Data processing: speech signal processing – linguistics – language – Speech signal processing – For storage or transmission
Reexamination Certificate
2003-01-08
2004-12-07
Dorvil, Richemond (Department: 2654)
Data processing: speech signal processing, linguistics, language
Speech signal processing
For storage or transmission
C704S219000
Reexamination Certificate
active
06829579
ABSTRACT:
STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
REFERENCE TO A “SEQUENCE LISTING,” A TABLE, OR A COMPUTER PROGRAM LISTING APPENDIX SUBMITTED ON A COMPACT DISK
Not Applicable
BACKGROUND OF THE INVENTION
The present invention generally relates to techniques for processing information. More particularly, the invention provides a method and apparatus for converting CELP frames from one CELP based standard to another CELP based standard, and/or within a single standard but a different mode. Further details of the present invention are provided throughout the present specification and more particularly below.
Coding is the process of converting a raw signal (voice, image, video, etc) into a format amenable for transmission or storage. The coding usually results in a large amount of compression, but generally involves significant signal processing to achieve. The outcome of the coding is a bitstream (sequence of frames) of encoded parameters according to a given compression format. The compression is achieved by removing statistically and perceptually redundant information using various techniques for modeling the signal. Hence the encoded format is referred to as a “compression format” or “parameter space”. The decoder takes the compressed bitstream and regenerates the original signal. In the case of speech coding, compression typically leads to information loss.
The process of converting between different compression formats and/or reducing the bit rate of a previously encoded signal is known as transcoding. This may be done to conserve bandwidth, or connect incompatible clients and/or server devices. Transcoding differs from the direct compression process in that a transcoder only has access to the compressed signal and does not have access to the original signal.
Transcoding can be done using brute force techniques such as “tandem” which has a decompression process followed by a re-compression process. Since large amount of processing is often required and delays may be incurred to decompress and then re-compress a signal, one can consider transcoding in the compression space or parameter space. Such transcoding aims at mapping between compression formats while remaining in the parameter space wherever possible. This is where the sophisticated algorithms of “smart” transcoding come into play. Although there has been advances in transcoding, it is desirable to further improve transcoding techniques. Further details of limitations of conventional techniques will be described more fully throughout the present specification and more particularly below.
BRIEF SUMMARY OF THE INVENTION
According to a the present invention, techniques for processing information are provided. More particularly, the invention provides a method and apparatus for converting CELP frames from one CELP based standard to another CELP based standard, and/or within a single standard but a different mode. Further details of the present invention are provided throughout the present specification and more particularly below.
In a specific embodiment, the invention provides an apparatus for converting CELP frames from one CELP-based standard to another CELP based standard, and/or within a single standard but to a different mode. The apparatus has a bitstream unpacking module for extracting one or more CELP parameters from a source codec. The apparatus also has an interpolator module coupled to the bitstream unpacking module. The interpolator module is adapted to interpolate between different frame sizes, subframe sizes, and/or sampling rates of the source codec and a destination codec. A mapping module is coupled to the interpolator module. The mapping module is adapted to map the one or more CELP parameters from the source codec to one or more CELP parameters of the destination codec. The apparatus has a destination bitstream packing module coupled to the mapping module. The destination bitstream packing module is adapted to construct at least one destination output CELP frame based upon at least the one or more CELP parameters from the destination codec. A controller is coupled to at least the destination bitstream packing module, the mapping module, the interpolator module, and the bitstream unpacking module. Preferably, the controller is adapted to oversee operation of one or more of the modules and being adapted to receive instructions from one or more external applications. The controller is adapted to provide a status information to one or more of the external applications.
In an alternative specific embodiment, the invention provides a method for transcoding a CELP based compressed voice bitstream from source codec to destination codec. The method includes processing a source codec input CELP bitstream to unpack at least one or more CELP parameters from the input CELP bitstream and interpolating one or more of the plurality of unpacked CELP parameters from a source codec format to a destination codec format if a difference of one or more of a plurality of destination codec parameters including a frame size, a subframe size, and/or sampling rate of the destination codec format and one or more of a plurality of source codec parameters including a frame size, a subframe size, or sampling rate of the source codec format exist. The method includes encoding the one or more CELP parameters for the destination codec and processing a destination CELP bitstream by at least packing the one or more CELP parameters for the destination codec.
In an alternative specific embodiment, the invention provides a method for processing CELP based compressed voice bitstreams from source codec to destination codec formats. The method includes transferring a control signal from a plurality of control signals from an application process and selecting one CELP mapping strategy from a plurality of different CELP mapping strategies based upon at least the control signal from the application. The method also includes performing a mapping process using the selected CELP mapping strategies to map one or more CELP parameters from a source codec format to one or more CELP parameters of a destination codec format.
Still further, the invention provides a system for processing CELP based compressed voice bitstreams from source codec to destination codec formats. The system includes one or more memories. Such memories may include one or more codes for receiving a control signal from a plurality of control signals from an application process. One or more codes for selecting one CELP mapping strategy from a plurality of different CELP mapping strategies based upon at least the control signal from the application are also included. The one or more memories also include one or more codes for performing a mapping process using the selected CELP mapping strategies to map one or more CELP parameters from a source codec format to one or more CELP parameters of a destination codec format. Depending upon the embodiment, there may also be other computer codes for carrying out the functionality described herein, as well as outside of this specification, which may be combined with the present invention.
Numerous benefits are achieved using the present invention. Depending upon the embodiment, one or more of these benefits may be achieved.
To reduce the computational complexity of the transcoding process.
To reduce the delay through the transcoding process.
To reduce the amount of memory required by the transcoding.
To introduce dynamic rate control
To support silence frames through an embedded voice activity detector.
To provide a framework where various parameter mapping strategies can be used.
To provide a generic transcoding architecture to adapt the current and future diversity CELP based codecs.
The transcoding invention may achieve one or more of these benefits. In a specific embodiment, the transcoding apparatus includes:
a source CELP parameter unpacking module that extracts CELP parameters from the input encoded CELP bitstream;
a CELP parameter interpolator that converts the input source CELP
Gould Stephen
Jabri Marwan A.
Wang Jianwei
Dilithium Networks, Inc.
Dorvil Richemond
Storm Donald L.
Townsend and Townsend / and Crew LLP
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