[Expired for alsa-driver (Ubuntu) because there has been no activity for
60 days.]
** Changed in: alsa-driver (Ubuntu)
Status: Incomplete => Expired
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https://bugs.launchpad.net/bugs/1296017
Title:
ALSA Not Selecting Correct Output Channel Map
Status in “alsa-driver” package in Ubuntu:
Expired
Bug description:
Hi All
As preface to this question, please know that I'm a complete noob with Linux
- forgive my lack of understanding the basics, and any dumb questions that may
give rise to.
The issue - possible ALSA driver bug - is experienced when running
xbmc, via OpenELEC. Playback of multichannel FLAC files is failing
with 4.0-CH surround music (ie: Quadraphonic). PB fails inasmuch as
xbmc sends the audio (MCH-PCM > HDMI > AVR) in a format incompatible
with the AVR.
After much dialogue with the relevant xbmc devs, I've been told this is a
driver problem (ALSA), and to report it here at Launchpad.
(FYI: discussion begins here ->
http://forum.xbmc.org/showthread.php?tid=170338&pid=1638835#pid1638835, see
posts by "gjwAudio" )
What Happens:
4.0 audio is output over HDMI as FL,FR,BL,BR, but my AVR does not recognize
this format, and defaults to 2-CH (stereo) - no back channel information.
What Should Happen:
4.0 audio should be sent as 5.1 PCM, with appropriate "extra" channels muted.
Hypothesis:
ALSA is not flagging 4.0 channel map as invalid for this receiver (based on
audio-related EDID info), and xbmc configures 1:1 output mapping (FL,FR,BL,BR >
FL,FR,BL,BR).
Testing in OpenELEC:
Three FLAC sample files were used: 3.0, 4.0 and 5.1 channels. xbmc configured
both 3.0 & 5.1 files as 5.1 PCM, and played correctly through the AVR. The 4.0
file was configured 1:1, and the back channels failed to play.
When setting xbmc for global fixed output of 5.1 channels, all three
files played correctly - however, this fixed setting also locks the
sample rate, and forces unnecessary re-sampling, depending on the
particular song being played. It also prevents legitimate upmixing of
2.0 video soundtracks to "surround".
The xbmc devs explain the behaviour thus:
( http://forum.xbmc.org/showthread.php?tid=170338&pid=1651346#pid1651346 )
"This happens when opening 3.0 (FL,FR,FC)
- you can't have gaps, and in ALSA map, FC is at pos 5 (FL,FR,BL,BR,FC)
- only even numbers of channels are allowed
This is why 3.0 opens as 5.1.
4.0 as FL,FR,BL,BR is valid, and most devices don't have issues with
this. We can't just open 5.1 for this case. "
--and-- (regarding the new audio engine "ActiveAE")
( http://forum.xbmc.org/showthread.php?tid=170338&pid=1651708#pid1651708 )
"ActiveAE plays no role in this scenario. It is the ALSA sink and the driver.
The driver should not open in 4.0 mode if the device does not support it. This
needs to be fixed in the driver. Others will complain if we opened 4.0 as 5.1
because this would disable upmixing in the AVR. "
--and--
( http://forum.xbmc.org/showthread.php?tid=170338&pid=1655015#pid1655015 )
"If you don't have configured fixed mode, XBMC tries to open the channels
layout with best match to the input stream. In case this is FL,FR,BL,BR - which
also matches ALSA channel map, we try to open this layout. If the audio device
does not support this format, ALSA should fail opening. Then we try the next
layout which would be 5.1 in this case."
--and--
( http://forum.xbmc.org/showthread.php?tid=170338&pid=1655895#pid1655895 )
"If ALSA opens that mask, then that's a driver problem and should be reported
upstream to the ALSA devs."
Testing in Windows:
As another check on the xbmc audio output logic, I was asked to run the same
FLACs through a Windows install (same beta release version of xbmc).
All files played correctly under Windows. Please note the "5.1 PCM"
indicator lit up on the AVR, for every file. This suggests the correct
EDID info was available to xbmc through the Windows driver(s).
Linux Setup:
OpenELEC v4.0 beta 2 (Gotham) - Generic x86_64; Intel 847 Celeron NUC,
KVR1333D3S9/4G RAM, Kingston SMS200S3/30G mSATA > 2m HDMI > Anthem Statement D2
(AVR) > Samsung PN51E6500.
Windows Setup:
xbmc v13.0 beta2 (Gotham), Asus X502C - i3-3217U, 4 GB RAM, Intel HD 4000
graphics, Win 8.1 > 2m HDMI > Anthem Statement D2 (AVR) > Samsung PN51E6500.
It is useful to know, the same fault occurs under OpenELEC stable
build v3.x.
I hope this is enough information to begin looking into why the EDID
info is not getting through to the xbmc software.
Thanks in advance for your help and consideration.
Grant
Sample FLACs:
https://db.tt/AaMpYdPJ
https://db.tt/DfNjgb1t
https://db.tt/n40qUvHI
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