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Question regarding V4L2 Capture Application in DM8168 EVM.

Jongpil Won
Intellectual 595 points

I verified that saLoopback and saLoopbackScale application is working.

I want to capture two images via one input port. Then one is full-size image and the other is pre-view size image using scaling down.

Is it possible?

Or in saLoopbackScale application, can I get the full size image and resized images at the same time?

Best regards,

Jongpil

 

  • 0
    TI__Mastermind 20245 points

    Hi,

    Hardware supports this functionalityv but because of V4L2 framework limitation we are not supporting it. You can use VFPC components to do downscaling on captured image. This is supported using openMax VFCC component.

    Regards,

    Hardik Shah

  • 0 in reply to HardikShah
    Genius 3120 points

    Hi,

    We also have similar kind of requirement. If I understand correctly, what you are saying is e.g. capture 720P image using V4l2, store that image in some intermediate buffer (for other processing, it can be display or streaming) and give the V4l2 captured buffer to VFPC component for downscaling. According to my understanding this will introduce a memcpy in between which can affect the performance on ARM side. Is there any better way to get this done?

    This is very common feature (PIP) that many of us would like to have in VC kind of applications.

    Also, what is the limitation in the V4L2 framework to get two buffer (one full image [eg. 720P] and other downscaled image [eg D1/CIF] )?

    Regards,

    Krunal

  • 0 in reply to HardikShah
    Intellectual 595 points

    Hi, Thanks for your response.

    For my clearance, I'll put some more question in line.

    Hardware supports this functionalityv but because of V4L2 framework limitation we are not supporting it. You can use VFPC components to do downscaling on captured image. This is supported using openMax VFCC component.

    Q. Did you mean that I can't capture two image at one video input port using v4l2 framework?

    Q. In saLoopbackScale application, I understand that to downscaling from 1280*720 to 720*480, 

          first capture full size image and crop full size(1280*720). After that, resized image is displayed. Is it wrong?

         Is there any way to get full size image data and resized image data at the same time using v4l2? (the same reason for V4L2 framework limitation?)

     

    Regards,

    Jongpil

       

     

  • 0 in reply to Jongpil Won
    TI__Mastermind 20245 points

    Hi,

    Answers inline

    Jongpil Won said:
    Did you mean that I can't capture two image at one video input port using v4l2 framework?

    Yes,

    Jongpil Won said:

    Q. In saLoopbackScale application, I understand that to downscaling from 1280*720 to 720*480, 

          first capture full size image and crop full size(1280*720). After that, resized image is displayed. Is it wrong?

    You are right, but it can give only one output either full size or scaled. It cant give you both outputs.

    Jongpil Won said:
    Is there any way to get full size image data and resized image data at the same time using v4l2? (the same reason for V4L2 framework limitation?)

    Correct, Its V4l2 framework limitation.

    Regards,

    Hardik Shah