two data packet,I find that when do preview there is only one
Transfer on
Windows XP,
and there are many Transfers on Mac OS X and one Transfer has many
Transactions,the most
important thing is that the packet serial number is not
continuous,Could you
tell me
why is it, and how can I do to decrease latency and increase FPS
when doing
preview.
I'm sorry, but I don't fully understand this paragraph.
Are you submitting more than one ReadIsochPipeAsync() at a time? You
should. Since you say you have a high speed device, you need to
schedule your transfer for n microframes, starting at frame number
x. In our Video Class driver, I usually schedule 1 video frame worth
of requests. For example, if your frame rate is 30 frames per
second, I schedule 33 ms worth of data. For high speed, that means
that my frame list size is 264 (33 * 8). I then have a tunable
number of concurrent frames outstanding, each starting at ( n / 8 )
from the previous one, since the ReadIsochPipeAsync() requires a
starting USB Bus Frame Number, not a microframe number. At the back
end, I have another tunable # of buffers which I fill with the video
data. This allows me to give video data to the client and not have
to wait for them to release the buffer before I can fill it up again.
It would be a lot easier for you if you had a Video Class compliant
device.
HTH,
--
Fernando Urbina
USB Technology Team
Apple Computer, Inc.
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Usb mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/usb/email@hidden
