Picture layer rate control for video encoding
AssigneeSharp Laboratories of America, Inc.
InventorsZhi Zhou, Shijun Sun
Life of this patent
Estimating the term…
Abstract
A one-pass picture-layer rate control (RC) method and system for controlling a video encoder: The bit allocation and determination of quantization parameter (QP) in this rate control method and system are based on a Rate-Quantization (R-Q) scale model. The R-Q model is a linear one, wherein the number of bits per picture is in reverse ratio of quantization scale for that picture. A conversion of exponential-based QP to linear-scaled QP is taken in the calculation of complexity model and determination of QP. The conversion is integer-based and is consistent with the quantization array defined in the H.264 standard.
Claims20
1) A method for one pass, picture layer, rate control for a video encoder that encodes a video stream that includes a series of pictures, said method including the steps of;
- determining the complexity of the pictures in a forward sliding window that covers a plurality of pictures including a current picture,
- calculating a target number of bits for each current picture using the complexity ratio of said current picture and the sum of the complexity of all pictures remaining in the current sliding window, the complexity of each particular picture being calculated using a linear rate quantization scale model,
- calculating a quantization parameter (QP) for each current picture using said calculated target number of bits and a quantization scale determined by said rate quantization scale model, and
- controlling said encoder using said quantization parameter (QP).
12) A rate control for a video encoder that encodes a video stream of I, P, and B pictures, said stream having a particular Bit_rate and Picture_rate, said method utilizing a forward sliding window that covers a plurality of pictures, said method including the steps of:
- initializing the value of the bits (Br) in the current sliding window by:
- B
- r
- =
- N
- win
- *
- Bit_rate
- Picture_rate
- where Nwin is the number of pictures in the sliding window,
- calculating the target for the number of bits (Target_bits) as
- Target_bits
- =
- X
- cur
- K
- cur
- (
- N
- i
-
- X
- i
- K
- i
- +
- N
- p
-
- X
- p
- K
- p
- +
- N
- b
-
- X
- b
- K
- b
- )
- *
- B
- r
- where, Ni Np and Nb are the remaining numbers of I, P, B picture in the current sliding window respectively, Xi, Xp and Xb are the complexity measurements of I, P, B pictures, Ki, Kp and Kb are constants to control the relative importance for I, P and B pictures,
- clipping the target number of bits per picture by:
- Target_bits
- =
- max
-
- (
- Target_bits
- ,
- Bit_rate
- 16
- *
- Picture_rate
- )
- .
14) A system for one pass, picture layer, rate control for a video encoder that encodes a video stream that includes a series of pictures, said system including;
- means for determining the complexity of the pictures in a forward sliding window that covers a plurality of pictures including a current picture,
- means for calculating a target number of bits for each current picture using the complexity ratio of said current picture and the sum of the complexity of all pictures remaining in the current sliding window, the complexity of each particular picture being calculated using a linear rate quantization scale model,
- means for calculating a quantization parameter (QP) for each current picture using said calculated target number of bits and a quantization scale determined by said rate quantization scale model, and
- means for controlling said encoder using said quantization parameter (QP).
Dependencies are inferred from the claim text.