On Mon, Jul 28, 2003 at 01:33:43PM +0100, James Courtier-Dutton wrote: > You are correct, SPDIF and alsa does NOT work with all cards and all > receivers. > Points to note: - > 1) Does the receiver require "non-audio" bit to be set? Some do, some > don't. My receiver does need it.
Yes, unfortunately it does!!! > 2) Does the sound card set the "non-audio" bit correctly when outputting > AC3 data. The SB Live does this correctly. I think the cs46xx and the intel-8x0 don't (like my DVB card). > 3) Does the sound card output data un-modified from the PC to the SPDIF > socket. The SB Live does interpolation on the PCM samples from the PC, > so that the samples comming out of the SPDIF are different from the PCM > samples from the PC. This therefore corrupts the AC3 frame (crc checks > are done on it by the receiver) and no sound is output. (Normal stereo > sound works because the ear cannot tell the difference between > interpolated samples and the original samples). The alsa programmers > have done a special work around for the SB Live problem, using something > called the TRAM, in order to bypass the interpolators and get perfect > AC3 output. So, maybe I should consider using a SBlive (and buy a "good" cable for it)!!! > 4) Sample rates. Some audio cards can only work at 48Khz, or only at > 44.1Khz, so outputting an AC3 signal from a DVD requires 48Khz, but > outputting a AC3 signal from a CD requires 44.1khz. So, depending on > where the media file with AC3 in it came from, it may or may not play. I am not sure of the sample rate that come from the DVB source? > It seems that SPDIF AC3 output is about the last feature that the alsa > developers add when a new card is supported with alsa. > As intel8x0 is used on so many different motherboards, alsa cannot hope > to support them all. The important issue with intel8x0 is the type of > ac97 chip used. If you run alsamixer, in the top left corner, it will > have "Chip: ....". Which chip does you motherboard have. I am not at home now, but according to http://www.msi.com.tw/program/products/mainboard/mbd/pro_mbd_detail.php?UID=311&MODEL=MS-6398E I have a Realtek ALC650 6-channel audio > All motherboards use different chips, and it is the programming of that > chip that is required in order to set the "non-audio" bits. > Summary: - > Your problems are most likely to be (2) and (4). I think (2) is the real one, because, a friend with the same Digifire 7.1 card and another receiver have perfekt 5.1 sound with his receiver. Is there any hope for it to be solved? It's not a real problem for me to use the SBlive or the Digifire 7.1 as I don't really need the Firewire of the Digifire 7.1 ;-) Thank you very much, Grégoire __________________________________________________________________ http://www-ima.unil.ch/greg ICQ:16624071 mailto:[EMAIL PROTECTED] ------------------------------------------------------- This SF.Net email sponsored by: Free pre-built ASP.NET sites including Data Reports, E-commerce, Portals, and Forums are available now. Download today and enter to win an XBOX or Visual Studio .NET. http://aspnet.click-url.com/go/psa00100003ave/direct;at.aspnet_072303_01/01 _______________________________________________ Alsa-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/alsa-devel
