[alsa-devel] ALSA Multichannel through HDMI

Mohammad Bahathir Hashim bahathir at gmail.com
Thu Nov 25 06:10:34 CET 2010

On 2010-11-25, John Ettedgui <john.ettedgui at gmail.com> wrote:
> On Wed, Nov 24, 2010 at 7:59 PM, Mohammad Bahathir Hashim
><bahathir at gmail.com> wrote:
>> On 2010-11-24, John Ettedgui <john.ettedgui at gmail.com> wrote:
>>> On Tue, Jan 12, 2010 at 9:02 PM, Wu Fengguang <fengguang.wu at intel.com> wrote:
>>> I am sorry to resurrect this thread after so long, but I still have
>>> not been able to get anywhere.
>>> Also it just came to my attention that if my receiver always sees the
>>> hdmi connection as stereo (apart from when using ac3/dts passthrough)
>>> channel remapping is not the solution, but somehow something else is
>>> messed up.
>>> I think I should try some options in modprobe.conf for snd-hda-intel
>>> but I am not sure which ones, and from all the examples I can find on
>>> the web, it seems none of them are talking about a radeon hdmi
>>> connection...
>>> So I'm asking for advice here again :)
>>> Thanks!
>>> _______________________________________________
>>> Alsa-devel mailing list
>>> Alsa-devel at alsa-project.org
>>> http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
>> Hi, I think there are developments in ffmpeg projects, to support
>> multichannel passthrough through HDMI, ALSO only provides infra and
>> interface to the HDMI. The passthrough decoding is handled by apps.
>> Here is the snippet from the ffmpeg's 'svn log'
>> ------------------------------------------------------------------------
>> r25760 | cehoyos | 2010-11-17 20:22:59 +0800 (Wed, 17 Nov 2010) | 6 lines
>> Add support for IEC 61937 ("SPDIF") encapsulation for E-AC-3.
>> Only works via HDMI.
>> Patch by Anssi Hannula (anssi d hannula a iki d fi), based on some work
>> by myself.
>> ------------------------------------------------------------------------
>> You can search in ffmpeg's development's mailing list for more information.
>> Thank you.
> Hey Mohammad,
> 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?
> Thanks!
> John

Currently, I don't have HT AVR with HDMI, but for normal SPDIF through
TOSLINK will stream any standard 5.1 DTS/AC3 raw bitstream to my cheap
AVR (Yamaha RX-V361) without any problem.

$ mplayer -ao alsa:device=spdif -ac hwdts,hwac3, foo.mkv

It is not about how many channels that HDMI can support, but how to
pass the bitstream correctly to the receiver.  As we can see in this
thread, the support for higher bandwidth/format of the DTS/AC3 format
is currently being developed by Anssi Hannula. 


Eventually it will be incorprated in MPlayer-svn.

Thank you.

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