[alsa-devel] Radeon unconnected HDMI eats samples at 280 kHz

[David Henningsson]

On 2014-09-19 20:19, Alexander E. Patrakov wrote:
> 19.09.2014 23:47, David Henningsson wrote:
>> If audio_enabled quickly changes to off and then on when there is a mode
>> change, it might make sense to *not* wake up the audio driver in this
>> case, as I assume that the audio capabilities on the HDMI TV will not
>> change just because the video mode changes.
>
> Unfortunately, they will. Some low-resolution video modes just don't
> have enough pixel clock to transfer the 7.1 audio signal at 192 kHz. See
> the table on page 105 (shown as 121 in some readers) of
> http://www.microprocessor.org/HDMISpecification13a.pdf , section "7.3.3
> Video Dependency".

Ok, I stand corrected. I wonder what the least ugly thing to do would be 
if the user is currently running audio when this happens, e g, if the 
user is running a game with background music, and goes to "video 
settings" and switches mode.

But if such thing would audio glitch anyhow, like it seems maybe we 
should let the audio_enabled signal pass through to the audio side to 
indicate a short disconnection. It's just not going to be that fun 
if/when we implement reprobing the HDMI device on plug in. And also the 
risk of the audio stream switching to somewhere else, like going from 
HDMI to analog.


-- 
David Henningsson, Canonical Ltd.
https://launchpad.net/~diwic