Hello, On Wednesday 03 March 2010 17:01:39 Ujfalusi Peter (Nokia-D/Tampere) wrote: > On Wednesday 03 March 2010 16:18:42 ext Jarkko Nikula wrote: > > On Wed, 3 Mar 2010 12:02:48 +0200 > > > > Peter Ujfalusi <peter.ujfalusi@xxxxxxxxx> wrote: > > > The command for test: > > > aplay -fdat -d 1 /dev/urandom > > > > I recommend to use /dev/zero instead since urandom takes CPU time. > > > > > [ 96.290924] XBUFFSTAT: 0 > > > [ 96.293487] XBUFFSTAT: 0 > > > [ 96.296020] XBUFFSTAT: 0 > > > [ 96.299774] XBUFFSTAT: 1 > > > > > > So the buffer is kept full in element mode, as it is expected. > > > > I was expecting to see more variations. IRCC, the DMA in OMAP is doing > > transfers over the memory bus using some small bursts but I'm not > > completely sure. I'm thinking if that could explain the Eero's and > > Liam's observations? > > I kind of expecting similar result (this). > In element mode the threshold value is 0 (1 word). > So if one word is free in McBSP buffer, than it will assert the DMA request > line, and the DMA will write one word to McBSP. > So in theory the buffer must be kept full in this mode, with quite minimal > variation. > But I might be wrong on this... Well, to be precise, I expected that the XBUFFSTAT would have been 1 most of the time, and not 0. But in stereo we are still within one sample accuracy, so I think this is OK. -- Péter _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
