Why does the bitrate increase when movement is detected while using H.264 compression?

The increase in bitrate during movement detection when using H.264 compression is primarily associated with the behavior of P-frames. In video compression, P-frames (predictive frames) store only the information that is different from previous frames, rather than storing a complete image. However, when there is motion detected within the scene, the differences between consecutive frames become larger and more complex. This increased complexity in the image necessitates more data to accurately encode the differences, resulting in larger P-frames.

As a consequence of this increase in size, the overall bitrate rises because the larger P-frames require more bits to represent the motion and changes in detail, thereby consuming more data bandwidth. This adaptation enables the video stream to maintain quality during active scenes, providing a clearer and more detailed representation of the movement.

In contrast, options that mention I-frames, automatic adjustment of bitrate settings, or general increases in data transmission do not directly address how movement affects the size of specific frame types and their contribution to the overall bitrate during dynamic scenes.