I have tryed the USB isochronous transfer for UVC cam using libusb
interface and I find the packet fragment is out of sequence on the
FreeBSD(1). But I don't find it on the MacBook(2).
(1) FreeBSD 9.1-RC2, Intel Core i7 3770T
(2) Mac OS X 10.6.8, Intel Core 2 Duo, libusb 1.0.9 (single core)
Can I prevent this behaviour using libusb interface or is
this an expected behaviour?
The bellow I issued two libusb_submit_transfer at the beginning.
----- log (1)
049 4437e06b 0 c 818
04a 4437e06b 0 c c00
04b 4437e06b 0 c 818
UVC_STREAM_EOF
total a1400
04c 4402516b 1 c b9c
04d 4402516b 1 c 87c
04e 4402516b 1 c 800
04f 4402516b 1 c c00
050 4402516b 1 c 800
051 4437e06b 0 c c00
052 4437e06b 0 c 744
053 4437e06b 0 c c00
----- callback function
static void cb(struct libusb_transfer *xfer)
{
uint8_t *p;
int plen;
int i;
p = xfer->buffer;
for (i = 0; i < xfer->num_iso_packets; i++, p += PKT_LEN)
{
if (xfer->iso_packet_desc[i].status ==
LIBUSB_TRANSFER_COMPLETED)
{
plen = xfer->iso_packet_desc[i].actual_length;
if (plen < 2)
continue;
if (p[1] & UVC_STREAM_ERR) // bmHeaderInfo
continue;
fprintf(stderr, "%03x ", i);
fprintf(stderr, "%08x ", p[2] | p[3]<<8 | p[4]<<16 |
p[5]<<24); // pts
fprintf(stderr, "%01x ", p[1] & UVC_STREAM_FID); // fid
fprintf(stderr, "%01x ", p[0]); // header length
fprintf(stderr, "%x\n", plen); // actual length
total += plen - p[0];
if (p[1] & UVC_STREAM_EOF)
{
fprintf(stderr, "UVC_STREAM_EOF\n", total);
fprintf(stderr, "total %x\n", total);
if (total < FrameSize)
{
fprintf(stderr, "insufficient frame
data.\n");
write(fd, padding, FrameSize - total);
// zero padding
}
total = 0;
}
write(fd, p + p[0], plen - p[0]); // write payload data
}
}
if (libusb_submit_transfer(xfer) != 0)
{
fprintf(stderr, "submit transfer failed.\n");
}
}
---
SAITOU Toshihide
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