On 11/14/13 15:04, Antti Palosaari wrote: > Hello > Should I feed whole raw USB packet to libv4lconvert or rip headers > off inside Kernel and feed only data? It is very trivial to remove > headers in kernel and in a case of USB it does not even cost about > nothing as you have to mem copy data out from URB in any case (if you > do it on that phase). > > Lets take a most complex case I have. There is not only raw data, but > some meta-data to process samples. In that case those samples are > bit-shifted according to control bits in order to increase nominal > sample resolution from 10 to 12 bits (not sure if it is bit shift or > some other algo, but shifting bits sounds reasonable and testing > against RF-signal generator results looked correct as it is now > implemented). > > So do I feed that whole USB packet to userspace or do I have to > remove headers + do bit bit shifting and forward only raw samples to > userspace? I would definitely remove headers and any garbage but pass the rest to userspace as-is. There is quite a bit of conversion code in the example you pointed to, more than I feel belongs in the kernel, so moving that out to userspace makes sense IMHO. Regards, Hans > > > That example could be found from: > drivers/staging/media/msi3101/sdr-msi3101.c > > Here is what on USB packet looks like: > > +=============================================================== > | 00-1023 | USB packet type '384' > +=============================================================== > | 00- 03 | sequence number of first sample in that USB packet > +--------------------------------------------------------------- > | 04- 15 | garbage > +--------------------------------------------------------------- > | 16- 175 | samples > +--------------------------------------------------------------- > | 176- 179 | control bits for previous samples > +--------------------------------------------------------------- > | 180- 339 | samples > +--------------------------------------------------------------- > | 340- 343 | control bits for previous samples > +--------------------------------------------------------------- > | 344- 503 | samples > +--------------------------------------------------------------- > | 504- 507 | control bits for previous samples > +--------------------------------------------------------------- > | 508- 667 | samples > +--------------------------------------------------------------- > | 668- 671 | control bits for previous samples > +--------------------------------------------------------------- > | 672- 831 | samples > +--------------------------------------------------------------- > | 832- 835 | control bits for previous samples > +--------------------------------------------------------------- > | 836- 995 | samples > +--------------------------------------------------------------- > | 996- 999 | control bits for previous samples > +--------------------------------------------------------------- > | 1000-1023 | garbage > +--------------------------------------------------------------- > > > regards > Antti > -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
