Isochronous Urbs.

NTDEV
1

I receive isochronous urbs from usbaudio.sys which I process. The problem is that while the Offset field in the USBD_ISO_PACKET_DESCRIPTOR structure is initialized correctly, the Length field is not (the Length field is always 0). Has anyone else encountered this behavior?

Thanks,

Kevin.

2

xxxxx@gmail.com wrote:

I receive isochronous urbs from usbaudio.sys which I process. The problem is that while the Offset field in the USBD_ISO_PACKET_DESCRIPTOR structure is initialized correctly, the Length field is not (the Length field is always 0). Has anyone else encountered this behavior?

Yes, I have seen this as well… For an outgoing isochronous URB, you
are apparently supposed to assume that every packet is completely full.
This is not documented, and it’s not intuitive, but usbaudio.sys creates
'em that way, and the host controller accepts 'em.

–
Tim Roberts, xxxxx@probo.com
Providenza & Boekelheide, Inc.

3

Thanks Tim.

Kevin.