On Tue, Jun 9, 2009 at 5:39 PM, Eric Miao <eric.y.miao@xxxxxxxxx> wrote:>>> 2009/6/9 Daniel Ribeiro <drwyrm@xxxxxxxxx>:> > Em Seg, 2009-06-08 às 19:06 +0100, Mark Brown escreveu:> >> Think about TDM mode for a minute here - there a separate configuration> >> for the sample size on the wire opens the way to using a lower sample> >> size in a given timeslot than the timeslot supports, reducing the need> >> for the CPU to rewrite data. Or to put it another way, I can't see TDM> >> mode working unless the sample size is constrained to always be exactly> >> that desired so it seems sensible to have a standard way of doing that.> >> > Hum... Now I understood this. If i want to use network mode with 2> > different codecs, and they differ on the expected frame_size i have to> > use the smaller frame_size for both codecs.> >> > And indeed, in this case the best place to setup the frame size would be> > on set_tdm_slot().> >> >> I'd rather come up with a cleaner way of configuring the magician case> >> that's explicit about what it's trying to achieve. It doesn't need to> >> be in user space, though.> >> > I dont know how to do this other than just changing the frame size... :)> >>> OK, not having enough time to read all this thread, let's make sure> first we are on the same floor:>> frame_width = number of bit clocks per frame> sample_width = number of bits per sample>> And the assumption that>> frame_width = sample_width * channel ( = LRCLK for I2S )>> is no longer (and ever) correct.>> E.g. the frame width could be 64fs, meaning a whole frame is consisting> of 64 bitclks - that's saying, sample width from 1 - 64 are possible, sorry for the HTML mail, and here is a typo: sample width should be within 1-32 > For typical 16-bit sample width I2S format, the envelope for each sample> is 32 bitclks, and offseting by 1 bitclk starts the 16-bit sample.>> And the TDM mode is actually special for PXA-SSP to emulate the I2S> protocol, it's no way generic TDM in a common sense. So talking about> set_tdm_slots(), I'd really like to hide into the format setting code> of I2S/Left_J to avoid further confusion.>> And I still didn't quite capture the issue of magician. Phillip, do> you have any HW reference to the audio codec and the connection on> magician? --Cheers- eric_______________________________________________Alsa-devel mailing listAlsa-devel@xxxxxxxxxxxxxxxxxxxx://mailman.alsa-project.org/mailman/listinfo/alsa-devel
