[mythtv-commits] Ticket #6569: ac3 level is low for 5.1 source

MythTV mythtv at cvs.mythtv.org
Mon Jun 8 06:09:14 UTC 2009

#6569: ac3 level is low for 5.1 source
 Reporter:  markspieth               |        Owner:  ijr    
     Type:  patch                    |       Status:  new    
 Priority:  minor                    |    Milestone:  unknown
Component:  MythTV - Video Playback  |      Version:  unknown
 Severity:  medium                   |   Resolution:         
  Mlocked:  0                        |  

Comment(by markspieth):

 finally had time to look into this again.
 the problem I had experienced was my stupid error.
 I'd made some different mods to my main frontend which didnt reflect the
 algo correctly.

 The patch does work correctly for both 6ch output and 2ch downmixed output
 for both 2.0 and 5.1 ac3 source material.

 I suspect there is a gain problem that is scaled for the number of
 channels in the source. thus 1/3 (-10dB) for 6ch over 2ch. (2ch being
 louder). This is not a downmix issue either.

 The spec does not mention this though. The gain values in the table should
 probably be 3 and not 3.16 for this reason.

 If anyone has mixed 4ch/2ch or 4ch/6ch audio material it would be
 interesting to test this theory. I only have access to mixed 2ch/6ch

Ticket URL: <http://svn.mythtv.org/trac/ticket/6569#comment:4>
MythTV <http://www.mythtv.org/>

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