[mythtv-users] SPDIF surround broken in trunk

Greg Woods greg at gregandeva.net
Sat Jul 17 16:09:57 UTC 2010

On Sun, 2010-07-18 at 01:34 +1000, Jean-Yves Avenard wrote:
> Starting to help would be to actually describe what issue you're
> having instead a very long version of "it doesn't work"

I have already done this; there has been a long thread. I have posted

> > If there is anything else I can do to help troubleshoot my problem or if
> > anyone else has seen surround sound break in recent updates, please let
> > me know. I cannot completely rule out something I may have messed up
> > with settings or the database, but the bottom line is that surround
> > sound was working, I did an svn up and recompiled, and now surround
> > sound is not working. I don't know how else to get it working other than
> > going back to a previous version where it worked. I suppose it will be
> > interesting to see whether or not this is successful.
> Did you update to the version I mentioned earlier, that should fix the
> AC3 and DTS flag not showing up with your card?

Yes, I am currently running 25339, more recent than the 25334 you
recommended. These are the screenshots that I posted.

> You will not get surround sound unless AC3 and/or DTS box are checked
> with SPDIF output.

OK, so it sounds like my problem is that I'm not seeing those
checkboxes, so presumably it doesn't think any of my output devices are

> what does aplay -L and aplay -l shows on your box.

Bizarre. -L shows none of the devices are digital, even the IEC958 shows
as analog despite having "digital" in the description. -l shows that
there is a digital output. But I haven't updated anything other than
Myth on this box in many moons; it is still running Fedora 10. What
should I look for in alsamixer in case I have messed something up trying
to get this to work? I checked for the obvious and the IEC958 device is
not muted but the IEC958 loop is. These show up as "S/PDIF" and "S/PDIF
L" in the terminal version of alsmixer. There is also a slider labeled
"Digital" which is not muted.

> When you select ALSA:iec958 in the list, you should have 3 checkboxes
> showing up, the first one is visible but disabled, the 2nd one is AC3

Right, but as shown in the screenshots, there are no checkboxes.

[root at confusion trunk]# aplay -L
    C-Media CMI8788, Analog
    Default Audio Device
    C-Media CMI8788, Analog
    Front speakers
    C-Media CMI8788, Analog
    4.0 Surround output to Front and Rear speakers
    C-Media CMI8788, Analog
    4.1 Surround output to Front, Rear and Subwoofer speakers
    C-Media CMI8788, Analog
    5.0 Surround output to Front, Center and Rear speakers
    C-Media CMI8788, Analog
    5.1 Surround output to Front, Center, Rear and Subwoofer speakers
    C-Media CMI8788, Analog
    7.1 Surround output to Front, Center, Side, Rear and Woofer speakers
    C-Media CMI8788, Analog
    IEC958 (S/PDIF) Digital Audio Output
    Discard all samples (playback) or generate zero samples (capture)
[root at confusion trunk]# aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: CMI8788 [C-Media CMI8788], device 0: Analog [Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: CMI8788 [C-Media CMI8788], device 1: Digital [Digital]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

> What's the resolution of your screen?

I believe the physical TV pixels are actually 1024x768, however the TV
can and does accept HD input. The TV says that the input signal is
1920x1080 (either from HDMI on the computer or directly from the cable
STB), so that is what X is generating. 


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