2008/2/19, Clemens Ladisch <clemens@xxxxxxxxxx>: > Ignacy Kasperowicz wrote: > >> Just write the data to the device. > > > > Ok, but when I just write data to the device I don't really know how > > long it'll be playing. > > But you know how many sample you are writing, and you know the sample > rate. > > > There is no problem when I've infinite loop with writei inside. but I > > need to change freq of my sound signal with exact 843 us period time. > > Assuming a sample rate of 48 kHz, 1/1200 s corresponds to exactly > 40 samples. At 44.1 kHz, this would be 36.75 samples, so you'd have to > use groups of 37+37+37+36 samples with appropriate phase shifting. > > BTW: 1 / 1200 Hz = 833.33... µs > > > HTH > Clemens > Thanks for correction, I was trying to make this too complicated :P I dunno why I even thought about just setting how many samples to write in writei() :P Although, when from calculations indeed I should set 40 samples to get sine played for 1/1200Hz, in my code I need to set frames size value for 400. Do You know why? I have 48kHz rate, one channel and 16 bit PCM. >From what I've read there: https://bugtrack.alsa-project.org/wiki/wikka.php?wakka=FramesPeriods , "A frame is equivalent of one sample being played" so why I need multiply calculation result by 10 ? I think this is a last rookie question :) Thanks for answers :) ignacy PS. Yeah I know its 833.33...us, I've just rounded it up for experimenting ;) -- ################################################ gry świetlicowe drogą do wyższej fazy przemian. gg:681548 jid: fik@xxxxxxxxx usecide.net ################################################ _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
