[alsa-devel] USB asynchronous mode feedback format

Alex Lee lee188 at singnet.com.sg
Fri Oct 15 15:31:50 CEST 2010

On Fri, 2010-10-15 at 15:04 +0200, Julian Scheel wrote:

> Ah right, thanks.
> Well now I swapped data[1] and data[2]. When monitoring the amount of data I 
> get per read, it is constant at 192bytes, which would be expected for feedback 
> ratio of 48, right? But if I have 0x06 to 0x07 for example I do still get 
> exactly 192bytes per read, shouldn't I get less data in that case? (I always 
> try to read up to MAXPACKETSIZE which is 512, btw)


(1) The feedback rate has to fall withing +/- 10% of the nominal rate.
Otherwise it is ignored.

(2) You need to find out exactly how many samples the host sends you.
Look at my sdr-widget code, for example.  Then you read what the host
sends you.

(3) Do a > dmesg | tail 
    after unplugging and plugging your USB device in.  Then you can see
whether there are any errors in your syncpipe

btw, what is your Linux kernel version?


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