[mythtv-users] mythmusic iec958 help

Alen Edwards allen.edwards at oldpaloalto.com
Sun Jul 6 16:29:57 UTC 2008


I just did some testing over the last 3 hours and here is what is working:

Audio output device:  ALSA:spdif
Passthrough output device:  ALSA:iec958:(AESO 0x02)
Max Audio Channels:  Stereo
Upmix: passive
Enable AC3 to SPDIF passthrough  CHECKED
Enable DTS to SPDIF passthrough  CHECKED
Use internal volume NOT CHECKED
Aggressive sound  NOT CHECKED

/etc/X11/asound.conf   REMOVED
.asouncrc   NOT THERE

Under these conditions I get these results:
MythTV = DD (working.  Sound from all speakers)
MythMusic = PCM (working.  Responding normally)
Firefox Internet Flash = Analog out  (acceptable but not ideal)

Flash apparently does its own sound processing and does not have an 
option I could find to make it digital.

The logs are confusing as they open lots of audio devices before 
settling in on the one I would expect.
For TV:
Opening audio device 'spdif'. ch 2(2) sr 48000
Opening ALSA audio device 'iec958:{ AES0 0x02 }'.

For CD:
Opening audio device 'spdif'. ch 2(2) sr 44100
Opening ALSA audio device 'spdif'.

For Flash:
No audio entries in log.  I believe this confirms I cannot change flash 
sound with myth setup.

As far as the question on 0x02 and 0x06 goes, I issued these two 
commands while audio was playing:

$ iecset
Mode: consumer
Data: non-audio
Rate: 48000 Hz
Copyright: protected
Emphasis: none
Category: PCM coder
Original: original
Clock: 1000 ppm

$ iecset -x
AES0=0x02,AES1=0x82,AES2=0x00,AES3=0x02

That would indicate that AES0 0x02 is the correct setting for my sound 
card, per some googling.

So, I think for my audio device (Intel HDA) that these settings are 
working as desired with the exception of Flash, but I don't think myth 
can't do anything about that.


Allen


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