Hey, Any thoughts or pointers on what to look for in order to use different sample format between actual I2S and DMA? Thank you, Giedrius. On Thu, Dec 29, 2016 at 4:32 PM, Giedrius Trainavičius < giedrius.trainavicius@xxxxxxxxx> wrote: > The I2S and DMA format asymmetry sounds like what I'd be after. Do you > have any pointers for APIs / keywords to look around for in the code to see > how this should be set up? Is such format conversion supposed to be > happening in hardware itself, or the CPU when accessing the DMA buffer has > the chance to do the conversion? > > The relevant documentation and code I found so far would be: > > https://www.raspberrypi.org/documentation/hardware/raspberry > pi/bcm2835/BCM2835-ARM-Peripherals.pdf > https://github.com/raspberrypi/linux/blob/rpi-4.4.y/sound/ > soc/bcm/bcm2835-i2s.c > > I can't locate any relevant bits of code or information that'd indicate > capabilities of sample format conversion... > > Thank you, > Giedrius. > > On Thu, Dec 29, 2016 at 7:53 AM, Clemens Ladisch <clemens@xxxxxxxxxx> > wrote: > >> Giedrius Trainavičius wrote: >> >It uses I2S for sending / receiving audio. However, the master clock on >> our >> >sound card is generated by the ADC, which supports only 24 bit data, so >> >getting other sample formats is not possible. >> >> The I2S sample format need not be the same as what the DMA >> controller reads/writes from/to memory. >> >> >A question on 'plug' - it accepts 'nearest' as the argument for format, >> >rate, what happens in case the slave pcm stream supports the exact same >> >format as requested by user software? >> >> The plug plugin instantiates the actual conversion plugins only >> as needed; with no conversion, it vanishes entirely. >> >> >> Regards, >> Clemens >> >> > _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
