isochronous transfer packet is out of sequence

[Hans Petter Selasky]

On Tuesday 13 November 2012 16:23:06 SAITOU Toshihide wrote:
> In message: <201211131452.16508.hselasky at c2i.net>
> 
>             Hans Petter Selasky <hselasky at c2i.net> writes:
> > On Tuesday 13 November 2012 14:26:52 SAITOU Toshihide wrote:
> >> In message: <201211121342.47141.hselasky at c2i.net>
> >> 
> >>             Hans Petter Selasky <hselasky at c2i.net> writes:
> >> > On Monday 12 November 2012 12:52:08 SAITOU Toshihide wrote:
> >> >> 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.
> >> >> 
> >> >> 

Hi,

There are some internal limits, maybe not visible directly at libusb level.

The host hardware usually does not handle more than 128 milliseconds of 
transfers at a time.

You should not sumbit more frames than will be processed in (128 - 16) / 2 ms 
at any time. For HighSpeed with fastest interval you will need around 8*2*56 
ms worth of frames, which is the maximum supported.

grep -r USB_MAX_FS_ISOC_FRAMES_PER_XFER /usr/include
grep -r USB_MAX_HS_ISOC_FRAMES_PER_XFER /usr/include

Webcamd has patches for the Linux code, to fix this issue.

--HPS