[mythtv-users] SBLive - OpticalSPDIF issues

Andy O'Brien andyob at gmail.com
Sun May 15 01:00:25 UTC 2005


Hey Michael, thanks for the responce, sorry I haven't had much time to
fiddle with the box lately, but after checking all my settings I still
haven't figured out what's going on here.

Attached is my .asoundrc file, let me know if you think this is the
problem or if it's something else. I tried ALSA:default, ALSA:spdif,
ALSA:digital, and ALSA:mixed-digital, the default/digital settings do
what I describe below, Stuttering Chipmonk on lower channels like
Cartoon Network, and no problems with HBO.

Thanks again for the initial responce...
Andy

pcm.!default {
  type plug
## Uncomment the following to use mixed analog by default
#  slave.pcm "dmix-analog"
## Uncomment the following to use unmixed digital by default
  slave.pcm "digital-hw"
## Uncomment the following to use mixed digital by default
#  slave.pcm "dmix-digital"
}

# Alias for analog output on the Audigy (hw:0,0)
# - This is identical to the device named "default"--which
# always exists and refers to hw:0,0 (unless overridden)
# - Therefore, we can specify "hw:0,0", "default", or "analog"
# to access analog output on the Audigy
pcm.analog {
 type plug
 slave.pcm "analog-hw"
}

# Control device (mixer, etc.) for the Audigy card
ctl.analog {
 type hw
 card 0
}

# Alias for (rate-converted) mixed analog output on the
# Audigy (hw:0,0)
#  - This will accept audio input--regardless of rate--and
# convert to the rate required for the dmix plugin
# (in this case 48000Hz)
pcm.mixed-analog {
 type plug
 slave.pcm "dmix-analog"
}

# Control device (mixer, etc.) for the Audigy card
ctl.mixed-analog {
 type hw
 card 0
}

# Alias for (rate-converted) digital (S/PDIF) output on the
# Audigy (hw:0,0)
#  - This will accept audio input--regardless of rate--and
# convert to the rate required for the S/PDIF hardware
# (in this case 48000Hz)
pcm.digital {
 type plug
 slave.pcm "digital-hw"
}

# Control device (mixer, etc.) for the Audigy card
ctl.digital {
 type hw
 card 0
}

# Alias for mixed (rate-converted) digital (S/PDIF) output on the
# Audigy (hw:0,0)
#  - This will accept audio input--regardless of rate--and
# convert to the rate required for the S/PDIF hardware
# (in this case 48000Hz)
pcm.mixed-digital {
 type plug
 slave.pcm "dmix-digital"
}

# Control device (mixer, etc.) for the Audigy card
ctl.mixed-digital {
 type hw
 card 0
}

# The following devices are not useful by themselves.  They
# require specific rates, channels, and formats.  Therefore,
# you probably do not want to use them directly.  Instead use
# of of the devices defined above.

# Alias for analog output on the Audigy (hw:0,0)
# (AOB: Changed to hw:0,2 on a hunch)
# Do not use this directly--it requires specific rate,
# channels, and format
pcm.analog-hw {
 type hw
 card 0
 device 0
 # The default value for device is 0, so no need to specify
}

# Control device (mixer, etc.) for the Audigy card
ctl.analog-hw {
 type hw
 card 0
}

# Alias for digital (S/PDIF) output on the Audigy (hw:0,0)
# Do not use this directly--it requires specific rate,
# channels, and format
pcm.digital-hw {
 type hw
 card 0
 device 2
}

# Control device (mixer, etc.) for the Audigy card
ctl.digital-hw {
 type hw
 card 0
}

# Direct software mixing plugin for analog output on
# the Audigy (hw:0,0)
# Do not use this directly--it requires specific rate,
# channels, and format
pcm.dmix-analog {
 type dmix
 ipc_key 1234
 slave {
   pcm "analog-hw"
   period_time 0
   period_size 1024
   buffer_size 4096
   rate 48000
 }
}

# Control device (mixer, etc.) for the Audigy card
ctl.dmix-analog {
 type hw
 card 0
}

# Direct software mixing plugin for digital (S/PDIF) output
# on the Audigy (hw:0,0)
# Do not use this directly--it requires specific rate,
# channels, and format
pcm.dmix-digital {
 type dmix
 ipc_key 1235
 slave {
   pcm "digital-hw"
   period_time 0
   period_size 1024
   buffer_size 4096
   rate 48000
 }
}

# Control device (mixer, etc.) for the Audigy card
ctl.dmix-digital {
 type hw
 card 0
}


On 5/8/05, Michael T. Dean <mtdean at thirdcontact.com> wrote:
> 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
> _______________________________________________
> mythtv-users mailing list
> mythtv-users at mythtv.org
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>


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