Hello Arai san,
The H blanking period and V blanking period can be calculated if we have the H Blanking (in pixels) and V Blanking (in lines) or if we have the V Total (in lines) and H Total (in pixels) of the sensor.
Please contact the sensor vendor for the H blanking (pixels) / H Total (in pixels) and V Blanking (in lines)/ V Total (in lines) settings for the given (1280*720 ) resolution. After getting those values, the sensor is configured with those values to get the desired video stream.
Please refer to this KBA Analysis of CX3 Video Timing Parameters – KBA226779 for the calculations of video timing parameter