[PD] PD support for new alsa

Winfried Ritsch ritsch at iem.kug.ac.at
Fri Apr 20 12:05:39 CEST 2001


 > This should work with the alsa cvs version as of a few days ago or the
 > newest beta available on the alsa website (www.alsa-project.org).  It is
 > currently limited to 16/24 bit interleaved cards - i.e. no hammerfall.  I
 > have only tested it on a stereo 16 bit card.  Either Winfried Ritsch or I
 > will produce an optimized version for the hammerfall soon (still
 > interested in doing this Winfried?).  Finally, you will probably
 > need to set the number of frags to make it work at all.  Try this
 > commandline first:

yes I am on the way, but the alsa-mmap interface was just changed
again the last days ;-(, even there is one problem, that is you cannot
allocate a subset of channels in mmap on alsa so always have to use
all 26 (18) channels, which is not always preferabel. Maybe we just
should integrate the non-interleaved no-mmap interface also in your
driver-interface or using "plugin:" for these cases and a special mmap
one for really low latency for all channels ?

One other idea is that the driver allocates all channels but fill only
these which are needed, so an performance improvement could be that
the adc~/dac~ object reports or are asked in some way if they are
allocated, so only these channels are copy/converted from/to float
to/from card-format.

 > I know this seems like a lot of fragments, but this is comprable latency
 > to OSS on my machine.  Please test this and tell me how it works or
 > doesn't work.  Miller, if you would like a diff just let me know.

ok, the option -noadc and -nodac does a:
pd: pcm_params.c:2081: snd_pcm_hw_refine: Assertion `pcm && params'

mfg winfried

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