Arch Linux

xxxspuddy

Member

Registered: 2007-05-15

Posts: 57

[Solved] Mythtv audio capture woes

OK I admit it, after a week or so fighting with this, I'm stuck.

This is the last showstopper before using my mythbox as the primary entertainment source to my TV and would very much appreciate any help.

I'm running mythtv 0.20.2.20070828-2 built from ABS on Arch64 using the stock 2.6.23 kernel.  I have a Sound Blaster Live 5.1 (using coax digital out, just to complicate things a bit)  and a K-world v-stream xpert DVB-T card with composite/s-video input.  My cable box is plugged into the video input and the soundcard line-in.  The picture is fine, but the problem is that I cannot get Mythtv to capture the audio from the soundcard at all. 

I have set /dev/dsp to be the audio device in mythtv-setup and `cat /dev/dsp > /dev/dsp` does output the audio from the cable box.

Doing an lsof when trying to watch tv:

# lsof /dev/dsp
COMMAND     PID USER   FD   TYPE DEVICE SIZE  NODE NAME
mythbacke 22451 root   24r   CHR   14,3      10225 /dev/sound/dsp

Doesn't seem to be a permissions issue either as its the same problem running the frontend as root.  Searching through forums seems to point the blame at my mixer levels, though I think I've tried every combination!

In alsamixer, under playback, everything muted, under capture Line and Capture are set to capture, Capture and AC97 are set to 100 = No Sound

If I then increase the AC97 playback volume I get the Live TV audio direct from the cable box which is out of sync and not recorded.

No doubt I've missed something really obvious, so please give me a kick in the right direction.

Thanks

Last edited by xxxspuddy (2007-12-07 15:52:58)

---

A temporary file is just a pipe with an attitude and a will to live.

sinister99

Member

Registered: 2007-04-10

Posts: 136

Re: [Solved] Mythtv audio capture woes

Does your capture card have sound input?  If it does, try using that, it was easy to set up on my hauppauge.

xxxspuddy

Member

Registered: 2007-05-15

Posts: 57

Re: [Solved] Mythtv audio capture woes

No it doesn't, that's why I'm using the soundcard line-in.

---

A temporary file is just a pipe with an attitude and a will to live.

timm

Member

From: Wisconsin

Registered: 2004-02-25

Posts: 417

Re: [Solved] Mythtv audio capture woes

I had a similar problem but not on the same setup; I ended up muting and unmuting channels in alsamixer one at a time and eventually got it to work; unfortunately, I did not document my work and can't tell you what I found the ultimate "right" setting to be.  Might be worth a try.

xxxspuddy

Member

Registered: 2007-05-15

Posts: 57

Re: [Solved] Mythtv audio capture woes

hmm...I've tried that too but no success

I've also tried using a different sound card, two sound cards and standard line-out instead of coax.  After looking at this howto

http://www.arock.dk/mythtv-doc/mythtv-H … ting_Audio

I've tried:

$ aplay /dev/dsp

and this gets the expected output. 

"Once this test succeeds, MythTV should work correctly because it writes to and read from /dev/dsp in the same way that aplay does."

But it still doesn't work

Any more suggestions?

Thanks!

---

A temporary file is just a pipe with an attitude and a will to live.

xxxspuddy

Member

Registered: 2007-05-15

Posts: 57

Re: [Solved] Mythtv audio capture woes

Some more progress...

I installed mythtv on a networked system and run the frontend as another test and amazingly the sound and video are in sync!  So the sound is definitely being captured by mythtv.

But it still doesn't work on my combined front/backend system.  Interestingly, when playing back livetv recordings on this box, dvb-t recordings are fine but the analog recordings dont have sound.  On the networked system, both have sound.

---

A temporary file is just a pipe with an attitude and a will to live.

xxxspuddy

Member

Registered: 2007-05-15

Posts: 57

Re: [Solved] Mythtv audio capture woes

I knew this would be something simple!  When running the frontend from a terminal, these errors pointed me in the right direction:

2007-12-06 13:45:17.078 AudioOutput Error: Rate doesn't match (requested 44100Hz
, got 48000Hz)
2007-12-06 13:45:17.078 AudioOutput Error: Unable to set ALSA parameters
2007-12-06 13:45:17.078 NVP: Disabling Audio, reason is: Unable to set ALSA para
meters

In Utilities/Setup->Setup->General my audio output device was set to ALSA:spdif but I have an /etc/asound.conf file that makes the spdif output the default, so changing the device to ALSA:default solved the problem.  I am a happy bunny

Now how do I mark this topic solved?

---

A temporary file is just a pipe with an attitude and a will to live.

timm

Member

From: Wisconsin

Registered: 2004-02-25

Posts: 417

Re: [Solved] Mythtv audio capture woes

You can go back to your original post, click on edit, and then just add [solved] or such to the topic line.  Glad to know you got it working.