Digital conversion from one pcm format to another

Claim 2

Apparatus for converting an applied signal encoded in ADPCM format to a signal encoded in ADPCM format, which comprises, means responsive to that sequence of signals within said applied ADPCM signal indicative of the quantization level utilized in encoding said applied signal for developing a digital scale factor, means for digitally scaling each word of said signal in said first ADPCM format by said digital scale factor, means for accumulating said digitally scaled words, and means for truncating each of said digitally scaled words to the number of significant bits prescribed for representing said applied signal in said second ADPCM format.

Claim 3

A digital ADPCM to DPCM signal format conversion system, which comprises, scaling means responsive to that sequence of signals Within an applied AMDPCM digital signal which indicates the encoding quantizer level of said applied signal, said scaling means developing a scale factor representative of the extent of companding employed in predictively coding said signal, means for digitally scaling each word of said applied signal by said factor, and means for selecting a prescribed portion of each scaled word to form words in a DPCM code format to represent said applied signal.

Claim 4

A digital ADPCM to DPCM signal format conversion system, which comprises, scaling means responsive to that sequence of signals Within an applied AMDPCM digital signal which indicates the encoding quantizer level of said applied signal, said scaling means developing a scale factor representative of the extent of companding employed in predictively coding said signal, means for digitally scaling each word of said applied signal by said factor, and means for selecting a prescribed portion of each scaled word to form words in a DPCM code format to represent said applied signal.

Claim 5

A digital ADPCM to DPCM signal format conversion system, which comprises, means for logically examining a message signal digitally coded in ADPCM format to determine constraints applied thereto during coding for the removal of redundancy from said message signal, means responsive to said determined encoding constraints for digitally multiplying said digital words by a scale factor selected to develop product digital words in which redundancy in said message signal is redistributed, and means for truncating said product words to the number of bits selected for DPCM code format to represent said message signal.

Claim 6

A digital ADPCM to DPCM signal format conversion system, which comprises, means for logically examining a message signal digitally coded in ADPCM format to determine constraints applied thereto during coding for the removal of redundancy from said message signal, means responsive to said determined encoding constraints for digitally multiplying said digital words by a scale factor selected to develop product digital words in which redundancy in said message signal is redistributed, and means for truncating said product words to the number of bits selected for DPCM code format to represent said message signal.

Claim 7

A digital signal format conversion system, as defined in claim 3, wherein said means for logically examining digital words in said ADPCM code format includes, means for sensing a predetermined number of consecutive identical digital words, and means for assigning a multiplier scale factor in accordance with the digital value of said sensed words.

Claim 8

A digital signal format conversion system, as defined in claim 4, wherein said scale factor is selected to be identical to the scale factor employed in representing said message signal in said first code format.

Claim 9

A digital system for converting a digital ADPCM representation of a message signal to a digital DPCM representation thereof, which comprises, logic means responsive to that sequence of signals within an applied ADPCM signal indicating the encoding quantizer level of said applied ADPCM signal, said logic means developing a digital scale factor representative of the effective quantizer characteristic employed in predictively coding said signal, means for digitally multiplying each word of said ADPCM signal by said scale factor to produce a digital product, means for selecting a prescribed number of most significant bits of each digital product word, means for recovering least significant bits of successive product words until a significant bit is accumulated, means for adding accumulated bits to said selected digital product words to produce a corrected product word, and means for utilizing said corrected digital product as a DPCM representation of said applied signal.

Claim 10

A digital system for converting a digital ADPCM representation of a message signal to a digital DPCM representation thereof, which comprises, logic means responsive to that sequence of signals within an applied ADPCM signal indicating the encoding quantizer level of said applied ADPCM signal, said logic means developing a digital scale factor representative of the effective quantizer characteristic employed in predictively coding said signal, means for digitally multiplying each word of said ADPCM signal by said scale factor to produce a digital product, means for selecting a prescribed number of most significant bits of each digital product word, means for recovering least significant bits of successive product words until a significant bit is accumulated, means for adding accumulated bits to said selected digital product words to produce a corrected product word, and means for utilizing said corrected digital product as a DPCM representation of said applied signal.

Claim 11

A system for converting digital ADPCM representation of a message signal to a digital DPCM representation thereof, as defined in claim 6, wherein, said DPCM representation of said applied signal is additionally accumulated on a word-by-word basis to produce a PCM representation of said applied signal.