Audio Spectrum Encoding With Adaptive Huffman Band Indices
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Audio signal encoding using Huffman coding is not optimal when signal statistics vary significantly from the predefined Huffman table, often resulting in higher bit consumption compared to fixed-length coding, especially due to the phenomenon of auditory masking.
Innovation Solution
The solution involves exploring auditory masking properties to narrow the range of differential indices, allowing for the design of Huffman tables with fewer code words, which reduces bit consumption by using shorter code lengths for encoding differential indices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Huffman coding is used for encoding audio signal quantization indices, then bit consumption is reduced for signals matching the Huffman table statistics, but bit consumption increases for signals with statistics significantly different from the Huffman table
Solution Approach 1:
The patent implements dynamic Huffman coding by allowing the encoder to switch between a predefined Huffman table and a dynamically generated Huffman table based on the actual statistics of the input signal. The encoder calculates the statistics of quantization indices, compares them with the predefined table, and adaptively selects or generates the most suitable Huffman table to minimize bit consumption for the current signal characteristics.
Solution Approach 2:
The patent changes the parameters of the Huffman coding system by allowing the code table itself to be modified based on signal statistics. When the predefined Huffman table is not suitable, the encoder generates a new Huffman table with code lengths optimized for the actual signal distribution, thereby adapting the coding parameters to match the input signal characteristics and reduce bit consumption.
2Productivity
If a predefined Huffman table is used for encoding, then encoding speed is improved, but encoding efficiency deteriorates when signal statistics differ from the predefined table
Solution Approach 1:
The patent introduces dynamic adaptation to the Huffman coding process by enabling the encoder to switch between a fast predefined Huffman table and a customized dynamically generated Huffman table. When the predefined table provides good compression, it is used for fast encoding; when signal statistics deviate significantly, a dynamic Huffman table is generated to optimize compression efficiency, balancing speed and efficiency based on actual signal characteristics.
Solution Approach 2:
The patent performs preliminary analysis of the signal statistics before encoding to determine whether the predefined Huffman table is suitable. By pre-calculating and comparing signal statistics with the predefined table characteristics, the encoder can proactively select the appropriate coding strategy, avoiding suboptimal encoding and reducing overall bit consumption while maintaining efficient encoding performance.
Data Source
AI summary
An audio/speech encoding method is provided that includes transforming a time domain input signal to a frequency spectrum, and dividing the frequency spectrum to a plural of bands. The method also includes calculating a level of energies for each band, quantizing the energies for the each band, and calculating differential indices. The method additionally includes modifying a range of the differential indices for the Nth band when N is an integer of 2 or more, and replacing the differential index with the modified differential index, and not modifying a range of the differential indices for the Nth band when N is an integer of 1. The method further includes encoding the differential indices using a Huffman table selected based on a minimum value and a maximum value of the differential indices, and transmitting the encoded differential indices and a flag signal for indicating the selected Huffman table.