Calculating MF_MT_AVG_BITRATE attribute

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video

Hi,
I am using H.264 codec to create MP4 file from images. IMFSinkWriter is used for encoding purpose.
While encoding, I need to control the quality of the encoded video by adjusting the average bit rate parameter value. But I could not get any equation for calculating this.
I tried several equations, but the video behavior is different for different type(resolution) of images.
One of the equation used is Frame width * Frame height * frame rate * Image quality parameter * some constant.
But this is not working for all types of resolutions.
My image quality parameter will be varied from 1 to 100.(Low to High)
Could you please provide an equation to calculate the average bit rate for controlling the image quality from Frame width, Frame height and frame rate?

I tried the VBR encoding but it does not work for the encoding using Sink writer.