Bell Communications Research, Inc.

Orni Petruschka

Milton M Anderson

Apparatus and methods are disclosed for recovering alignment from a non-ideally encoded multi-bit digital signal without the need to embed framing information within the encoded signal or append framing bits thereto. In particular, the invention is disclosed in the context of recovering septet alignment in a sub-band ADPCM (adaptive differential pulse code modulated) 7 kHz audio digital signal without the need to embed any framing information within the digital signal itself. Specifically, in this context, this method relies on first gathering statistics from a 56 kbit/second 7 kHz audio digital signal itself for a pre-defined number of incoming bits that occur during a measurement interval and for every one of seven possible alignments for a septet. Once these statistics are gathered, the alignment is selected to be that which satisfies various pre-defined statistical tests that are dictated by non-uniform deterministic characteristics that occur in the ADPCM audio digital signal itself, once it is properly aligned, and specifically certain characteristics which exist in a distribution of the occurrences of the different combinations of the four most significant bits of the low-band ADPCM codewords situated within properly aligned ADPCM septets that occurred during the measurement interval.

Apparatus and methods for recovering alignment from a non-ideally

Apparatus and method for analyzing a bit stream to determine whether the stream is encoded in A-law PCM or .mu.-law PCM. Bit positions 2, 3, and 4 are examined to determine which of the 8 possible segment codes are present. Segment codes representing low amplitude speech should predominate statistically over segment codes representing high amplitude speech. If the sample cannot be classified by the appearance of low amplitude segments, the higher amplitude segments are compared and that coding law is detected as being present which accrues the lower count for such high amplitude segments.

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Middletown, NJ, United States of America

Orni Petruschka