Clemens Ladisch wrote: > Florin Andrei wrote: >> [...] >> But with the PC, once the digital coaxial carrier comes up, it's always >> ProLogic and 2.1, never Dolby Digital and 5.1 > > SPDIF was designed for stereo, so it has only the bandwidth for two > channels of data at 48 kHz. (There are extensions for higher sample > rates by increasing the clock, but there are never more than two > channels.) > > To transport more than two channels over SPDIF, the audio data has to > be compressed so that it fits into the bandwidth that two uncompressed > channels would use. There are two common codecs, Dolby/AC-3 and DTS; > both are heavily patented. > > Any sound card that wants to encode multichannel audio for transport > over SPDIF has to include an encoder license. Very few do (the Windows > drivers for CMI8768+/8770/8788 and some X-Fi cards come with encoders). > Without encoder, 5.1 playback works only when the source data has > already been encoded previously (e.g., on a DVD). Awesome - that clarifies some things I discovered last night when googling around and doing experiments with the motherboard. The consensus seems to be it's very hard to do 5.1 over S/PDIF unless the data is already encoded like that (DVD) - you provided the explanation for that. So, if I play a DVD it might be doable, but if I play a game that has capabilities for 5.1 output, most likely it will not work. What I discovered is that the sound chip on the mobo can send 5 audio channels over analog. I guess that should remove all limitations, isn't it? > AFAIK there is no Linux distribution that ships with an encoder, > but you can download and install an AC-3 encoder manually (see > <http://www.alsa-project.org/main/index.php/A52_plugin>). Is there anything similar for Windows? Some sort of universal plugin that works with any card? -- Florin Andrei http://florin.myip.org/ _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
