51. 7. 0 / 51. 7. 0
  libavcodec 53. 6. 0 / 53. 6. 0
  libavformat 53. 3. 0 / 53. 3. 0
  libavdevice 53. 0. 0 / 53. 0. 0
  libavfilter 2. 4. 0 / 2. 4. 0
  libswscale 2. 0. 0 / 2. 0. 0
  libpostproc 52. 0. 0 / 52. 0. 0
Input #0, wav, from './data/sound-file.wav':
  Duration: 00:00:00.76, bitrate: 706 kb/s
    Stream #0.0: Audio: pcm_s16le, 44100 Hz, 1 channels, s16, 705 kb/s
Unable to find a suitable output format for '/home/ubuntu/test.ace'
ubuntu@server-4541:/opt/canonical.com/qa-regression-testing/scripts$ /usr/bin/ffmpeg -i ./data/sound-file.wav ~/test.ac3
ffmpeg version 0.7.3-4:0.7.3-0ubuntu0.11.10.1, Copyright (c) 2000-2011 the Libav developers
  built on Jan 4 2012 16:08:51 with gcc 4.6.1
  configuration: --extra-version='4:0.7.3-0ubuntu0.11.10.1' --arch=amd64 --prefix=/usr --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-libvpx --enable-runtime-cpudetect --enable-vaapi --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --enable-shared --disable-static
  libavutil 51. 7. 0 / 51. 7. 0
  libavcodec 53. 6. 0 / 53. 6. 0
  libavformat 53. 3. 0 / 53. 3. 0
  libavdevice 53. 0. 0 / 53. 0. 0
  libavfilter 2. 4. 0 / 2. 4. 0
  libswscale 2. 0. 0 / 2. 0. 0
  libpostproc 52. 0. 0 / 52. 0. 0
Input #0, wav, from './data/sound-file.wav':
  Duration: 00:00:00.76, bitrate: 706 kb/s
    Stream #0.0: Audio: pcm_s16le, 44100 Hz, 1 channels, s16, 705 kb/s
Incompatible sample format 's16' for codec 'ac3', auto-selecting format 'flt'
[ac3 @ 0x1d56d80] channel_layout not specified
[ac3 @ 0x1d56d80] No channel layout specified. The encoder will guess the layout, but it might be incorrect.
Output #0, ac3, to '/home/ubuntu/test.ac3':
  Metadata:
    encoder : Lavf53.3.0
    Stream #0.0: Audio: ac3, 44100 Hz, mono, flt, 64 kb/s
Stream mapping:
  Stream #0.0 -> #0.0
Press ctrl-c to stop encoding
size= 6kB time=0.77 bitrate= 64.0kbits/s
video:0kB audio:6kB global headers:0kB muxing overhead 0.000000%

On the most recent package in Precise, it fails, and outputs this:
ffmpeg version 0.8-4:0.8-1ubuntu1, Copyright (c) 2000-2011 the Libav developers
  built on Jan 24 2012 07:15:53 with gcc 4.6.2
This program is not developed anymore and is only provided for compatibility. Use avconv instead (see Changelog for the list of incompatible changes).
Input #0, wav, from './data/sound-file.wav':
  Duration: 00:00:00.76, bitrate: 706 kb/s
    Stream #0.0: Audio: pcm_s16le, 44100 Hz, 1 channels, s16, 705 kb/s
Incompatible sample format 's16' for codec 'ac3', auto-selecting format 'flt'
[ac3 @ 0x12a65e0] channel_layout not specified
[ac3 @ 0x12a65e0] No channel layout specified. The encoder will guess the layout, but it might be incorrect.
[ac3 @ 0x12a65e0] invalid bit rate
Output #0, ac3, to '/home/ubuntu/test.ac3':
    Stream #0.0: Audio: ac3, 44100 Hz, mono, flt, 200 kb/s
Stream mapping:
  Stream #0.0 -> #0.0
Error while opening encoder for output stream #0.0 - maybe incorrect parameters such as bit_rate, rate, width or height

I know it previously worked on Precise, but I don't have a version number for the last time I verified that it worked. The input file is attached. Working version on Oneiric is 4:0.7.3-0ubuntu0.11.10.1. Failing version on precise is 4:0.8-1ubuntu1.

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: ffmpeg 4:0.7.3-0ubuntu0.11.10.1
ProcVersionSignature: Ubuntu 3.0.0-15.26-generic 3.0.13
Uname: Linux 3.0.0-15-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 1.23-0ubuntu4
Architecture: amd64
CheckboxSubmission: 45e465ddf7959aab9a61cdadad3b8cd9
CheckboxSystem: 4ed15c40009aa6f7770f606350a390a2
Date: Wed Feb 8 17:29:54 2012
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1)
ProcEnviron:
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: libav
UpgradeStatus: Upgraded to oneiric on 2011-10-13 (118 days ago)

[Reinhard Tartler (siretart)]

On Mi, Feb 08, 2012 at 23:35:44 (CET), Max Brustkern wrote:

> Public bug reported:
>
> I'm running the following command:
> /usr/bin/ffmpeg -i ./data/sound-file.wav ~/test.ac3

In precise, please try using 'avconv' instead of 'ffmpeg'.

Moreover, does using "-acodec ac3_fixed" work better in this case? I
notice in your output that you are using the float-based ac3 encoder,
and there are some warning messages in the output.

--
Gruesse/greetings,
Reinhard Tartler, KeyID 945348A4

[Max Brustkern (nuclearbob)]

Tried this command line instead:
/usr/bin/avconv -i /opt/canonical.com/qa-regression-testing/data/sound-file.wav -acodec ac3_fixed test.ac3
Got similar output:
avconv version 0.8-4:0.8-1ubuntu1, Copyright (c) 2000-2011 the Libav developers
  built on Jan 24 2012 07:15:53 with gcc 4.6.2
Input #0, wav, from '/opt/canonical.com/qa-regression-testing/data/sound-file.wav':
  Duration: 00:00:00.76, bitrate: 706 kb/s
    Stream #0.0: Audio: pcm_s16le, 44100 Hz, 1 channels, s16, 705 kb/s
[ac3_fixed @ 0x169b600] channel_layout not specified
[ac3_fixed @ 0x169b600] No channel layout specified. The encoder will guess the layout, but it might be incorrect.
[ac3_fixed @ 0x169b600] invalid bit rate
Output #0, ac3, to 'test.ac3':
    Stream #0.0: Audio: ac3, 44100 Hz, mono, s16, 200 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (pcm_s16le -> ac3_fixed)
Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height

Also tried -acodec=ac3, and without -acodec specified, and all 3 with ffmpeg instead of avconv, and all cases failed.

[Justin Ruggles (justin-ruggles)]

There is no such thing as 200kbps AC-3. We need to modify the AC-3 encoder to choose the closest bit rate. 192k should work.

[Reinhard Tartler (siretart)]

@justin: Thanks for the comment, much appreciated.

the AC-3 encoder could at least give better error messages. Auto adjusting bitrate would be also great.