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Hello,
I am not sure whether alsa-devel is the right place for this kind of question. If it is not, please tell me a better place for them.
I am building my kernel against the drm-tip freedesktop repository which includes the patches from December 2016 (message id 1480992519-108079-1-git-send-email-libin.yang@intel.com and follow-ups on alsa-devel). I am using a ThinkPad X250 and the ThinkPad Ultra Dock with the HDMI output connected to my YAMAHA HTR-2866; this hdmi output is seen as display port and uses DP MST from the dock.
In principle, everything is working quite well; however, I frequently recognize two weird behaviours:
* First of all, my audio receiver has 5.1 support. When I configure my laptop to send 5.1 audio using alsa or pulseaudio, there is only silence and no audio signal reaches the receiver; however, when I choose 7.1 digital surround (which my receiver actually does not suppo rt natively), everything works well and the two additional speakers are split to the existing ones (I do not know whether alsa/the kernel or the receiver does this, probably it is the receiver). This problem is pretty much only esthetical, as everything works fine if I use the 7.1 "work-around" (Digital Stereo does work also, but obviously does not support the full 5.1 setup) * The other problem -- which is actually very annoying -- is that there frequently is silence though there is audio playing; this happens now and then, but when there has been *no* output for a while, it always happens a few seconds after starting the new output and lasts for two to three seconds. During these periods of silence, the icons on my receiver indicating that there is an audio source are also gone. This problem occurs with 7.1 configuration as well as with Digital Stereo.
I am not sure what these problems are caused by and do not know what kin d of debug information you may require to get more hints on how to solve them. Any hints are appreciated.
Thank you for your advice, Pascal Wichmann