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Some days ago I installed Fedora 22 on my media center pc. Previously I had Windows 8 installed because I wanted to play some games and watch some blurays, and everything worked as wanted. The HDMI sound output from the AMD R9 270x graphics card worked as it should, streaming PCM, DTSHD-MA, TrueHD etc.

After I installed Fedora 22, the sound output from the R270x-card is not working. As I use the machine as a media center I have not installed PulseAudio and I am currently using ALSA. The HDMI output is detected but the sound is broken. When I manually set the HDMI output and play a sound, the sound seems to be looping and the output is not correctly set. The number of channels is not correctly set and my receiver output noise.

I thought that the passthrough might work, but it does not. At best it switches between DTS and DTSHD-MA when playing THX Amazing Life. Another problem is that the passthrough does not work when I set the refresh rate to equal that of the video. When the refresh rate is 60 Hz, some data is passed to the receiver.

As of now I suspect it is a driver problem. When I switch to the internal Intel graphics/sound card both PCM and passthrough work with no additional configuration. The passthrough even works when I set the refresh rate to match the video refresh rate and the THX Amazing Life and the Dolby Atmos Leaf videos play as they should.

I could disable the AMD card, but I want to be able to play some games as I plan on installing Steam in addition to Kodi.

A solution I stumbled over was to change some of the alsa settings. I found that the PCM output from Kodi worked when I had the following in my .asoundrc:

pcm.!default {
    type lfloat
    slave.pcm "hdmi:HDMI,0"
    slave.format S32_LE
}

Bitstreaming did not work with this setting.

Is it possible to get my AMD card to correctly output audio (PCM and bitstream) via HDMI?

UPDATE I've currently upgraded to the newest kernel available in the Fedora 22 repositories (Linux kernel 4.0.5) and now the 270x HDMI audio is working as it should. I haven't tried to bitstream HD audio formats yet, but at least PCM seems to be working

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Linux and Fedora 22 does indeed support HDMI audio out using an AMD R9 270x GPU. The problem with the audio output solved itself by upgrading to a newer kernel. After the upgrade to kernel 4.0.5 it seems to work as it should.

UPDATE: I was a bit premature when setting this to solved. The problem did not disappear as I discovered that an ALSA rate converter was enabled. When I disabled the rate converter, the problem returned.

This bug report is the same problem I have. My temporary fix is to enable dmix (I had to because Steam hogs my audio device even when muted, so I thought this was the best solution).

The problem "disappears" when I enable dmix and a set rate. Maybe the current driver has a handshake problem? Bitstreaming does not work, so I'll have to disable passthrough in Kodi

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From what I have read, the most recent AMD R9 270x drivers for Linux do not support HDMI audio. Unless you write your own drivers, I don't think this will be possible until a future update arrives. I suggest using your motherboards sound in, as the built in audio in the R9 series of GPUs is meh. You can buy an HDMI sound splitter here. If you search around, you might be able to find a cheaper one.

  • Hmm... So PulseAudio is the way to go? I suppose it handles the communication with ALSA in a much better way than I'm currently able to. When using PulseAudio, the HDMI audio output from the 270x-card works. Even though it is not able to bitstream HD audio formats. – HJahre Jun 5 '15 at 22:32
  • I agree. If you are truly that worried about audio quality, though, I recommend getting a dedicated sound card. – Firepower0701 Jun 5 '15 at 23:30
  • Also, why does your media center have a 270x? – Firepower0701 Jun 5 '15 at 23:31
  • The reason for having a 270x is that the media center was my primary gaming rig when I had Windows installed. I have wanted a Linux based media center for some time, and as more and more games gets Linux-ports I thought I could try to install Linux on my media center. I don't think sound quality is an issue because I have connected the media center to my surround receiver. As I understand, it is the receiver DAC which is used as HDMI is a digital interface – HJahre Jun 5 '15 at 23:44
  • That makes sense. I was thinking that the 270x was overkill. – Firepower0701 Jun 5 '15 at 23:49

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