[Intel-gfx] [Alsa-user] intel-hda: sound via HDMI only when using interlaced modes

[David Härdeman]

On Thu, Feb 07, 2013 at 11:00:13AM +0100, Daniel Vetter wrote:
>On Wed, Feb 06, 2013 at 10:35:33PM +0100, David Härdeman wrote:
>> I'll break etiquette here and include the entire original message below
>> (and top-post!) since I'm sending this to intel-gfx as well.
>> 
>> Since the previous mail I've tested a more recent kernel (3.8-rc6),
>> swapping HDMI cables and a firmware update on the receiver, none of it
>> helped.
>> 
>> I've also noticed that:
>> 
>> a) switching between 1080p30 and 1080p50 or 1080p60 is enough to make
>> the sound go away (higher frame rates) or work (1080p30). So, it has
>> nothing to do with interlacing.
>> 
>> The only difference between the output of all the intel*dump tools when
>> running 1080p30 and 1080p60 is included below. It's interesting to note
>> that all the modes that don't work have fdi_lanes = 2 while the working
>> ones have fdi_lanes = 1 (port width in intel_reg_dumper-speak).
>> 
>> I'm CC:ing the intel-gfx list as well as the ALSA list since I'm not su
>> sure where the problem lies anymore...suggestions?
>
>I'm far away from an hdmi/snd expert, but iirc the bandwidth to squeeze
>hdmi sound packets between the video frames is limited. And atm our code
>does not bother with checking for that at all (and updating the
>capabilities of the hdmi snd widget). But that's just an idea, I have no
>idea how much bandwidth there actually is.

I should add that I've now installed Win7 on a separate HD. Windows has
no problems at all with audio over HDMI, no matter which resolution
and/or refresh rate, so I think cabling and other HW issues can be ruled
out. The problem is Linux-specific.

And, as I mentioned before, the TV *is* willing to accept and decode the
audio signal, so it appears that the audio stream is there....but it's
probably incompatible in some minor way...and the receiver is being
picky. That's my guess.

Anyway, how should I proceed? File a bug? In the kernel bugzilla or ALSA
bugtracker or somewhere else?

//David