What defines the size of P frames in video encoding?

P frames, or predictive frames, in video encoding are primarily defined by the amount of change between frames. This means that P frames store only the differences from their preceding frame, rather than the entire image as in I frames (intra-coded frames). By doing this, P frames can achieve better compression efficiency because they leverage temporal redundancy, capturing only the pixels that have changed since the last frame, rather than repeating information.

The size of P frames can greatly vary depending on how much movement or change occurs in the scene between frames. If there is minimal change, the P frame can be very small because it only needs to transmit a few differences. Conversely, if there is significant change, the P frame will be larger due to more data needing to be encoded to represent the alterations from the previous frame.

The resolution of the video influences the overall amount of data available but does not directly define the size of P frames. Similarly, while the frame rate may impact how often frames are changed, it does not dictate the specific size of these predictive frames. Color depth pertains to how much color information is captured in each pixel but, again, does not directly correlate to the size of P frames. Thus, the correct choice is centered on the changes between frames,