Question regarding HDMI Audio support on i.MX6 with vanilla kernel

[Russell King - ARM Linux]

On Mon, Nov 06, 2017 at 03:46:51PM +0000, Luís Mendes wrote:
> I've checked the interrupts for 120000.hdmi and they do increment with
> aplay without the sound server, as well as when the sound server is loaded
> and I play audio files with mpv or vlc.
> The sgtl5000 unit is playing audio on analog output fine, only the digital
> outputs don't produce sound.
> Still haven't checked what happens when unloading the kernel modules for
> the other audio devices... I will have to compile the kernel with such
> devices defined as modules, so that I can unload or blacklist them.

If the interrupts are incrementing while playing audio, then audio is
being sent to the device.  There may be some reason that the device
decides it doesn't like the audio.

The minimum audio requirements if audio is supported are 2-channel,
32kHz, 44.1kHz or 48kHz audio.  Anything beyond that requires additional
specification by the TV, and if you try to send it something it doesn't
support, the TV can decide to mute the audio.

Also remember that audio is a side-channel to the video - it is sent to
the HDMI sink in the blanking intervals, and the audio clock is derived
from the video clock.  So, audio is dependent on the video path being
active.

I've tested it with a Panasonic smart tv, an Onkyo AV receiver, a Yamaha
AV receiver, and a el-cheapo rebranded tv, which all worked fine.

-- 
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