Method and apparatus for partially recompressing digital signals

Claim 2

A method in accordance with claim 1 wherein: said digital information comprises video information; said first compression scheme uses motion estimation to precompress said video information prior to said transformation and quantization steps; and said step of partially decompressing the already compressed digital video information preserves the precompressed information without attempting to decompress it.

Claim 3

A method in accordance with claim 1 or 2 wherein: said first compression scheme variable length encodes the quantized transform coefficients at said first resolution; said step of partially decompressing the already compressed digital information variable length decodes the encoded quantized coefficients and inverse quantizes the results to recover the transform coefficients as they were prior to quantizing; and said step of using the requantized transform coefficients to provide said digital information at a different compression level variable length encodes the requantized transform coefficients.

Claim 6

A method in accordance with claim 5 wherein said coefficient resolution is dynamically adjustable in response to real time requirements of said intended application.

Claim 7

A method in accordance with claim 5 or 6 wherein said intended application comprises the synchronization of a plurality of fixed rate compressed digital information streams by further compressing at least one of said streams to reduce its effective data rate.

Claim 8

A method in accordance with claim 5 or 6 wherein said intended application comprises the adjustment of the data rates of digital information data streams provided in a statistically multiplexed form to maintain said streams within an available bandwidth.

Claim 9

A method in accordance with claim 5 or 6 wherein said intended application comprises the adjustment of the amount of data provided in a digital information stream to enable the storage of said information within an available storage space.

Claim 11

A method in accordance with claim 10 wherein: said digital information comprises video information; said requantizing step requantizes the recovered transform coefficients to a lower resolution than provided by said first compression scheme; and said selected portions are limited to information that is not used to predict past or future video frames.

Claim 12

Apparatus for compressing a received digital signal to a new compression level, the received signal having already been compressed by a first compression scheme that provided transform coefficients and then quantized said transform coefficients to provide quantized coefficients at a first resolution, said apparatus comprising: an inverse quantizer for recovering said transform coefficients from quantized coefficients provided by said received digital signal; and a quantizer coupled to receive the recovered transform coefficients without further decompression thereof for requantization at a second resolution that is different from said first resolution.

Claim 13

Apparatus in accordance with claim 12 wherein said quantized coefficients are variable length encoded by said first compression scheme, said apparatus comprising: means for variable length decoding the quantized coefficients prior to said inverse quantizer; and means for variable length encoding the requantized transform coefficients from said quantizer.

Claim 14

Apparatus in accordance with claim 12 or 13 further comprising: means for selecting portions of the received signal for processing by said inverse quantizer and said quantizer to provide those portions at said new compression level, with other portions of the received signal remaining at the compression level provided by said first compression scheme.

Claim 15

Apparatus in accordance with claim 14 wherein: said digital information comprises video information; and said selected portions are limited to information that is not used to predict past or future video frames.

Claim 16

Cable television distribution apparatus comprising: a satellite downlink for receiving a first digital signal that has been compressed by a first compression scheme that provided transform coefficients and then quantized said transform coefficients to provide quantized coefficients at a first resolution; an inverse quantizer for recovering said transform coefficients from quantized coefficients provided by said received digital signal; a quantizer coupled to receive the recovered transform coefficients without further decompression thereof for requantization at a second resolution that is different from said first resolution; and means for distributing a second digital signal formed from said requantized transform coefficients to a plurality of subscribers instead of distributing said first digital signal to said subscribers.

Claim 17

Apparatus in accordance with claim 16 wherein said second resolution is lower than said first resolution to render the bandwidth of said second digital signal smaller than the bandwidth of said first digital signal.

Claim 18

Apparatus in accordance with claim 16 or 17 wherein said quantized coefficients are variable length encoded by said first compression scheme, said apparatus comprising: means for variable length decoding the quantized coefficients prior to said inverse quantizer; and means for variable length encoding the requantized transform coefficients from said quantizer.

Claim 19

Apparatus in accordance with one of claims 16 to 18 further comprising: means for selecting portions of the received first digital signal for processing by said inverse quantizer and said quantizer to provide those portions at said new compression level, with other portions of the received signal remaining at the compression level provided by said first compression scheme.

Claim 20

Apparatus in accordance with claim 19 wherein: said digital information comprises video information; and said selected portions are limited to information that is not used to predict past or future video frames.