Hi Belá
As you know I very interested in the audio part of raspberry and microcore, so therefore my focus might be too narrow.
However, some of the interesting changes are:
Firmware: https://github.com/raspberrypi/linux/issues/320 . this issue describes crackling noise in the HDMI output, but also via an USB_DAC. This is a problem often encountered when using raspberry and an external USB-DAC. However, this was added to the firmware 2 days ago.
Kernel: The I2S connection is very interesting for an audio player build on the raspberry - for the exact reasons mentioned above. By using I2S we don't see the same cracks and pops in the audio as we see using USB-DACs.
The current kernel in microcore supports the HiFiBerry I2S DAC (and also other DACs) with great results. But the new kernel 3.12.9 supports a pure digital I2S HiFiBerry card
http://www.hifiberry.com/hbdigi which will give our raspberry a digital audio output.
https://github.com/raspberrypi/linux/commit/a76cc555cbac2a2136a7a0b4078381704a57d59dBy the way I'm not in any way connected with the company selling HiFiBerry audio cards, I just like the cards, and they are at the moment the only available I2S audio cards for our raspberry.
I would like to support the addition of digital out (S/PDIF or Toslink) in the piCorePlayer, therefore I had started building the newer kernel for microcore, but then I read this thread and thought that you might be working on the same.
Steen