- I‑frames are the least compressible but don’t require other video frames to decode.
- P‑frames can use data from previous frames to decompress and are more compressible than I‑frames.
- B‑frames can use both previous and forward frames for data reference to get the highest amount of data compression.
An I‑frame (Intra-coded picture), a complete image, like a JPG or BMP image file. P and B frames hold only part of the image information (the part that changes between frames), so they need less space in the output file than an I‑frame.
A P‑frame (Predicted picture) holds only the changes in the image from the previous frame. For example, in a scene where a car moves across a stationary background, only the car’s movements need to be encoded. The encoder does not need to store the unchanging background pixels in the P‑frame, thus saving space. P‑frames are also known as delta‑frames.
A B‑frame (Bidirectional predicted picture) saves even more space by using differences between the current frame and both the preceding and following frames to specify its content.
