US 5,334,977 A · ADPCM transcoder wherein different bit numbers are used in code conversion

Abstract

For transmission and reception of an ADPCM stream in which each of signal components is represented by a predetermined number of bits, an ADPCM transcoder comprises a bit number determining device (43) for producing a bit number signal representative of first and second bit numbers one at a time to make the ADPCM stream carry a voice component with the first bit number and a data component with the second bit number as two of the signal components. The first bit number is less than the second bit number. Preferably, a sum of the first and the second bit numbers is not greater than twice the predetermined number to make one of the two signal components comprise the voice component and a less significant part of the data component. The first and the second bit numbers are calculated from a voice and a data optimum scale factor which can be calculated by a method similar to adaptive prediction. The bit number signal need not be carried by the ADPCM stream. Alternatively, the transcoder may multiplex the bit number signal in the ADPCM stream for transmission and demultiplex the bit number signal from the ADPCM stream received to determine the first and the second bit numbers for use in an ADPCM decoder included therein.

Claims9

Dependent claims

An adaptive differential PCM transcoder which is for code converting two PCM streams to one adaptive differential PCM stream and which includes an adaptive differential PCM encoder device for encoding two PCM sequences into one adaptive differential PCM sequence and a format transforming device for format transforming said two PCM streams into said two PCM sequences and said adaptive differential PCM sequence into said adaptive differential PCM stream, said adaptive differential PCM transcoder comprising:

a scale factor calculating device for using said adaptive differential PCM sequence in calculating a voice optimum scale factor and a data optimum scale factor;
a judging device for comparing said data optimum scale factor with a predetermined threshold value to judge presence and absence of a data component in said two PCM sequences;
a bit number determining device for selecting a bit number in accordance with the absence and the presence of said data component to produce a bit number signal representative of said bit number;
a first connection for supplying said bit number signal to said adaptive differential PCM encoding device to make said adaptive differential PCM encoder device use said bit number in encoding said two PCM sequences into said adaptive differential PCM sequence;
and
a second connection for supplying said bit number signal to said format transforming device to make said format transforming device use said bit number in format transforming said adaptive differential PCM sequence into said adaptive differential PCM stream.

3 more elements

Dependencies are inferred from the claim text.

ADPCM transcoder wherein different bit numbers are used in code conversion

Life of this patent

ADPCM transcoder wherein different bit numbers are used in code conversion

Life of this patent

Abstract

Claims9