From mboxrd@z Thu Jan 1 00:00:00 1970 From: Manuel Jander Subject: Re: [Openvortex-dev] Re: au88x0 - Replace spdif frequency control by IEC958 control Date: Tue, 01 Mar 2005 11:09:42 -0300 Message-ID: <1109686182.3296.19.camel@localhost> References: <42246DB6.5040608@netvigator.com> Reply-To: mjander@users.sourceforge.net Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit In-Reply-To: <42246DB6.5040608@netvigator.com> Sender: alsa-devel-admin@lists.sourceforge.net Errors-To: alsa-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , List-Archive: To: Raymond , openvortex-dev , alsa-devel List-Id: alsa-devel@alsa-project.org Hi, On Tue, 2005-03-01 at 21:27 +0800, Raymond wrote: > >> The parameter 'spdif_mode' in the routine > >> vortex_spdif_init(vortex,spdif_sr,spdif_mode) in au88x0_core.c seems > >> to control AC3 passthrough. > >> > >> However the two memory mapped I/O VORTEX_SPDIF_CFG0 and > >> VORTEX_SPDIF_CFG1 seem to be write-only, return zero when read. > > >Then we need to cache the values. Just as we currently do with many other registers :) > Define snd_aes_iec958_t spdif_out in struct snd_vortex in au88x0.h > [snip!] > http://lists.gnu.org/archive/html/openvortex-dev/2003-11/msg00008.html > > 3) Do we need to change the ADB routing when using AC3 passthrough ? Hmm, good question. Maybe yes, because the current SPDIF PCM device route does stereo deinterlacing (separating two stereo channels). The SPDIF interface has 2 input sinks. For AC3 data, 2 interlaced channels does not make ant sense, because it could be 4, 6 or more, encoded in who knows what. Its just some raw data that must be passed through intact. It may be that in AC3 passthrough mode the SPDIF transmitter just re-joins the 2 data streams resulting in the original raw bit stream, hopefuly not messing it up. Maybe someone with more SPDIF knowledge can comment on this ? > > > > > 5) What additional kcontrol and routine are needed for SPDIF IN ? > > AFAIK, there is no direct SPDIF input interface on the au8830 chip. It looks like that the SPDIF input is implemented using a I2S port or one of the coporecessor interfaces. Since they are all sincronous serial interfaces, they probably are almost the same and almost compatible between each other, requiring little tweaking/additional circuitry on the interface daughter-board. > 5) How can STAC9721 stereo codec provide quad audio ? ( Is it through > SPDIF-I2S link ? ) That depends on the hardware. AFAIK, the STAC9721 supports only 2 channels. If we want 4, then obviously, the other two must go through any other codec. It could be a secondary STAC9721, a I2S codec connected to the I2S interface, some other kind of codec/DSP connected to any of the 8 coprocessor I/O interfaces, SPDIF, or whatever interfaces there might be we don't even know about. Best Regards -- Manuel Jander Electronic Engineer ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click