[mythtv] [patch] multi channel audio patch 1

Mark Spieth mark at dclabs.com.au
Fri Dec 30 04:04:04 EST 2005

attached is the next version of the multi channel audio patch.
I have tested it with ALSA and it works up to 6 channels with timestretch 
with a AC3.5.1 avi I have. I have only listened to 2 channels connected to 
my sound card though so this needs more testing. Ive limited it to 6 
channels at the moment.
AC3 passthrough support is not handled yet so you need to use all 3 jacks 
from your audio card to test currently. So dont use it yet (ac3 

however from my alsa reading you can get alsa to reencode te 6 channel audio 
back to AC3 but I dont know how this is done. If this is true, I may just 
leave it at that and not reencode in myth (easier for me :) ).
There is a bit of code for support of ac3 reencode in audio layer which I 
may back out if an ALSA setup is viable.

no mmx for soundtouch mods yet so it does take a bit of grunt. hopefully a 
sunday or monday job.

there is a VERBOSE flag added for my testing called timestamp. if you want 
use it with
I find it useful to remove timestamp generated logging but still have the 
important AUDIO and PLAYBACK messages come out.

to enable go to the audio setup screen in the frontend and select the 
appropriate number of channels.

I may start a ticket for the next rev to keep track of the devel a bit if 
thats ok.

so feedback is now required as I dont have the setup to test more than I 

no change to behaviour if in 2 channel max mode.


----- Original Message ----- 
From: Mark Spieth
To: Development of mythtv
Sent: Monday, December 19, 2005 9:06 AM
Subject: Re: [mythtv] [patch] multi channel audio patch 1

woops forgot the soundtouch mods. here it is again.
----- Original Message ----- 
From: Mark Spieth
To: mythtv-dev at mythtv.org
Sent: Sunday, December 18, 2005 11:00 PM
Subject: [mythtv] [patch] multi channel audio patch 1

here is my interim patch for multi track audio.
doesnt work with oss and 2.6.11+ kernels due to a bug in the driver.
havent tested with alsa yet as its not my main config.
the setting MaxChannels defaults to 2 if it doesnt exist int the settings 
table so you need to set it to make use of 6 channel audio.
timestretch should work for 1,2,4 and 6 channels but no MMX as yet and dont 
know how well. I may change the strategy if the results are not that good 
which I suspect.
ac3/dts passthru not yet coded but there is a place for it in 
if anyone feels lucky and would like to try it the feedback would be 
appreciated. hopefully I havent left out any files.
probably wont get back to it until next weekend.
any pointers to instantiating an AC3/DTS encoder would be appreciated.

mythtv-dev mailing list
mythtv-dev at mythtv.org

mythtv-dev mailing list
mythtv-dev at mythtv.org
-------------- next part --------------
A non-text attachment was scrubbed...
Name: mythtv_ac3.3.patch.bz2
Type: application/octet-stream
Size: 13483 bytes
Desc: not available
Url : http://mythtv.org/pipermail/mythtv-dev/attachments/20051230/092f20b7/mythtv_ac3.3.patch.obj

More information about the mythtv-dev mailing list