Method and apparatus for rate control for constant-bit-rate finite-buffer-size video encoder

• US 7,277,483 B1
• Filed: 04/18/2000
• Issued: 10/02/2007
• Est. Priority Date: 04/18/2000
• Status: Expired due to Term

• Current Assignee: ATI Technologies ULC (Advanced Micro Devices, Inc.)
• Original Assignee: ATI International SRL (Advanced Micro Devices, Inc.)
• Inventors: Eckart, Stefan
• Primary Examiner(s): Philippe; Gims
• Assistant Examiner(s): REKSTAD, ERICK J
• Application Number:
  US09/552,761
• Time in Patent Office: 2,723 Days
• Field of Search: 358/133, 358/141, 348/404, 348/405, 348/419, 348/420, 348/700, 348/384, 348/412, 348/413, 348/415, 348/390, 382/232, 382/238, 375/240.02, 375/240.03, 375/240.04, 375/240.13, 375/240.15
• US Class Current: 375/240.03
• CPC Class Codes: H04N 19/115 Selection of the code volume for a coding unit prior to coding
• CPC Class Codes: H04N 19/12 Selection from among a plurality of transforms or standards, e.g. selection between discrete cosine transform [DCT] and sub-band transform or selection between H.263 and H.264
• CPC Class Codes: H04N 19/124 Quantisation
• CPC Class Codes: H04N 19/14 Coding unit complexity, e.g. amount of activity or edge presence estimation H04N19/146 takes precedence
• CPC Class Codes: H04N 19/142 Detection of scene cut or scene change
• CPC Class Codes: H04N 19/149 by estimating the code amount by means of a model, e.g. mathematical model or statistical model
• CPC Class Codes: H04N 19/152 by measuring the fullness of the transmission buffer
• CPC Class Codes: H04N 19/172 the region being a picture, frame or field
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/177 the unit being a group of pictures [GOP]
• CPC Class Codes: H04N 19/182 the unit being a pixel
• CPC Class Codes: H04N 19/33 in the spatial domain
• CPC Class Codes: H04N 19/423 characterised by memory arrangements H04N19/433 takes precedence
• CPC Class Codes: H04N 19/593 involving spatial prediction techniques
• CPC Class Codes: H04N 19/65 using error resilience

Abstract

A method and apparatus for rate control for a constant-bit-rate finite-buffer-size video encoder is described. Rate control is provided by adjusting the size of non-intra frames based on the size of intra frames. A sliding window approach is implemented to avoid excessive adjustment of non-intra frames located near the end of a group of pictures. A measurement of “power” based on a sum of absolute values of pixel values is used. The “power” measurement is used to adjust a global complexity value, which is used to adjust the sizes of frames. The global complexity value responds to scene changes. An embodiment of the invention calculates and uses L1 distances and pixel block complexities to provide rate control. An embodiment of the invention implements a number of bit predictor block. Predictions may be performed at a group-of-pictures level, at a picture level, and at a pixel block level. An embodiment of the invention resets a global complexity parameter when a scene change occurs.

Claims

1. A method for rate control for a constant-bit-rate finite-buffer-size video encoder comprising:

calculating a reference global complexity for each I frame encoded;

calculating a reference power value for each I frame encoded;

calculating a power value for subsequent frames;

calculating a global complexity by multiplying the reference global complexity by the power value and dividing by the reference power value; and

using the global complexity to adjust a frame size.

2. Apparatus for rate control for a constant-bit-rate finite-buffer-size video encoder comprising:

a prediction error image block to determine L1 distances according to sums of absolute differences;

a complexity estimator block coupled to the prediction error image block to determine non-intra pixel block complexity values and intra pixel block complexity values; and

a number-of-bit predictor operatively coupled to the prediction error image block to receive the L1 distances and to the complexity estimator block to receive the non-intra pixel block complexity values and the intra pixel block complexity values, the number-of-bit predictor to predict a number of bits generated by the video encoder.

3. A method for rate control for a constant-bit-rate finite-buffer-size video encoder comprising:

obtaining a prediction error frame including a plurality of pixel-level error values;

calculating a sum of absolute values of the pixel-level error values for a pixel block of the frame;

calculating an expected number of bits for each pixel block in the frame by multiplying a pixel block complexity value for the pixel block by the sum of the absolute values of the pixel-level error values for the pixel block and dividing by a target quantizer step size for the frame;

using the calculated expected number of bits for each pixel block located in the frame to calculate an expected number of bits for the frame; and

using the expected number of bits for the frame to obtain constant-bit-rate video encoding.

4. The method of claim 3 wherein the calculating the expected number of bits for the frame further comprises:

summing the expected number of bits for each pixel block in the frame.

5. Apparatus for rate control for a constant-bit-rate finite-buffer-size video encoder comprising:

a prediction error image block to determine L1 distances according to sums of absolute differences;

a picture-level rate control block operatively coupled to the prediction error image block to receive the L1 distances and to produce a target quantizer step size for a pixel; and

a complexity estimator block operatively coupled to the prediction error image block to determine non-intra pixel block complexity values and intra pixel block complexity values,

wherein the prediction error image block determines a scene change and provides a scene change indication to the complexity estimator block, the complexity estimator block resetting a global complexity value upon receipt of the scene change indication.