On 10/11/14, 1:33 AM, Andrej Falout wrote:
Hello,
I am collecting requirements for implementation a DSD HDMI pass-trough, according to HDMI specs version 1.2 and 1.3a
I am wondering if anyone previously worked on this, or has any interest in this functionality.
Any advice or pointers are gratefully received. Here is my list of the core facts so far:
1. hda_eld.c in current kernel git ignores raw DSD (One Bit Audio) labelled AUDIO_CODING_TYPE_SACD ("SACD" because originally DSD formats where only used commercially in SACDs) and compressed DSD (DST) is labelled AUDIO_CODING_TYPE_DST (1) 2. It is my understanding that apart from "special handling" denoted in "Table 47 CEA Short Audio Descriptor for Audio Format Codes 9 to 13", (eg setting the format code, etc) this should be a reasonably straightforward stream pass-trough (2) 3. Typical use scenario for DSD over HDMI: an DVD/BluRay player that supports SACD (Super Audio CD) outputs a DSD stream over HDMI to a DSD capable receiver. For instance, my Oppo and Sony BluRay players both do that, and all my receivers (Onkyo, Pioneer, Marantz, Yamaha, NAD) have DSD DACs and I can play both stereo and surround music this way, without converting DSD to PCM. There is currently about 30 million DSD capable receivers on the planet, conservatively speaking (Just Onkyo makes 1 million a year, and makes DSD capable ones since 2003) 4. Wanted scenario: play DSD files using DSD enabled players (Linux: MPD, mplayer, VLC, Squeezeboxserver, etc / Windows: FooBar, JRiver, etc) to an HDMI audio card/device on a PC motherboard or add-on video card with HDMI, connected via HDMI cable to a DSD enabled receiver/DAC 5. Note that as far as I know, no proprietary drivers on Windows (ATI/AMD, Nvidia, Intel) support this; It will be the first time a device that is not a SACD player outputs DSD over HDMI, on any OS. I am assuming that this has nothing to do with hardware limitations of the HDMI chips used for video outputs (I could not find any reference for such assumption in any HDMI chips I examined specs for). Therefore, I assume that implementing this has no hardware prerequisites.
HDMI controllers typically don't support DSD in the PC space. It'd be easier to convert to high-res PCM (HBR).
6. DSD format general info: http://en.wikipedia.org/wiki/Direct_Stream_Digital http://dsd-guide.com/ http://dsd-guide.com/what-dsd-audio-simple-explanationThanks, Andrej Falout
References: (1) https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/sound/p...
- Same source file in Alsa GIT tree:
http://git.alsa-project.org/?p=alsa-kernel.git;a=blob;f=sound/pci/hda/hda_el...
(2) CEA Standard PDF, page 66, table 47. HDMI specs version 1.3a, pages 72-73 for DSD(One Bit Audio) and DST audio packet header and body formats
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