[mythtv-users] Re: Audio Woes

Ben Matthew ben at thelemite.freeserve.co.uk
Wed Aug 25 07:45:36 EDT 2004

On 19/08/2004 03:42, Michael T. Dean wrote:

>Are you sure you were using OSS drivers?  They've been deprecated in 
>favor of ALSA for the 2.6 kernel series.  Usually, you want to use ALSA

>drivers with ALSA's OSS emulation support.

Although deprecated they are still included with the 2.6.7 kernel.  So I
Have tried both OSS emulation through ALSA and the OSS drivers.

>>worth of samples seem to get stuck in a loop jamming the system for
>>about 5 seconds; "dah-dah-dah-dah-dah..." to be scientific.  Then
>>mythfrontend reappears and everything returns to normal.
>Most sounds cards do not provide hardware "direct mixing" support.  

No this is not a blocked device issue.  The samples being stuck are
Noticably from the DVB stream.  Besides I made sure no other processes
Were running that might possibly try to open the sound device.

>If you used "-ao ALSA:driver=iec958" MPlayer should not have given you 
>sound; "-ao alsa1x:iec958" (or "-ao alsa9:iec958" depending on your 
>version of MPlayer) might have worked...

Well the version of Mplayer I have built; MPlayer 1.0pre5-3.3.3, uses
That argument format to specify ALSA devices.  I can quite assure you
It does work; given I typed that in and it played back through my
Output perfectly.

>So, how can you fix this?  I recommend first creating a proper


I have now created this file, forcing audio data through the dmix plugin
That autoconverts into 48000 hz.  The results, however, are even worse!!

A/V sync is completely out; sound is just a load of jitters.  I get lots
Audio buffer overrun messages and eventual seg fault.  If I specify
As my output device (instead of mixed-digital) I get exactly the same
As specifying ALSA:iec958 - i.e: perfect for 10 seconds then audio loss
A broken pipe error.

Mplayer works perfect using "-ao ALSA:driver=digital" now but refuses to
Work with "-ao ALSA:driver=mixed-digital" which makes me wonder if
Is amiss with my .asoundrc file, below.  Any ideas?

(my soundcard chipset, for reference, is the via8235)


Ben Matthew


# .asoundrc for digital output over SPDIF on a snd_via82xx supported
# soundcard

pcm.digital {
type plug
slave.pcm "digital-hw"

ctl.digital {
type hw
card 0

pcm.mixed-digital {
type plug
slave.pcm "dmix-digital"

ctl.mixed-digital {
type hw
card 0

pcm.digital-hw {
type hw
card 0
device 1
subdevice 0

ctl.digital-hw {
type hw
card 0

pcm.dmix-digital {
type dmix
ipc_key 1235
slave {
pcm "digital-hw"
period_time 0
period_size 1024
buffer_size 4096
rate 48000

ctl.dmix-digital {
type hw
card 0

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