[alsa-devel] ALSA Multichannel through HDMI

John Ettedgui john.ettedgui at gmail.com
Fri Nov 26 01:53:53 CET 2010

On Thu, Nov 25, 2010 at 3:34 PM, John Ettedgui <john.ettedgui at gmail.com> wrote:
> On Thu, Nov 25, 2010 at 3:15 PM, Anssi Hannula <anssi.hannula at iki.fi> wrote:
>> On 26.11.2010 01:11, John Ettedgui wrote:
>>> On Thu, Nov 25, 2010 at 2:58 PM, Anssi Hannula <anssi.hannula at iki.fi> wrote:
>>>> On 26.11.2010 00:42, John Ettedgui wrote:
>>>>> On Thu, Nov 25, 2010 at 11:19 AM, Anssi Hannula <anssi.hannula at iki.fi> wrote:
>>>>>> On 25.11.2010 14:21, John Ettedgui wrote:
>>>>>>> On Thu, Nov 25, 2010 at 3:40 AM, Anssi Hannula <anssi.hannula at iki.fi> wrote:
>>>>>>>> On 25.11.2010 13:09, John Ettedgui wrote:
>>>>>>>>> On Thu, Nov 25, 2010 at 2:49 AM, Anssi Hannula <anssi.hannula at iki.fi> wrote:
>>>>>>>>>> On 25.11.2010 06:12, John Ettedgui wrote:
>>>>>>>>>>> I'm actually trying to get a 5.1 setup working without passthrough, if
>>>>>>>>>>> I use mplayer with passthrough my receiver behaves just fine, but I am
>>>>>>>>>>> trying to send the 6 channels from the computer.
>>>>>>>>>>> I was actually told that the current ALSA driver for radeon's hdmi
>>>>>>>>>>> does not support more than 2 channels, and that would explain why I'm
>>>>>>>>>>> getting this behavior. Is that true though?
>>>>>>>>>> Yes.
>>>>>>>>>> However, strangely your log output seems to show the intel's hdmi parser
>>>>>>>>>> being used instead:
>>>>>>>>>>> ALSA sound/pci/hda/patch_intelhdmi.c:842: hdmi_setup_stream: NID=0x2,
>>>>>>>>>>> stream=0x1, new-format=0x11
>>>>>>>>>> Were you just trying some patch at the time?
>>>>>>>>> yes Wu gave me a patch to try against the kernel, I'm guessing this is
>>>>>>>>> the reason you see something unexpected.
>>>>>>>> Did 6 channels work with that patch? (possibly with a wrong channel order)
>>>>>>> Not any better as far as I remember.
>>>>>> OK. Did 2 channel audio continue to work with it?
>>>>>> If you are not sure, here's the patch doing the same thing against
>>>>>> current alsa driver:
>>>>>> http://stuff.onse.fi/0001-ALSA-hda-Use-generic-HDMI-code-for-ATI-HDMI-codecs.patch
>>>>>> Confirming that would help (it would allow to switch the ATI chip to use
>>>>>> the generic parser instead of the ATI-specific one), though not with the
>>>>>> multichannel issue (see below).
>>>>>> [...]
>>>>>>>>> Since I just moved to jack/rca cables I'm in no hurry anymore, but is
>>>>>>>>> there any reason why the driver cannot work with more than 2 channels?
>>>>>>>> I don't really know (it is simply not implemented).
>>>>>>> Alright.
>>>>>>>>> Anything I could do to help with that?
>>>>>>>> Possibly. But see above, so that we won't try the same things you
>>>>>>>> already tried :)
>>>>>>> Sure :)
>>>>>> Looking again at the the alsa info output you provided, I don't think I
>>>>>> have any great ideas. It looks like the chip simply reports that it
>>>>>> supports a maximum of 2 channels.
>>>>>> One option could be hardcoding "chans = 8;" in generic_hdmi_build_pcms()
>>>>>> in sound/pci/hda/patch_hdmi.c (assuming you have the above patch and 2
>>>>>> channel audio works with it). However, I find it rather unlikely that it
>>>>>> would make any difference.
>>>>>> --
>>>>>> Anssi Hannula
>>>>> Anssi,
>>>>> the patch fails on my kernel, I cannot find the hda_codec_preset
>>>>> manually in there either.
>>>>> Did you want me to try that against a 2.6.37 rc instead of a 2.6.36?
>>>> For 2.6.36 I think you can just use your earlier patch.
>>>> Note that on that kernel generic_hdmi_build_pcms() is
>>>> intel_hdmi_build_pcms() in patch_intelhdmi.c.
>>> ok
>>>> BTW, I've just been informed by another ATI user that his card was
>>>> actually stereo-only, while he thought earlier it was multichannel
>>>> capable. So, are you sure your card is a multichannel one?
>>>> (if not, it would explain why the card says it is not)
>>>> --
>>>> Anssi Hannula
>>> Yes, it works fine in Window  so I believe the hardware part is good.
>> And you are sure it is multichannel PCM, and not e.g. multichannel DTS
>> or multichannel AC-3 with on-the-fly compression, which are possible
>> with stereo hdmi as well?
>> Just making sure :)
>> --
>> Anssi Hannula
> Well, I have not super tested it, but the reason I believe it is is
> simple, when I use passthrough my receiver says Dolby digital or
> something like that, but in Windows just going around or playing games
> it says Multichannel.
> I'll get the patch applied in a few minutes, I was running out of
> memory and my system was getting really slow... :)

I am not sure if I did it right but now I don't even get hdmi sound
working anymore.
It is not listed in aplay-l, and dmesg gives me this:
[drm:radeon_dvi_detect] *ERROR* HDMI Type A-1: probed a monitor but
no|invalid EDID

I've attached the patch I used, since I could not used the previous
one I had to hack it, maybe I broke something?
(I have not set channels to 8 yet, just changed the parser)

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