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USB Superspeed Peripherals

HuYa_4249091
Contributor

Hi, I’ve 2 questions for cyfxuvcdscr.c - CyFxUSBSSConfigDscr[ ]’s “class specific uncompressed VS frame” descriptor in AN75779 example.

VS frame descriptor.jpg

Q1: Min/Max bit rate bits/s field is NOT MATCH actual situation

According to the definition in UVC spec:

dwMinBitRate.JPG

However, I still don’t understand clearly. Does it means that the max/min range for the total bits per second?

Min/Max bit rate bits/s value: 0x31975000 = 832,000,000bps

1 frame bytes: 1280 * 720 * 2 = 1,843,200

Total bits in 30 frames: 1,843,200 * 8 * 30 = 442,368,000bps

832,000,000bps > 442,368,000bps: So the situation(720p, 2bytes for 1 pixel, 30fps) is still valid?

 

Q2: Maximum video or still frame size field is NOT MATCH actual situation

According to AN75779:

max image size in bytes.jpg

I found the field is correspond totally in High Speed’s descriptor(480p):

High speed descriptor: 0x00096000 = 614,400

Actual frame size: 640 * 480 * 2 = 614,400

However, in Super Speed descriptor(720p), the value isn’t match

Super speed descriptor: 0x001FA400 = 2,073,600

Actual frame size: 1280 * 720 * 2 = 1,843,200

2,073,600 > 1,843,200: So the situation is still valid? 

Any help will be highly appreciated!

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1 Solution
JayakrishnaT_76
Moderator
Moderator

Hello,

You can set the descriptor fields same as what you have calculated. That is:

Max and Min bit rates = 1280*720*16*30 = 0x1A5E0000

Max frame size = 1280*720*2 = 0x1C2000

It should work fine with the above settings.

Best Regards,
Jayakrishna

View solution in original post

1 Reply
JayakrishnaT_76
Moderator
Moderator

Hello,

You can set the descriptor fields same as what you have calculated. That is:

Max and Min bit rates = 1280*720*16*30 = 0x1A5E0000

Max frame size = 1280*720*2 = 0x1C2000

It should work fine with the above settings.

Best Regards,
Jayakrishna

View solution in original post