I, P, B frame and PTS, < DTS; >

The basic concept:

I frame : The intra coded frames also known as intra picture, I frame is usually each GOP (a video using the MPEG compression technology) of the first frame, after moderate compression, as a random access point of reference, can be used as the image. Frames can be seen as a product of the compressed image through.

P frame: forward predictive coded frame is also called predictive-frame, coding image compression and transmission of data through the full will be less than the time redundancy information in the image sequence of encoded frames to front, also called predictive frame,

B frame: bi-directional prediction interpolation coding frame is also called bi-directional interpolated prediction frame, both the source and the front image sequences encoded frame, encoded image also takes into consideration the temporal redundancy information between behind the source image sequence of encoded frames to compress the data quantity, also called Bi predictive frames,

PTS: Presentation Time Stamp. PTS is mainly used to measure what time video frames decoded are displayed

DTS: Decode Time Stamp. DTS is mainly a sign reading memory in the bit began to flow into the decoder decodes what time.

In the absence of sequence and PTS DTS B frame in the presence of the order should be the same.

IPB frame difference:

I frame: itself can be a separate picture through video decompression algorithm decompression.

P frame: Need to refer to the front of a I frame or B frame to generate a complete picture.

A P frame B frame: will refer to the previous I or P frame and the back to create a complete picture.

A GOP is formed between the two I frame, through the parameters to set the size of the BF, which can at the same time in the x264: the number of between I and P or two P B.

Through the above illustrates the basic if the last frame B the presence of frame a GOP must be P.

DTS and PTS in different:

DTS is mainly used for video decoding,.PTS used in the decoding stage is mainly used for synchronization and output video. Used in display. The output sequence.DTS in the absence of B the case of frame and PTS are the same

Example:

Below is a GOP 15 examples, the decoded reference frame and decoding order are in there:

Pictured: I frame decoding is not dependent on any other frames. Decoding and P frame decoding depends on the front of the I frame or P frame.B frame is dependent on the front of a recent I frame or P frame and following a recent P frame

Posted by Adolph at March 25, 2014 - 10:50 AM