[ALSA - driver 0001651]: ac3 passthrough not really work with ac3dec

[bugtrack@alsa-project.org]

A NOTE has been added to this issue.
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<https://bugtrack.alsa-project.org/alsa-bug/view.php?id=1651> 
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Reported By:                tycordinal
Assigned To:                
======================================================================
Project:                    ALSA - driver
Issue ID:                   1651
Category:                   PCI - emu10k1
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     new
Distribution:               
Kernel Version:             2.4.31
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Date Submitted:             12-14-2005 09:44 CET
Last Modified:              12-14-2005 10:53 CET
======================================================================
Summary:                    ac3 passthrough not really work with ac3dec
Description: 
using the following from alsa-tools to play ac3 as passthrough:
ac3dec -C oneac3file.ac3 


the ac3dec is able to "open" the spdif device "iec958:{AES...}" and did
not report any error and keep on running, but the ac3 decoder (creative
ddts-100), connected to the "spdif output" from the card, did not switch
to dolby mode, and no sound come out from speaker.

one interesting thing is, when I run this:
ac3dec -6 oneac3file.ac3 

As this is software decoding to PCM, I can hear the left/right channels
from the front stereo jacket, as they also output on the "spdif output".
Therefore, I believe the "spdif output" on the card is indeed working,
just that for this card we might need to write some different AES command
to open the spdif output?

I am not sure if the alsa config files in /usr/share/alsa have to change
or maybe some "switches" in emu10k1_main.c needs to apply for the "spdif
output" to  really behave as "iec958" device to passthough ac3 stream to
external decoder.

Thanks.





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----------------------------------------------------------------------
 tycordinal - 12-14-05 10:31 
----------------------------------------------------------------------
interesting things:

when doing ac3dec -6 oneac3file.ac3 ,
there is sound coming out from the spdif output, and when i use alsamixer
to make "IEC958 Optical Raw" from "MM" to become "OO", the sound stop
coming out. When I make it as "MM", the sound come back again. In this
case, alsamixer can toggled the sound output, if spdif output is playing
digital stereo.

when doing ac3dec -C oneac3file.ac3,
alsamixer show "IEC958 Optical Raw" as "OO" , and there is no dolby light
on the decoder (creative DDTS-100). when I make it "MM", there is still no
dolby light.  when I exit alsamixer and run alsamixer again, "IEC958
Optical Raw" has become "OO". In this case, alsamixer cannot help to get
ac3 passthough from the spdif output, because it cannot really make
"IEC958 Optical Raw" as "MM", even though it seems it can. After ac3dec
finished, "IEC958 Optical Raw" back to "MM" again, as shown by running
alsamixer again.

----------------------------------------------------------------------
 pzad - 12-14-05 10:53 
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IEC958 Optical Raw - this is just multiplexer switch.
If there is MM - this means spdif output comes from DSP and from normal
playback device.
If there is OO - spdif output comes from iec958 (or spdif) device.

Please do, what I suggest you in previous note.
Your problem is "Audigy Analog/Digital Output Jack" control.

Issue History
Date Modified  Username       Field                    Change              
======================================================================
12-14-05 09:44 tycordinal     New Issue                                    
12-14-05 09:44 tycordinal     Kernel Version            => 2.4.31          
12-14-05 10:05 tycordinal     Note Added: 0007031                          
12-14-05 10:15 tycordinal     Note Added: 0007032                          
12-14-05 10:16 tycordinal     Note Added: 0007033                          
12-14-05 10:30 pzad           Note Added: 0007034                          
12-14-05 10:31 tycordinal     Note Added: 0007035                          
12-14-05 10:53 pzad           Note Added: 0007036                          
======================================================================




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