[mythtv-commits] Ticket #3471: nuvexport - wrong audio bitrate with ffmpeg

[MythTV]

#3471: nuvexport - wrong audio bitrate with ffmpeg
------------------------------+---------------------------------------------
 Reporter:  anonymous         |       Owner:  xris   
     Type:  defect            |      Status:  new    
 Priority:  minor             |   Milestone:  unknown
Component:  perl / nuvexport  |     Version:  unknown
 Severity:  low               |  
------------------------------+---------------------------------------------
 When i use nuvexport with ffmpeg for Xvid export, nuvexport produces Xvid
 files that seem incorrect (for approx. 2 months). These files can be
 played with no error with mplayer, but if i try to play them with a
 hardware player (based on EM8511 chip, such as Tvix), the sound is broken,
 fastforward is impossible, and the player can hang. I don't think this is
 a bug of the harware player, because, file information on the generated
 files (by a 'ffmpeg -i') gives the following:
 {{{
   Duration: 00:41:15.3, start: 0.000000, bitrate: 1471 kb/s
   Stream #0.0: Video: mpeg4, yuv420p, 640x480, 25.00 fps(r)
   Stream #0.1: Audio: mp3, 48000 Hz, stereo, 0 kb/s
 }}}
 Did you notice the last line : Audio 0 kb/s?

 ffmpeg has recently changed some command line arguments (I use ffmpeg
 20070329 on Debian Testing). According to the ffmpeg's doc and examples
 ([http://ffmpeg.mplayerhq.hu/ffmpeg-doc.html#SEC5] (...) -ab 128k (...)),
 the '-ab' (audio bitrate) flag must be followed by a bitrate and a 'k' (or
 another unit, of course), whereas nuvexport does not use this 'k'.
 export/ffmpeg/XviD.pm contains, line 182 (SVN version):
 {{{
      .' -ab '.$self->{'a_bitrate'}
 }}}
 If i add a simple 'k' like this:
 {{{
      .' -ab '.$self->{'a_bitrate'}.'k'
 }}}
 generated Xvid files are Ok, and 'ffmpeg -i' gives the following info:
 {{{
   Duration: 00:41:15.3, start: 0.000000, bitrate: 1439 kb/s
   Stream #0.0: Video: mpeg4, yuv420p, 640x480, 25.00 fps(r)
   Stream #0.1: Audio: mp3, 48000 Hz, stereo, 96 kb/s
 }}}
 There is no more '0 kb/s' and the file works perfectly on my player. Note
 that the '-ab' flag is used in each file in 'export/ffmpeg', so the
 problem can arise with other formats.

 Perhaps this bug could explain some other problems with nuvexport/ffmpeg
 such as [http://www.gossamer-threads.com/lists/mythtv/users/243009]
 (nuvexport - drastic quality difference)?

 I suppose this change does not work with old versions of ffmpeg (before
 March/April 07?). I know that nuvexport checks the ffmpeg version
 (export/ffmpeg.pm, line 70) but since I don't know which version
 introduces new command-line arguments, I don't know how to use version
 checking (and I must admit my knowledge of Perl is very limited!).

 Hope this will help.

 David.

-- 
Ticket URL: <http://svn.mythtv.org/trac/ticket/3471>
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