Method and apparatus for rate control for constant-bit-rate-finite-buffer-size video encoder
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 L 1 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.
1. A method for rate control for a constant-bit-rate finite-buffer-size video encoder comprising:
obtaining, by the video encoder, a scene change indication from a prediction error image;
using, by the video encoder, the scene change indication from the prediction error image to reset a global complexity history associated with frames of video;
using the global complexity history to provide the rate control for the video encoder encoding the video frames;
wherein the obtaining the scene changes indication from the prediction error image further comprises:
counting a first number of intra-code pixel blocks in the prediction error image;
counting a second number of non-intra code pixel blocks in the prediction error image;
calculating a ratio of the first number and the second number;
comparing the ratio to a threshold to determine a result; and
using the result as the scene change indication.
2. The method of claim 1 comprising producing global complexity values for the global complexity history using a scene change adaptive low-pass filter.