[mythtv-users] AC3 2/5.1 channel and normal wave audio recordings all working with timestretch?

[Debabrata Banerjee]

Does anyone have this configuration working? A code change sometime last 
year broke this (patch which is apparently trying to re-encode AC3 audio 
after timestretch). I either have a unique configuration or no one else is 
trying to what I am doing. It would seem bizarre that no one else is doing 
this on my hardware.

Setup:
F10 (same behavior as FC6 which I had run on last year)
EMU10K1 with livedrive -> toslink spdif connection to receiver.
default output alsa: default will output PCM wave audio over toslink which 
the receiver plays back
passthrough output: alsa:iec958 will output AC3 audio over toslink which the 
receiver will decode, 2 channel and 5.1 channel works fine.

This works fine for playing back HDTV streams with AC3 audio, as well as 
normal analog tv wave audio. Timestretch used to work as the spdif 
passthrough was disabled and AC3 audio was decoded to stereo before being 
timestretched.

When timestretch is enabled on an AC3 source, what happens is the 
"passthrough" device is disabled, and the AC3 encoder is enabled, which is 
clearly wrong. I can hack around this issue by setting the default device to 
alsa:iec958, which will make 2-channel AC3 work properly as the 2 channel 
AC3 is decoded, timestretched, re-encoded to 2-channel AC3, and output over 
toslink. OK assume other people's hardware works differently as somehow the 
default audio device can also be used for spdif output??? Regardless - 
switching to a AC3 5.1 file, we appear to follow the same chain, however the 
output stays fixed at 2-channel AC3, which may be ok, but the audio is 
clearly garbled, doesn't look like the encoder and or libsoundtouch knows 
what to do with the extra channels it got. I don't see how this can work for 
anyone else because it's not dependent my hardware.

I can't seem to easily fix this in the code as the parameters are stuck in 
abstraction hell, the passthrough disable does different things at different 
layers and it's not clear how to fix it. Also I assume the AC3 encoder would 
also work properly for 5.1 channels if it got the correct stream parameters?

Thanks,
Debabrata