[mythtv-commits] Ticket #5962: Global audio offset/delay config to delay audio on playback for displays which add video lag

MythTV mythtv at cvs.mythtv.org
Thu Dec 4 05:08:19 UTC 2008

#5962: Global audio offset/delay config to delay audio on playback for displays
which add video lag
 Reporter:  grokky       |       Owner:  ijr    
     Type:  enhancement  |      Status:  new    
 Priority:  minor        |   Milestone:  unknown
Component:  mythtv       |     Version:  unknown
 Severity:  low          |     Mlocked:  0      
 With the increasing number of TV's performing significant image processing
 (ie, motionflow, de-blurring, etc), and such processing taking a finite
 time, this can result in audio being ahead of video. In some cases turning
 off extra processing in the TV can reduce this lag, but sometimes some of
 this processing is beneficial, even with mythtv.

 This most commonly occurs if audio is not being processed via the TV, ie,
 it is passthrough, or routed directly to a receiver/amplifier from the
 frontend, whilst video goes direct to the TV.

 As myth can do some of the processing work (such as upscaling) to provide
 a similar video stream to the TV, regardless of source, I suspect the
 processing delay added by any TV would be quite constant, regardless of
 source/quality/bitrate etc. Without myth (ie using the internal tuner of a
 digital 1080p TV), processing time could vary if it was tuned to a 1080p
 station, vs say a 720p or SD channel.

 As a result, it might be possible (and extremely useful to those people
 affected by this), to add a config item either globally, or by channel, to
 code in an audio offset to start all recordings,livetv or mythvideo
 playback with, which could then be further altered during playback if
 required (unlikely) by the usual mechanism.

 This would alleviate the need to dial in an offset each and every time
 playback is started.

 I would be happy to test any work done in this area, and we could start
 with just a DB config item, rather than GUI.

Ticket URL: <http://svn.mythtv.org/trac/ticket/5962>
MythTV <http://www.mythtv.org/>

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