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

[Luís Mendes]

Hi Russell,

I'm using the following sound sample for aplay:
http://www.kozco.com/tech/piano2.wav
from this site:
http://www.kozco.com/tech/soundtests.html

The sample file plays without an issue on SGTL5000 chip, but no sound on
HDMI.
I've tested with a CROWN TV and a SAMSUNG TV, no sound on neither.
The sound file fulfills the requirements that you have pointed out: stereo,
48kHz, S16_LE.

Could there be an issue with the driver? Could this be a DTB definition
issue?

Below the output log for aplay with the above sound file.

Regards,
Luís

aplay -t wav -D front:CARD=DWHDMI,DEV=0 --dump-hw-params
Downloads/piano2.wav
Playing WAVE 'Downloads/piano2.wav' : Signed 16 bit Little Endian, Rate
48000 Hz, Stereo
HW Params of device "front:CARD=DWHDMI,DEV=0":
--------------------
ACCESS:  MMAP_INTERLEAVED MMAP_NONINTERLEAVED RW_INTERLEAVED
RW_NONINTERLEAVED
FORMAT:  S16_LE S16_BE S32_LE S32_BE S24_3LE
SUBFORMAT:  STD
SAMPLE_BITS: [16 32]
FRAME_BITS: [32 64]
CHANNELS: 2
RATE: [32000 48000]
PERIOD_TIME: (666 32000]
PERIOD_SIZE: [32 1024]
PERIOD_BYTES: [128 8192]
PERIODS: [2 16]
BUFFER_TIME: (1333 512000]
BUFFER_SIZE: [64 16384]
BUFFER_BYTES: [256 131072]
TICK_TIME: ALL
--------------------


On Mon, Nov 6, 2017 at 4:25 PM, Russell King - ARM Linux <
linux at armlinux.org.uk> wrote:

> 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.
>
> --
> RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
> FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps
> up
> According to speedtest.net: 8.21Mbps down 510kbps up
>
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