[mythtv-commits] Ticket #4819: Faint audio from 5.1 upmix on MPEG-4 files

MythTV mythtv at cvs.mythtv.org
Mon Mar 3 04:52:54 UTC 2008


#4819: Faint audio from 5.1 upmix on MPEG-4 files
-------------------------------------------+--------------------------------
 Reporter:  Yeechang Lee <ylee at pobox.com>  |       Owner:  ijr    
     Type:  defect                         |      Status:  new    
 Priority:  minor                          |   Milestone:  unknown
Component:  mythtv                         |     Version:  head   
 Severity:  medium                         |     Mlocked:  0      
-------------------------------------------+--------------------------------
 I am running r16254, and have noticed this issue since the multichannel
 audio support in #1104 was committed to trunk. Relevant ./configure flags
 are --enable-libx264, --enable-libmp3lame, --enable-libfaad, --enable-
 libfaac, --enable-libfftw3.

 My frontend outputs audio via S/PDIF. I have AC3 and DTS passthrough
 enabled. My Myth recordings are all originally in MPEG-2 (via OTA or
 FireWire); many have AC3 tracks. Some recordings have since been converted
 by mythtranscode into MPEG-4, which also downmixed any AC3 tracks into
 stereo. I also play via MythVideo various AVI files in both Xvid and Divx
 formats with either AC3 or MP3 audio.

 If I set Max Audio Channels to 5.1 and Upmix to either Active Linear or
 Active Simple, here is what I get audiowise with various video/audio
 combinations, with no timestretch used:

  * MPEG-2/AC3: No problem.
  * MPEG-2/non-AC3: No problem.
  * MPEG-4/non-AC3: Audio is so faint it's almost inaudible.
  * Xvid/MP3: Audio is so faint it's almost inaudible.
  * Divx/AC3: No problem.

 The audio problems go away if I either set Max Audio Channels to Stereo,
 or keep Max Audio Channels at 5.1 but set Upmix to Passive.

 Brad Dermanouelian [http://www.gossamer-
 threads.com/lists/mythtv/users/319415#319415 reports the same issue] with
 his analog card-captured MPEG-4 MythTV recordings.

-- 
Ticket URL: <http://svn.mythtv.org/trac/ticket/4819>
MythTV <http://svn.mythtv.org/trac>
MythTV


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