Re: USB camera: ISO transfer ASAP?

"Pamela" <zhong_ping1971@xxxxxxxxxxxx> wrote:

I have a question on developing device driver for a USB2.0 camera. Now
a usb2.0 webcam is devloped based on USB camera minidriver library
(USBCAMD) in the DDK. This camera uses iso pipe to transfer the video
stream data.

Now the driver can preview the image, but the image is not stable, it
seems that some data are missing during transfer. From the data from
USB bus analyzer, the driver cannot provide the ISO request every
microframe so the FIFO is overflow and some data are discarded.

You have to provide buffers that are large enough to handle the whole USB
frame. If your ISO transfers every microframe, you'll have to provide
buffers with a multiple of 8 packets. How many packets are you providing?
--
- Tim Roberts, timr@xxxxxxxxx
Providenza & Boekelheide, Inc.
.

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