[alsa-devel] [PATCH 00/19] Rework OMAP4+ HDMI audio support

Joachim Eastwood manabian at gmail.com
Sat May 17 10:51:53 CEST 2014

On 14 May 2014 18:25, Joachim  Eastwood <manabian at gmail.com> wrote:
> On 14 May 2014 12:02, Jyri Sarha <jsarha at ti.com> wrote:
>> On 05/13/2014 12:13 AM, Joachim Eastwood wrote:
>>> On 12 May 2014 11:12, Jyri Sarha <jsarha at ti.com> wrote:
>> ...
>>> hey, this worked straight away :)
>>> But there seems to be something wrong with the channel mapping.
>>> For stereo (speaker-test -c 2) the mapping is correct.
>>> But for -c 4 and -c 8 it gets weird:
>>> speaker-test -c 4 -s X # where X is 1-4
>>> 1: Front Left is Rear Left
>>> 2: Front Right is Rear Right
>>> 3: Rear Right is Front Right
>>> 4: Rear Left is Front Left
>>> speaker-test -c 8 -s X # where X is 1-8
>>> 1: Front Left is Rear Left
>>> 2: Center is Rear Left
>>> 3: Front Right is Rear Right
>>> 4: Side Right is Front Right
>>> 5: Rear Right is silent
>>> 6: Rear Left is Center
>>> 7: Side Left is Front Left
>>> 8: LFE - Rear Right
>>> I think you need to check what channel order ALSA expects. I believe
>>> speaker-test does the right thing on my HTPC normally connected to my
>>> receiver.
>> I checked the implementation and there was indeed something weird there, but
>> the implementation can not explain the FL and FR channels jumping around. FL
>> and FL should always be the first two channels in all configurations and the
>> implementation does not touch them.
>> The implementation uses 8ch HDMI setup for anything above 2ch with "Audio
>> InfoFrame Data Byte 4" set to 0x13. According to CEA-861 specs this means
>> following channel order: FL, FR, LFE, FC, RL, RR, RLC, RRC
>> This is a closest match to ALSA 8ch mapping (according to
>> sound/core/pcm_lib.c) which is: FL, FR, FC, LFE, RL, RR, SL, SR
> hm, okey. I haven't look at the code but it do seem strange. But with
> speaker-test -c 4 the front and back are surely swapped here.
> I'll do some more testing and also check with my HTPC. btw, I only
> have a 5.1 setup over here so I can't test all the discrete channels.
>> Current implementation has FLE and FC channels correctly swapped, but it
>> shifts them to last two channels and RL, RR, SL, SR are shifted down to fill
>> the place. This is all wrong and I'll try to come up with a fix for that.
>> Unfortunately I can not test anything beyond 2 ch myself so I would need
>> someone to volunteer to test my patch.
> I have the dev kit setup up over here so I can test your patches.

I did some more testing over here.

My HTPC (nVidia ION2 based) works good with speaker-test and all
channels are where they are suppose to be.

On the OMAP4 board I tried doing: "while true; do speaker-test -c 4 -s
1; done" and this had an interesting effect.
Most of the time FL (Front Left) is swapped with BL (Back Left) but
about every 10th time the sound comes out in the FL speaker... So
there something weird going on here. Same story for the right channel.

I also noticed that HDMI doesn't always work on boot up, it sometimes fail with:
[ 193.985565] omapdss_hdmi 58006000.encoder: audio not supported
[ 193.985565] omapdss_hdmi 58006000.encoder: ASoC: can't open
interface 58006000.encoder: -19

But after replugging the HDMI connector a couple of times it starts to work.

I'll see if I can try with an old TI OMAP4 kernel (3.4) and see how that works.

Joachim Eastwood

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