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USB Superspeed Peripherals

New Contributor

Hello guys.

My custom uvc device using fx3 has unstable fps problem.

Resolution is 1920 X 1080, frame rate is 30 (33ms).

I measured frame rate on windows, linux each.

Here is result.

  # My custom device on windows. ( frame rate is unstable. 25ms ~ 41ms )

clv200_window.jpeg

  # Microsoft HD CAM on windows. ( frame rate is stable. 31ms ~ 33ms )

webcam_window.jpeg

   and linux

    # My custom device on linux. ( also frame rate is unstable. 28ms ~ 37ms )

clv200_linu.jpeg

   # Microsoft HD CAM on linux. ( also frame rate is stable. 32ms ~ 36ms )

webcam_linu.jpeg

I used my custom firmware based on AN75779 example.

I exactly set frame size & frame rate & dma buffer etc... I think every value is right.

I attached my custom firmware code.

I want to know causes of problem.

What should I fix ???

How to resolve this ???

I really need your help !!!

Thank you !!!

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1 Solution
Moderator
Moderator

Hi,

Backflow/ Invalid sequence error/ commit buffer failure - all of these point to the same error. Occurrence of this error reduces the frame rate.

Can you please confirm if this error occurs with your firmware?

Please try increasing the horizontal blanking (while maintaining vertical blanking >500us)

Regards,

Hemanth

Hemanth

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3 Replies
Moderator
Moderator

Hello,

From test results, it seems like the sensor output is varying. To confirm it please probe the Frame Valid and Line Valid signals and share the traces.

Note: We would like to know the total time of a frame (V_Active + V_Blanking) so please share the trace such that the measurements are seen.

Also, let us know if you are able  to stream the video on both Linux and Windows

Regards,

Rashi

Regards,
Rashi
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New Contributor

RashiV_61

Thank you for reply !

Here is signal from scope.

# V Total ( 33ms )

20200810_132714.jpg

# V Blank ( 3ms )

20200810_132825.jpg

# V Active ( 30ms )

20200810_132753.jpg

I think signal seems right.

And It can able to stream on linux and windows both.

Problem is that frame rate is unstable, and also frame rate is up to 80ms very momently.

I want to know why and how to fix this.

Is it possible backflow causes the problem?

I fixed backflow by up buffer size latly.

But I don't think this causes the problem.

What should I test for this problem???

Thank you !

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Moderator
Moderator

Hi,

Backflow/ Invalid sequence error/ commit buffer failure - all of these point to the same error. Occurrence of this error reduces the frame rate.

Can you please confirm if this error occurs with your firmware?

Please try increasing the horizontal blanking (while maintaining vertical blanking >500us)

Regards,

Hemanth

Hemanth

View solution in original post

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