[mythtv-users] SBLive - OpticalSPDIF issues

[Michael T. Dean]

Andy O'Brien wrote:

>Following Jarod's guide, I got a box with firewire capture working.
>(SDTV output through an nvidia geforce 4 card).
>
>ALSA appeared to be working though I wanted to get SP/DIF working so
>my reciever could get the 5.1 output from HBO, or whatever. Folllowed
>the guide a little closer, and using the .asoundrc and a little
>plugNplay I was able to get digital audio for a moment (reciever is
>plugged  into optical output on the Live! Drive IR), but on some
>channels the playback appears too fast (chipmunk syndrome) and it
>stutters each second).
>  
>
Sounds like you're sending a 44.1kHz signal to an S/PDIF input that's 
expecting 48kHz (which pretty much all of them do).  Therefore, you just 
need to fix your .asoundrc to resample the 44.1kHz signal into a 48kHz.  
If you're using an .asoundrc like Jarod is ( 
http://www.wilsonet.com/mythtv/asoundrc.txt ), then you're probably 
specifying the wrong output.  I.e. using ALSA:spdif will not convert.  
Using ALSA:default (when uncommenting the appropriate lines at the top) 
or ALSA:digital or ALSA:mixed-digital will convert.

>...
>
>I tried logging in as root and running with the realtime option turned
>on, no change. Now this is on a channel like cartoon network, and if I
>switch to a program on HBO, 5.1 audio kicks in on my reciever and it
>play normally. (haven't tried seeking too much yet))
>  
>
More support for the theory of PCM with the wrong frequency, channels, 
or period_time being sent to the digital output...  Since you're 
received an MPEG with AC3 on HBO and swtiching to an MPEG with PCM (at 
what sounds like 44.1kHz) on Cartoon Network, the sound card is fighting 
with Myth to try to get more sound even before Myth thinks it should 
need it, so...

>So any suggestions? system is an AMD XP 2400/1gig ram a 40gig main
>drive and a old 6gig LVMed for future expansion. Could having the
>slower drive in there be a problem? I don't think so because I can get
>an HBO program to play back with no apparent playback problems.
>  
>
Shouldn't be a problem.

>I had an issue where If I switch channels from HBO to something like
>Cartoon Network, Myth crashes, but I think it was because I had XvMC
>enabled or something, seems to be better now, here's the output
>anyway, maybe someone can confirm?
>
Can't confirm, but the audio may actually have something to do with it.  
If you want XvMC, I recommend testing it again once you fix the sound 
issues.

Mike