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Some questions regarding V4L2 application.

Jongpil Won
Intellectual 595 points


Hi, I have several questions for my clearly understanding.

I'm using saLoopback application for our test with DM8168 EVM board which has VC daughter board.

1. There are 3 sample application using v4l2 driver.

1-1. What is the main difference saLoopback and saLoopbackFbdev?

        I want to know what is the main advantage and disadvantage of using V4L2 display driver and Fbdev display driver.

2. With 1080I resolution, Could I using saLoopback Fbdev? When I execute application, it says "1080I can not caputre RGB data". Why?

    Does it only support 720P or 1080P?

3. with saLoopback application, capture driver's output is YUV422 intereaved format. I want to seperate Y channel for our image processing,

    I use C6accel dsp library. (especially, Vision library.)  In vision library, there are several conversion funtion.

    I used C6accel_VLIB_convertUYVYint_to_YUVpl(). Here is my question. My captured data format is YUYV but the naming of API is UYVY.

   I wonder that the API is working well? Or Should I change bit order for input data format to UYVY format?

4. I'm in process for NDA with TI. I'm about to get HDMI Receiver driver from TI. When it is completed, I'll use HDMI input instead of component input.

    4-1. What do I need to modify for using saLoopback or saLoopbackFbdev application?

    4.2. With HDMI input, Could I capture RGB data from HDMI? YCbCr is possible or Only YUV is supported via HDMI?

For your understanding, My scenario is below.

I want to capture data from Full HD camera with HDMI input.

I want to add some image processing like hand detection, body detection, face detection something like that.

With detection result, I want to add some effects like blur, remove some images. etc.

Most of image processing will be developed in DSP side.

Before developing algorithm in DSP, I want to check our conditions.

 

Regards,

Jongpil.

  • 0
    TI__Mastermind 20245 points

    Hi,

    Answers inline,

    Jongpil Won said:
    What is the main difference saLoopback and saLoopbackFbdev?

    Ans: saLoopback gives YUV422 to memory and displays that through V4L2 display driver. saLoopBackFbdev gives out RGB to memory and displays it though FBDEV.

    Jongpil Won said:
    want to know what is the main advantage and disadvantage of using V4L2 display driver and Fbdev display driver.

    Ans: Over what. With what are you comparing V4L2 display and Fbdev driver.

    Jongpil Won said:
    With 1080I resolution, Could I using saLoopback Fbdev? When I execute application, it says "1080I can not caputre RGB data". Why?

    Ans: YUV to RGB conversion is only possible for progressive formats. This is a hardware limitation.

    Jongpil Won said:
    with saLoopback application, capture driver's output is YUV422 intereaved format. I want to seperate Y channel for our image processing,

    Ans: Capture driver can give YUV420 semiplanar output. It can also give YUV422 semiplanar output. In semiplanar format you will directly get Y in separate plane.

    Jongpil Won said:
    I'm in process for NDA with TI. I'm about to get HDMI Receiver driver from TI. When it is completed, I'll use HDMI input instead of component input.

    Ans: HDMI can capture both YUV and RGB. You will need to develop HDMI driver sub-device driver and attach it to V4L2 capture driver. 

    Regards,

    Hardik Shah