Multi-pass video encoding method

Abstract

Some embodiments of the invention provide a multi-pass encoding method that encodes several images (e.g., several frames of a video sequence). The method iteratively performs an encoding operation that encodes these images. The encoding operation is based on a nominal quantization parameter, which the method uses to compute quantization parameters for the images. During several different iterations of the encoding operation, the method uses several different nominal quantization parameters. The method stops its iterations when it reaches a terminating criterion (e.g., it identifies an acceptable encoding of the images).

Description

Background technique [0001] A video encoder encodes a sequence of video images (eg, video frames) by utilizing various encoding schemes. Video coding schemes typically encode video frames or portions of video frames (eg, sets of pixels within a video frame) in an intraframe or interframe manner. Intra-coded frames or sets of pixels are encoded independently of other frames or sets of pixels within other frames. An inter-coded frame or set of pixels is encoded by reference to one or more other frames or sets of pixels within other frames. [0002] When compressing video frames, some encoders implement a "rate controller" that provides a "bit budget" for the video frame or set of video frames to be encoded. The bit budget specifies the number of bits that have been allocated to encode the video frame or set of video frames. By efficiently allocating the bit budget, the rate controller attempts to generate the highest quality compressed video stream taking into account certain...

AI Technical Summary

Problems solved by technology

To date, not many rate controllers take into account the spatial or temporal complexity of a frame or set of pixels within a frame in controlling their bitrate

Also, most multi-pass rate controllers do not adequately search the solution space for encoding solutions that use optimal quantization parameters for frames and / or intra-frame pixel sets taking into account the desired bit rate

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