From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pierre-Louis Bossart Subject: Re: Direct Stream Digital (DSD/DST, One Bit Audio) HDMI pass-trough Date: Wed, 15 Oct 2014 08:38:22 -0500 Message-ID: <543E78CE.8070801@linux.intel.com> References: <543C58AC.9000701@linux.intel.com> <543D369E.5020002@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by alsa0.perex.cz (Postfix) with ESMTP id 69B71260432 for ; Wed, 15 Oct 2014 15:38:34 +0200 (CEST) In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: Andrej Falout Cc: alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org On 10/14/14, 10:30 PM, Andrej Falout wrote: > Hello Pierre-Louis, > > On Wed, Oct 15, 2014 at 3:43 AM, Pierre-Louis Bossart > > wrote: > > On 10/13/14, 7:49 PM, Andrej Falout wrote: > > > What are you basing your assessment that "HDMI controllers typically > don't support DSD in the PC space"? I looked, but could not find any > evidence for this. > > > I am basing my judgement on first-hand experience with silicon. > > > Me too :) Absolutely every HDMI related chip I examined specs for and > tested, including the cheapest of the cheap ones made as HDMI repeaters > for splitters and audio extractors, supported DSD stream passing (Both > up and down stream), just as they did all other audio bitstreams. > > For example: > http://www.mds.com/system/resources/BAhbBlsHOgZmSSIuMjAxMy8xMC8xNi8xNy8yOS80NS80MjYvSFNSX0hTX3Jldl81ZC5wZGYGOgZFVA/HSR-HS_rev_5d.pdf > > Can you please point out a specification or other document that say > otherwise? You are not looking at the right specifications. You need to look at HDMI interfaces for PCs, and I maintain that most of them don't support DSD. > > > Certainly, DSD is not a part of HDMI hardware implementation > (such as > for example, CEC). From all info I have, DSD is simply > multiplexed into > HDMI data stream, just as DST-HD or AC3 is. > > > This multiplexing is typically not implemented - mainly because this > isn't a format used outside of niche markets > > > It seems that you are talking about coding/decoding, not bitstream > multiplexing? Same TMDS stream multiplexing is used for all audio > streams in HDMI - weather native (PCM/DSD) or encoded (AC3, DTS, ...) > The only real difference that I can see is the stream setup as described > in my OP ("Table 47 CEA Short Audio Descriptor for Audio Format Codes 9 > to 13", (eg setting the format code, bittness, etc)) > > and there was no real format to convey DSD over PCM frames until the > DOP format was created in 2012. > > > Again, I am talking about native DSD formats/streams, not DoP - which is > in essence PCM. HDMI specs do not know or need DoP. HDMI is capable of > native DSD transfer since version 1.2. See point #5 in my OP. > > DTS-HD and AC3 use a PCM format which is rather straightforward to > implement but there's quite a few cases where these modes have been > dropped. > > > As you say, these are rather straightforward to implement, as evident > from the HDMI specification which describes the stream setup. Same > specification also described DSD stream setup, which is is essence > exactly the same, just uses the different identifiers. (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) > > Can you point out a documented case where "these modes have been dropped"? > > HDMI only requires 48kHz 2ch really. > > > Even the HDMI version 1 requires "8 channel LPCM > , 192 kHz > , 24-bit audio capability" : > http://en.wikipedia.org/wiki/HDMI#Version_comparison Wrong. See the HDMI spec, not Wikipedia. The only requirement is: If an HDMI Source supports any HDMI audio transmission, then it shall support 2 channel L-PCM (using an IEC 60958 Subpacket structure), with either 32kHz, 44.1kHz or 48kHz sampling rate and a sample size of 16 bits or more. Additional rates are not required and often not implemented: An HDMI Source is permitted to transmit L-PCM audio data at sample rates of 32kHz, 44.1kHz,48kHz, 88.2kHz, 96kHz, 176.4kHz or 192kHz. DSD is equally optional: A Source may transmit One Bit Audio at an fS (1/64th of the bit rate) of 32kHz, 44.1kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz or 192kHz. Any Source capable of supporting One Bit Audio should support an fS of 44.1kHz, corresponding to a bit rate of 2.8224MHz. May and should are not mandatory statements. > > Note that the facts don't mean any negative judgement on quality, i > was at AES this week-end where I heard outstanding DSD/DXD > recordings. You will have more luck with a USB DAC, there are > multiple USB DSD products available. > > > There is about 30 million DSD capable DACs in the world today, > conservatively speaking, most of them multi-channel capable (See point > #3 in my OP). I appreciate that there are a few USB DSD DACs out there > too, and even 2 (two) multi-channel models. ;) I wish you luck. over and out. > Thanks, > Andrej Falout > >