[mythtv-users] Audio Channels and Setup
Johan
mythtv at vulturest.com
Sun May 13 04:06:48 UTC 2007
Hi all,
I am using ALSA and have the following setup:
- SB Audigy 4 (EMU10K1 alsa driver)
- a 5.1 speaker setup plugged into the three (green, black, orange)
jacks on the sound card
- an asound.conf which
1. plugs default pcm to surround51
2. has a separate ch51dup device defined which duplicates
FL to RL, FR to RR and mixes FL/FR in various amounts for
the center and LFE channels.
All of this works perfectly. The following applies:
1. Playing a 2channel stereo file through the default device I get
playback in FL and FR.
2. Playing a 5.1 file through the default device I get properly
software decoded AC3/DTS in all speakers (sounds nice).
3. Playing a 2channel stereo file through the ch51dup device I get
the mix as specified earlier in all channels.
4. Playing a 5.1 file through the ch51dup I lose whatever was
coming from RR/RL/LFE/center channels in favour of the FL/FR->all
mix (expected, sounds bad).
Obviously I can't use passthrough in myth because I don't have a
hardware decoder. My options are then as follows:
1. Set the audio device to default: 2ch audio stays in front
speakers, 5.1channel audio correctly plays in all speakers.
2. Set the audio device to ch51dup: 2ch audio plays in all
speakers 5.1channel audio plays badly in all speakers.
The ideal setup here would be if the recording/LiveTV/etc only has 2
channels of audio, play through the ch51dup device for duplicated all
speaker goodness, and if >2channels is detected, use the
surround51/default device.
Is there any way to achieve this in myth? Ideally it would be nice to
setup 3 audio devices: stereo device, multi-channel device, passthrough
device.
Browsing through the myth source it looks like this would be a bit of an
effort to implement as the passthrough device is selected based on the
codec id being CODEC_ID_AC3 or CODEC_ID_DTS instead of on the number of
channels in the audio - looks like lots of classes to touch.
So before I go and hack myself a solution in the code, I thought I'd try
here and see if anyone has any ideas.
Regards,
Johan.
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