Multi-pass variable bitrate media encoding
First Claim
1. In a computer system, a computer-implemented method of media encoding according to a multi-pass variable bitrate control strategy, the method comprising:
- in a first pass, encoding multi-channel media data partitioned into plural variable-size chunks for the encoding, wherein the plural variable-size chunks are plural tiles of the media data;
processing results of the encoding in the first pass to determine one or more control parameters for the media data; and
in a second pass, encoding the media data according to the one or more control parameters in view of a goal of uniform quality at variable bitrate.
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Abstract
An encoder uses multi-pass VBR control strategies to provide constant or relatively constant quality for VBR output while guaranteeing (within tolerance) either compressed file size or, equivalently, overall average bitrate. The control strategies include various techniques and tools, which can be used in combination or independently. For example, in a first pass, an audio encoder encodes a sequence of audio data partitioned into variable-size chunks. In a second pass, the encoder encodes the sequence according to control parameters to produce output of relatively constant quality. The encoder sets checkpoints in the second pass to adjust the control parameters and/or subsequent checkpoints. The encoder selectively considers a peak bitrate constraint to limit peak bitrate. The encoder stores auxiliary information from the first pass for use in the second pass, which increases the speed of the second pass. Finally, the encoder compares signatures for the input data to check consistency between passes.
169 Citations
20 Claims
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1. In a computer system, a computer-implemented method of media encoding according to a multi-pass variable bitrate control strategy, the method comprising:
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in a first pass, encoding multi-channel media data partitioned into plural variable-size chunks for the encoding, wherein the plural variable-size chunks are plural tiles of the media data; processing results of the encoding in the first pass to determine one or more control parameters for the media data; and in a second pass, encoding the media data according to the one or more control parameters in view of a goal of uniform quality at variable bitrate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. In a computer system, a computer-implemented method of audio encoding according to a multi-pass variable bitrate control strategy, the method comprising:
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in a first pass, encoding audio data, including computing triplets for plural chunks of the audio data, wherein each of the triplets includes a value for each of quantization step size, bits, and quality setting; and in a second pass, encoding audio data to produce variable bitrate output at a target quality level. - View Dependent Claims (15, 16)
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17. In an audio encoder, a computer-implemented method of audio encoding according to a multi-pass variable bitrate control strategy, the method comprising:
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in a first pass, encoding a sequence of multi-channel audio data, wherein the sequence includes plural chunks, and wherein the plural chunks are tiles of the audio data; and in a second pass, encoding the sequence of audio data in view of a goal of uniform quality at variable bitrate, wherein the encoding in the second pass includes checking results at each of plural checkpoints, and wherein each of the plural checkpoints is separated from other checkpoints by at least two chunks. - View Dependent Claims (18, 19, 20)
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Specification