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Problem: 192khz over HDMI
#1
Hello, sorry if this question has been answered before but I've been searching the forum threads with no luck.
It seems that Moode has supported 192khz over HDMI at some point in time:

  3.8 Release 2017-07-31
  New features
  - NEW: HDMI audio interface support for 24 bit 192 kHz

The fact is I can't get 192khz over HDMI in Raspberry's Moode 4.4 and everything is resampled to 48khz.
Is there any way to avoid 48khz downsampling?

Thanks Smile
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#2
The Linux kernel source header shows 192K supported over HDMI.
https://github.com/raspberrypi/linux/blo...nux/hdmi.h

Maybe there is some sort of compatibility issues between Linux and the HDMI connected audio device ??
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#3
(01-18-2019, 02:12 AM)Tim Curtis Wrote: The Linux kernel source header shows 192K supported over HDMI.
https://github.com/raspberrypi/linux/blo...nux/hdmi.h

Maybe there is some sort of compatibility issues between Linux and the HDMI connected audio device ??

Hi Tim, My Raspy is connected to a Marantz AVR and not downsampling 192khz streams in Kodi distros (I know Kodi use its own AudioEngine)

Found this https://github.com/raspberrypi/linux/blo...2835-pcm.c

It seems even though the kernel header already include 192k, the alsa driver is built with rate_max = 48000. Isn't it?

I wonder whether it could be possible to build next Moode releases with rate_max = 192000 and 24bit depth format. Maybe is not trivial and could involve applying special patches...

Thanks Shy
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#4
I have no idea whether that's the driver invoked for HDMI audio out. I don't do any kernel hacks anymore because of the support burden so your best bet is to submit your issue to the Linux kernel devs. They are very responsive. https://github.com/raspberrypi/linux/issues

Be sure to include sufficient information including the audio file format, the type of audio device and the contents of /boot/config.txt. Also if you have a success case e.g. " The file plays at the correct rate when using an I2S DAC" then mention that as well.

-Tim
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#5
(01-18-2019, 01:36 PM)Tim Curtis Wrote: I have no idea whether that's the driver invoked for HDMI audio out. I don't do any kernel hacks anymore because of the support burden so your best bet is to submit your issue to the Linux kernel devs. They are very responsive. https://github.com/raspberrypi/linux/issues

Be sure to include sufficient information including the audio file format, the type of audio device and the contents of /boot/config.txt. Also if you have a success case e.g. " The file plays at the correct rate when using an I2S DAC" then mention that as well.

-Tim

Thanks Tim, I will investigate further but I've found some issues already submitted about hires, multichannel audio and the alsa driver. I've seen some commits not merged in the stable branch.

I think actually no distro is supporting hires audio over HDMI without bypassing the alsa driver.
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#6
Sorry for the hijack of the thread a bit...

But would that mean also that so far it is not possible to do bit perfect DSD over HDMI?
Or there is a way to bypass Alsa drivers?

I am still looking for a way to play 2.0 and 5.1 DSD files like I do with SACD from a Bluray player to my receiver via HDMI.
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#7
(01-30-2019, 04:48 AM)mimizone Wrote: Sorry for the hijack of the thread a bit...

But would that mean also that so far it is not possible to do bit perfect DSD over HDMI?
Or there is a way to bypass Alsa drivers?

I am still looking for a way to play 2.0 and 5.1 DSD files like I do with SACD from a Bluray player to my receiver via HDMI.

I am afraid that is not even possible to play any hi-resolution format via HDMI. Forget bit perfect with MPD and HDMI out.
You should check if latest Kodi Leia can play DSD format. I think it can play DSF/DFF files but with PCM conversion.
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#8
I think alsa cannot by default (I think there are some edits to do and recompile it to work). 
One could bypass alsa and use Broadcom Openmax APIs. IIRC it works that way and outputs multi channel (7.1 iirc) linear PCM via HDMI.
I am sure someone using it to do 3 way active software crossovers using multi channels A/V receivers Big Grin

google "openmax raspberry pcm hdmi" or something like that and you'll find what I mean.
e.g.
https://www.raspberrypi.org/forums/viewt...hp?t=50630
https://yabb.jriver.com/interact/index.p...ic=97510.0
https://www.raspberrypi.org/forums/viewt...p?t=116953


some context about alsa multichannel in linux kernel:
https://github.com/raspberrypi/linux/pull/1166
https://github.com/raspberrypi/linux/issues/1000
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