At Mon, 27 Oct 2008 20:08:04 +0000, James Courtier-Dutton wrote: > > Alexander E. Patrakov wrote: > > Takashi Iwai wrote: > > > >> Note: 44.1kHz is possible, but is more complex because it uses a method > >> whereby the channel ring marks each sample in the channel ring as valid > >> or not, so to get 44.1kHz, some samples are simply tagged invalid. The > >> "channel ring" is not the ring buffer that is used to get sound samples > >> to the card. The "channel ring" is used to pass samples between > >> different processing modules on the card. One of these processing > >> modules is the SRC, another is the INs/OUTs, another is the hardware > >> mixer, and yet another is the DSP. > > > > Do I understand correctly that the card internally resamples the sound > > to a different rate using the zero-order-hold method? If so, I'd rather > > not see this feature at all unless the "i_want_horrible_sound" parameter > > is passed, because software can do it better, and some program will > > surely default to using this hardware misfeature. > > > > > Alex, > > I added that comment (takashi cut and pasted my text). No resampling is > done. > Say you have a buffer that is running at 48kHz. > So you have say 480 samples at the 48kHz rate. > But if you want to transfer 44.1kHz rate samples over it, you only want > 441 samples to be there, so what to do with the left over 39 samples. > What the xfi does is next to each sample it adds a "valid" tag. > So, the xfi adds those 39 samples but marks them as "invalid". > The xfi then drops the 39 "invalid" samples, leaving only the 441 > "valid" samples just before sending them at 44.1kHz to the DAC. > Does this explain things a bit better. > FYI, the xfi actually works internally at 384kHz, so it is actually > marking a lot of samples as "invalid". Hm, so what is special about using 44.1kHz if many samples in the audio-ring are already marked as invalid even with 48kHz? It'd be helpful if you could provide a bit more information (or a pseudo-code) for supporting non-48/96kHz samples. thanks, Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
