[mythtv-users] SPDIF, Stutter and Query for where to look for more help

[Jeff Wormsley]

I found out why my SPDIF wasn't working on my D865GBF (duh, bad cable), 
but now am running into other problems. 

No matter what buffering I use (I've tried all four combinations of the 
two different audio buffering settings - why there are two and what the 
difference is I don't know, but one is in General and the other in 
Playback) I am getting audio buffering issues, which is causing the 
video output to stutter.  At least I am fairly certain that is the 
problem, as xine does the same thing, and with  --verbose=99 on the 
command line, it has a very similar "extending video to stay in sync 
with audio (paraphrase)" that myth puts out when using -v playback.  I 
am thinking that the root problem may be in the sample rate.  When I got 
the SPDIF working and send sound to it, my Sony receiver always says it 
is in PCM 48K mode.  I don't believe my recordings are in that bitrate 
(I know what I feed xine from mythvideo isn't, but I am not sure about 
the 6200 firewire capture), and this may be what is causing the pauses.  
At least, it would seem to make logical sense if I fed in data at a rate 
that matched 44.1K, and the sound card shoved it out at 48K, the card 
would then be starved for data.  (Or perhaps it is the other way 
around???)  I think the solution is somewhere in the .asoundrc as I have 
found examples of bitrate conversion, but I can't find any examples of 
one for my Intel board (all the ones I have seen have had specific 
tweaks for boards with nforce or SiS chipsets, which makes me think they 
would not be appropriate for my Intel board).  So, here are my questions:

1. Does the above make any sense, or am I completely off base?

2. If this could explain my stutters, and the .asoundrc file is the 
place to fix it, where should I turn for help?

3. (Mostly OT, but I'm sure others uses xine in mythvideo) In xine, I 
had to go to Expert mode and change the the mono and stereo audio 
settings from default to spdif to get playback when called from 
mythvideo, but there were several other settings for various 
multichannel modes.  Where does one find info on that?  Are they alsa 
things, or xine things?  I tried to use xine's help, but apparently that 
isn't installed by the RPM, as it told me it couldn't find the help 
files (installed from Axel's RPMs stable branch).  I ask, because I plan 
to rip my DVD's, and would like to keep the multichannel audio.

Thanks in advance,
  Jeff.

P.S. I suppose there are four other possibilities for stutter.  One, I 
used Jarod's guide suggestion to make mythfrontend run as root, but for 
some reason mythfrontend still says I need to SUID as root for smoother 
playback.  Two, my video sync is still USleep, as I can't run 7174 (see 
previous post about "split-screen" effect) and can't get OpenGL to run 
on 6629 (crashes X when I run glxgears).  Three, related to two, I also 
tried setting the permissions on /dev/rtc but mythfrontend still says I 
don't have permission.  Four, I am running a 3.0 P4 with 1G 800Mhz dual 
channel ram, which I am led to believe is fast enough for 1920x1080i 
decoding, but perhaps it really isn't.  Still, xine behaving just like 
myth makes me think that it is the audio that is the root cause, based 
on the verbose output of both.