Rate control strategies for speech and music coding
First Claim
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1. A method for controlling the coding rate of a multimode coding system for coding a current audio signal frame in a sequence of audio signal frames, the method comprising the steps of:
- determining a signal type corresponding to the audio signal of each frame in the sequence of frames;
determining an expected coding rate for the current frame according to the signal type of the audio signal of the current frame and an established average coding rate for the sequence of frames;
estimating a target coding rate for the current frame by adjusting the expected coding rate wherein the adjustment to the expected coding rate is based on the signal type of at least one other frame in the sequence of frames and the status of a bit-stream buffer maintained for buffering coded frames; and
determining a coding rate for use in coding the current frame according to the target coding rate.
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Abstract
A method and a system are provided for controlling the coding rates of a multimode coding system with respect to a sequence of input audio signal frames. The method eliminates or minimizes the overflow and underflow of a bit-stream buffer maintained by the coding system for temporarily recording bit-stream data prior to transmission or storage.
44 Citations
25 Claims
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1. A method for controlling the coding rate of a multimode coding system for coding a current audio signal frame in a sequence of audio signal frames, the method comprising the steps of:
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determining a signal type corresponding to the audio signal of each frame in the sequence of frames;
determining an expected coding rate for the current frame according to the signal type of the audio signal of the current frame and an established average coding rate for the sequence of frames;
estimating a target coding rate for the current frame by adjusting the expected coding rate wherein the adjustment to the expected coding rate is based on the signal type of at least one other frame in the sequence of frames and the status of a bit-stream buffer maintained for buffering coded frames; and
determining a coding rate for use in coding the current frame according to the target coding rate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A coding system for coding a sequence of audio frames corresponding to a digitized sampled input audio signal to generate a series of coded bits, the system comprising:
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a look-ahead buffer for queuing the sequence of frames;
a multimode encoder for receiving frames corresponding to the frames in the look-ahead buffer and encoding the frames into coded bits;
a bit-stream buffer for storing the coded bits generated from the encoder and emitting coded bits; and
a rate controller in connection with the look-ahead buffer and the multimode encoder for controlling the coding mode and coding rate of the multimode encoder, while encoding each frame, according to a characteristic of a current frame, characteristics of all other frames in the sequence, and the status of the bit-stream buffer. - View Dependent Claims (14, 15, 16)
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17. A method for controlling the coding rate for each frame in a sequence of speech data frames in a multimode encoder, the method comprising:
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classifying each frame in the sequence of frames into one of a plurality of predefined classes according to a feature of the frame data, wherein each class is associated with an expected coding rate based on a required average coding rate and the relative importance of data of the class to the perceived quality of a reproduced speech signal;
deriving an adjustment for adjusting the expected coding rate for each frame according to the properties of all frames in the sequence of frames and the status of a bit-stream buffer provided for storing encoded bits corresponding to the frames;
adjusting the expected coding rate based on the derived adjustment; and
determining a coding rate for encoding each frame according to the adjusted expected coding rate. - View Dependent Claims (18, 19)
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20. A method for controlling the coding rate of a multimode coding system for coding a current audio signal frame in a sequence of audio signal frames, the method comprising the steps of:
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determining a signal type corresponding to the audio signal of each frame in the sequence of frames;
estimating a target coding rate for the current frame based on the signal type of at least one other frame in the sequence of frames, the status of a bit-stream buffer maintained for buffering coded frames, and an established average coding rate for the sequence of frames; and
determining a coding rate for use in coding the current frame according to the target coding rate. - View Dependent Claims (21, 22, 23, 24, 25)
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Specification