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Method for B frame code rate controlling

A technology of frame bit rate and calculation method, applied in the field of video coding, can solve the problems of difficult to satisfy buffer constraints and smooth video quality at the same time, weak real-time control ability of bit rate control, overflow or underflow of buffer capacity, etc.

Inactive Publication Date: 2011-05-11
SICHUAN PANOVASIC TECH
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Problems solved by technology

In the JVT-G012 code rate control method, the QP value of the B frame is based on the average value of the QP of the encoded P frames on both sides of the B frame. When the number of B frames between two P frames is large, the B The frame rate control method is difficult to meet the constraints of the buffer and the smooth video quality requirements, especially when the video changes rapidly, because the real-time control ability of the rate control is weak, the overflow or underflow of the buffer capacity often occurs overflow and large fluctuations in video quality

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  • Method for B frame code rate controlling
  • Method for B frame code rate controlling
  • Method for B frame code rate controlling

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[0051] This part mainly explains the BQP(n, i) situation obtained by two consecutive P frames, different QP values ​​of n-1 and nth P frames, and different M values ​​and different threshold TQP.

[0052] In the process of bit rate control, in order to avoid violent fluctuations in video quality, the QP value change of two consecutive P frames is generally limited to ±2, so the change range of DQP(n) is limited to -2≤DQP(n) ≤2, in this specific example, the values ​​of BQP(n, i) under different values ​​of DQP(n) will be listed. and in the example C 1 =C 2 =0, and assume that the PQP(n) value is fixed at 30.

[0053] 1. QP calculation method to ensure smooth video quality: TQP=2, M=2, ω 1 = ω 2 =1, calculate the QP value of the B frame according to the formula (1)

[0054] Case 1:

[0055] Changes in the QP value at the encoding end:

[0056]

[0057] Changes in the QP value at the decoding end:

[0058]

[0059] Case 2:

[0060] Changes in the QP value at the e...

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Abstract

The present invention discloses a method for controlling B-frame code rate. In the video coding process, when the B frame in the video image group is coded, a quantified parameter threshold TQP is firstly set, and then the quantified parameter difference DQP used for I frame and P frame or two continuous P frame is calculated. Then comparison between quantified parameter threshold TQP and quantified parameter difference DQP is executed. If the absolute value of quantified parameter difference DQP is less than quantified parameter threshold TQP, a QP calculation method which guarantees the smoothness of video quality is adopted for calculating the B-frame quantified parameter BQP. If the absolute value of quantified parameter difference DQP is larger than quantified parameter threshold TQP, a QP calculation method which guarantees the smooth capability of data in the buffer area is adopted for calculating the B-frame quantified parameter BQP. Thus the QP calculating method which guarantees the smooth video quality is adopted when the variation of QP of P frame is smooth. The QP calculating method which guarantees the smoothness of data capability in the buffer area is adopted when variation of QP of P frame is furious. Thus a better compromise is realized between the smoothness of video quality at the decoding end and the smoothness of data capacity of buffer area at the encoding end.

Description

technical field [0001] The invention relates to the technical field of video coding, in particular to a method for controlling the code rate of B frames in a video image group. Background technique [0002] A video source is composed of a sequence of video images, which are divided into different GOPs, ie groups of video images. In the video image group, it can be composed of three different video image frames, namely I frame, P frame and B frame. The I-frame is an intra-frame prediction frame, and its video image is compressed and encoded through the image information in this frame. The encoding efficiency of this mode is often not high. The P frame is an inter-frame prediction frame, which adopts the inter-frame motion compensation technology, that is, predicts the current frame by using the information of the previous coded frame. The B frame is a bidirectional inter-frame prediction frame. It can use the previous encoded frame or the subsequent frame, or use the inform...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04N7/26H04N19/146H04N19/152
Inventor 方春鲁国宁
Owner SICHUAN PANOVASIC TECH