From mboxrd@z Thu Jan 1 00:00:00 1970 From: Clemens Ladisch Subject: Re: Direct Stream Digital (DSD/DST, One Bit Audio) HDMI pass-trough Date: Wed, 15 Oct 2014 11:41:58 +0200 Message-ID: <543E4166.7050704@ladisch.de> References: <543C58AC.9000701@linux.intel.com> <543D369E.5020002@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from dehamd003.servertools24.de (dehamd003.servertools24.de [31.47.254.18]) by alsa0.perex.cz (Postfix) with ESMTP id 530B426051C for ; Wed, 15 Oct 2014 11:41:59 +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 , Pierre-Louis Bossart Cc: alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org Andrej Falout wrote: > 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. Because they just need to copy the packets from the input to the output. > Can you please point out a specification or other document that say > otherwise? For PCs, all HDMI outputs are handled with HDA controllers. The HDA specification does not mention DSD. AMD's HDA verb documentation has the following list of audio formats codes: 0: reserved 1: LPCM 2: AC-3 3: MPEG1 (Layers 1 and 2) 4: MP3 (MPEG1 Layer 3) 5: MPEG2 (Multichannel) 6: AAC 7: DTS 8: ATRAC 9: Reserved 10: Dolby Digital + 11: DTS-HD 12: MAT/MLP (Dolby True HD) 13: Reserved 14: WMA Pro Would DSD be one of the reserved ones? > As you say, these are rather straightforward to implement ... if one bothers to implement it. > Same specification also described DSD stream setup, which is is > essence exactly the same, just uses the different identifiers. So the hardware needs some mechanism to output these identifiers. >> 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 That page lists the version where a feature was introduced; these are not requirements. The HDMI specification says: | If an HDMI Source supports any HDMI audio transmission, then it shall | support 2 channel L-PCM ..., with either 32kHz, 44.1kHz or 48kHz | sampling rate and a sample size of 16 bits or more. [...] | An HDMI Sink that is capable of accepting any audio format is required | to accept two channel ... L-PCM audio at sample rates of 32kHz, | 44.1kHz, and 48kHz. Regards, Clemens