Method for dual pass rate control video encoding

摘要

A method of dual-pass rate control video encoding and an encoder are disclosed. Uncompressed input video is received with a video encoder. First pass encoding is performed, and a second pass encoding is performed with the video encoder at a delay relative to the first pass. The first pass encoding detects scene changes within the input video, assigns macroblocks to a pre-determined number of activity classes, and determines a complexity of each picture within the sequence of pictures. Information from the first pass encoding concerning the scene changes, the activity classes, and the complexity are used for rate control determined in second pass encoding for producing and outputting a bit stream of compressed video. During at least one of the first pass and second pass encoding, boundaries of at least some of the GOPs are adjusted to be aligned with the scene changes.

主权项

1. A method of dual-pass rate control video encoding, comprising:
receiving uncompressed input video including a sequence of pictures with a video encoder, the input video including a plurality of contiguous sequences of pictures each referenced to as a Group of Pictures (GOP) that, when coded, begin with an I-picture in display order and end with a last picture before a next I-picture; performing a first encoding pass of the uncompressed video with the video encoder; and performing a second encoding pass for rate control of the uncompressed video with the video encoder at a delay relative to the first encoding pass; during the first encoding pass:
detecting scene changes within the input video,assigning macroblocks to a pre-determined number of activity classes,determining a complexity of each picture within the sequence of pictures, andgenerating an average macroblock activity per activity class for use during the second encoding pass,the macroblocks each being a rectangular array of luma samples and two corresponding blocks of chroma samples in the pictures, the activity classes each being a defined class of macroblocks based on luma values of the pictures of the input video, and the complexity being a number of bits generated per picture and activity class; during the second encoding pass:
using information from the first encoding pass concerning the scene changes, the activity classes, the complexity, and the average macroblock activity per activity class to produce the rate control, andproducing a bit stream of compressed video; and during at least one of the first encoding pass and the second encoding pass, one or more boundaries of at least some of the GOPs are adjusted to be aligned with the scene changes.