I frame: intra-frame encoded frame
I-Frame features:
1. It is a full frame compression encoded frame. It will encode and transmit the full frame image information in JPEG compression.
2. Decoding the full image can be reconstructed with the data of I-frame only;
3.I Frame describes the image background and the details of the moving body;
4.I frames do not need to refer to other images to generate;
The 5.I frame is a reference frame of P-frame and B-frame (its mass directly affects the quality of subsequent frames in the same group);
The 6.I frame is the base frame of the frame group GOP (first frame), with only one I frame in a group;
7.I frames do not need to consider motion vectors;
The amount of data that the 8.I frame occupies is relatively large.
P Frame: forward prediction encoded frame.
P-Frame prediction and reconstruction: P-Frame is based on I-frame as reference frame, in I-frame to find the P-frame "a point" of the predicted value and motion vector, take the predicted difference and the motion vector transmission together. A complete P-frame can be obtained by finding the predicted value of the P-frame "point" from the I-frame at the receiving end and adding it to the difference to get the P-frame "some" sample value.
P-Frame features:
The 1.P frame is an encoded frame that is separated by one or more frames after the I frame;
The 2.P Frame uses the motion compensation method to transmit its difference and motion vectors (prediction error) with the previous I or P frames .
3. Decoding must sum the predicted value in I frame with the prediction error to reconstruct the complete P-frame image;
4.P frames belong to the inter-frame encoding of the forward prediction. It refers only to the I-frame or P-frame closest to it;
A 5.P frame can be a reference frame of the P-frame behind it, or a reference frame of a B-frame before and after it .
6. Since P-frame is a reference frame, it may cause the spread of decoding errors;
7. Due to the difference in transmission, p-frame compression is relatively high.
B-Frame: bidirectional prediction interpolation encoded frames.
prediction and reconstruction of B-frame
The B-frame is the reference frame of the front I or P frame and the following P-frame, "finds" the predicted value of "a point" of B-frame and two motion vectors, and takes the predicted difference and motion vector transmission. The receiving end "finds out" the predicted value according to the motion vector in two reference frames and sums it with the difference, obtains the B-frame "Some point" sample value, thus obtains the complete B-frame.
B-Frame features
1.B frames are predicted by the front I or P frames and the following p-frames;
The 2.B frame transmits the prediction error and the motion vector between it and the front I or p frame and the back p frame;
3.B frames are bidirectional predictive coded frames;
The 4.B frame compression ratio is the highest, because it only reflects the change of the moving body between the reference frames, the prediction is more accurate;
5.B frames are not reference frames and do not cause a spread of decoding errors.
Note: I, B, p frames are based on the needs of the compression algorithm, are human-defined, they are real physical frames, as to which frame in the image is the I-frame, is random, one but to determine the I-frame, the subsequent frames are strictly in accordance with the specified order.
Features of I-frames, p-frames, and B-frames
