[mythtv] AC3 DVB Patch 4 - Automatic audio codec selection

Mark Anderson markjanderson at mail.com
Tue Jan 25 22:20:32 EST 2005


Problem addressed by this patch:

DVB channels often have multiple audio track types, MPEG, AC3 (and various 
languages). By default mythtv will select and initialise iteself to the first 
audio track it finds. When you change between DVB channels with different 
audio track types, mythtv will only play the audio if it is the same type as 
the audio it was initalised with. 

The fix:

1. Added an option to the Configuration menu to enable and disable the 
selection of AC3 tracks. For frontends that support AC3 then this can be 
enabled and myth will select the AC3 track in preferrence to other tracks. If 
the option is disabled then myth will not select AC3 audio tracks.

3. Enhanced avformatdecoder to re-initalise the audio parameters when it 
encounters a change in audio codec (currently it is only re-initialised on a 
change in rate or channels which is not enough.)

4. dvbrecorder selects AC3 audio tracks in preference to MPEG if the AC3 
option is enabled. This piece will not be needed once PS recording is 
enhanced to recoord all audio tracks. 

After applying Patches 1 to 4, mythtv will support AC3 audio for DVB TS 
recordings. However, for PS recordings there is an additional hack patch that 
is needed to work around the fact that PS recordings only record a single 
audio track. I will post this patch shortly.
 
Cheers,
Mark Anderson
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