AC3 in Australia (Was Re: [mythtv] DVB 3.4 report)

[Mark Anderson]

For those that are interested, attached is a patch that allows AC3 audio to 
work in Australia. All previous problems outlined in this thread have been 
resolved, some via dirty hacks.

The stuttering I was experiencing was caused by the hack to mpeg.c. The 
changes in mpeg.c treat all PRIVATE_STREAM_1 packets as AC3 audio with no 
header (0x80), which appears to be what oz stations are transmitting. 
However, transform.c doesn't realise this and was occasionally finding 
PRIVATE_STREAM_1  packets that had 0x80 or 0x20 as the first byte and adding 
an extra header to them, which created an invalid AC3 packet for the hacked 
mpeg.c and resulting in the stutter. I have hacked transform.c to not put the 
extra headers on which fixes the stutter problem. This of course is not a 
workable solution in the long term since the hack will only work in aus 
presumably. Maybe someone who knows more about mpeg.c and transform.c can 
look at this and see if they can work it out?

The rest of the changes should be useful to everyone, including the new GUI 
option to enable AC3 audio and the audio re-initialisation code when the 
audio codec changes.

Note, I have only tried this with AC3 to SPDIF, i.e. not software AC3.

Cheers,
Mark Anderson
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