Optimization of mp3 encoding with complete decoder compatibility
AssigneeResearch In Motion Limited
InventorsGuixing Wu, En-hui Yang
Life of this patent
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Abstract
An iterative rate-distortion optimization algorithm for MPEG I/II Layer-3 (MP3) encoding based on the method of Lagrangian multipliers. Generally, an iterative method is performed such that a global quantization step size is determined while scale factors are fixed, and thereafter the scale factors are determined while the global quantization step size is fixed. This is repeated until a calculated rate-distortion cost is within a predetermined threshold. The methods are demonstrated to be computationally efficient and the resulting bit stream is fully standard compatible.
Claims20
A method for optimizing audio encoding of a source sequence, the encoding being dependent on quantization factors, the quantization factors including a global quantization step size and scale factors, the method comprising:
- defining a cost function of the encoding of the source sequence, the cost function being dependent on the quantization factors;
- initializing fixed values of the scale factors;
- and
- determining values of the quantization factors which minimize the cost function by iteratively performing:
- determining, for the fixed values of the scale factors, a value of the global quantization step size which minimizes the cost function,
- fixing the determined value of the global quantization step size and determining values of scale factors which minimize the cost function, and fixing the determined values of the scale factors, and
- determining whether the cost function is below a predetermined threshold, and if so ending the iteratively performing.
An encoder for optimizing audio encoding of a source sequence, the audio encoding being dependent on quantization factors, the quantization factors including a global quantization step size and scale factors, the encoder comprising:
- a controller;
- a memory accessible by the controller, a cost function of the encoding of the source sequence stored in memory, the cost function being dependent on the quantization factors;
- and
- a predetermined threshold of the cost function stored in the memory,
- wherein the controller is configured to:
- access the cost function and predetermined threshold from memory,
- initialize fixed values of the scale factors, and
- determine values of the quantization factors which minimize the cost function by iteratively performing:
- determining, for the fixed values of the scale factors, a value of the global quantization step size which minimizes the cost function,
- fixing the determined value of the global quantization step size and determining values of scale factors which minimize the cost function, and fixing the determined values of the scale factors, and
- determining whether the cost function is below the predetermined threshold, and if so ending the iteratively performing.
Dependencies are inferred from the claim text.