Encoding and decoding of mac video signals

Claim 2

A MAC signal encoder for encoding a video signal into MAC format, said video signal including a luminance signal and color difference signals and having a marker signal indicating previous MAC encoding of the information therein selectively associated therewith, said encoder comprising: vertical filter means for vertically filtering said color difference signals so as to limit their spectra to a band below a predetermined vertical frequency; vertical sub-sampling means for vertically sub-sampling the color difference signals filtered by said vertical filter means to produce vertically sub-sampled color difference signals, said vertical sub-sampling means being operative to sub-sample said color difference signals at a predetermined sub-sampling rate such that the Nyquist frequency of said vertically sub-sampled color difference signals is substantially the same as said predetermined vertical frequency; multiplexer means for multiplexing the vertically sub-sampled color difference signals with said luminance signal to produce a signal in MAC format; and detector means responsive to said marker signal for selectively inhibiting the operation of said vertical filter means to prevent vertical filtering of said color difference signals thereby.

Claim 3

An encoder according to claim 1, wherein said detector means is responsive to said marker signal contained in the luminance signal.

Claim 4

An encoder according to claim 2, wherein said detector means is responsive to said marker signal contained in a vertical blanking interval of said luminance signal.

Claim 5

An encoder according to claim 3, wherein said detector means is responsive to said marker signal contained in the twenty-first line of a 625 line video signal.

Claim 6

An encoder according to claim 3, wherein said detector means is responsive to said marker signal provided as a peak white level of said luminance signal at a predetermined timing after the start of a line of said vertical blanking interval.

Claim 9

A method according to claim 6, wherein said examining step comprises determining whether said video signal contains said marker signal in said luminance signal.

Claim 10

A method according to claim 7, wherein said examining step comprises determining whether said luminance signal contains said marker signal in a vertical blanking interval thereof.

Claim 11

A method according to claim 8, wherein said examining step comprises examining the twenty-first line of a 625 line video signal to determine whether said marker signal is present therein.

Claim 12

A method according to claim 8, wherein said examining step comprises determining whether said luminance signal includes said marker signal in the form of a peak white level at a predetermined timing after the start of a line of said vertical blanking interval.

Claim 13

A MAC signal decoder for decoding a video signal which is in MAC format containing vertically sub-sampled color difference signals into a video signal in non-MAC format, said decoder comprising: interpolating means for interpolating between said vertically sub-sampled color difference signals to produce estimated color difference signals; demultiplexer means for demultiplexing said video signal in MAC format and said estimated color difference signals to thereby produce a video signal in non-MAC format; and marker means for generating a marker signal indicating that the video signal in non-MAC format has previously been MAC encoded, and for including said marker signal in said video signal in non-MAC format.

Claim 14

A MAC signal decoder for decoding a video signal which is in MAC format containing vertically sub-sampled color difference signals into a video signal in non-MAC format, said decoder comprising: interpolating means for interpolating between said vertically sub-sampled color difference signals to produce estimated color difference signals; demultiplexer means for demultiplexing said video signal in MAC format and said estimated color difference signals to thereby produce a video signal in non-MAC format; and marker means for generating a marker signal indicating that the video signal in non-MAC format has previously been MAC encoded, and for including said marker signal in said video signal in non-MAC format.

Claim 15

A decoder according to claim 11, wherein said demultiplexer means is operative to produce said video signal in non-MAC format including luminance information, and said marker means is operative to cause said marker signal to be contained in the luminance information of said video signal in non-MAC format.

Claim 16

A decoder according to claim 12, wherein said marker means is operative to cause said marker signal to be contained in a vertical blanking interval of said video signal in non-MAC format.

Claim 17

A decoder according to claim 13, wherein said demultiplexer means is operative to produce a 625 line video signal in non-MAC format, and wherein said marker means is operative to cause said marker signal to be included in line 21 of said 625 line video signal in non-MAC format.

Claim 18

A decoder according to claim 13, wherein said marker means is operative to include said marker signal in said vertical blanking interval in a form such that said marker signal will be visible if said vertical blanking interval is displayed.

Claim 19

A decoder according to claim 15, wherein said marker means is operative to include said marker signal in said video signal in non-MAC format in the form of a peak white level present during a predetermined interval of a line of said vertical blanking interval.

Claim 22

A method according to claim 17, wherein the step of including said marker signal in said video signal in non-MAC format comprises including said marker signal in luminance information thereof.

Claim 23

A method according to claim 18, wherein the step of including said marker signal in said video signal in non-MAC format comprises including said marker signal in a vertical blanking interval thereof.

Claim 24

A method according to claim 19, wherein said step of producing a video signal in non-MAC format comprises producing a 625 line video signal, and said step of including a marker signal in said video signal in non-MAC format comprises including said marker signal in line 21 of said 625 line video signal in non-MAC format.

Claim 25

A method according to claim 19, wherein the step of including said marker signal in said video signal in non-MAC format comprises including a marker signal which will be visible if said vertical blanking interval is displayed.

Claim 26

A method according to claim 21, wherein the step of including said marker signal in said video signal in non-MAC format comprises including said marker signal in the form of a peak white level present during a predetermined interval of a line of said vertical blanking interval.

Claim 27

Apparatus for recording a video signal in MAC format, comprising: an input terminal for receiving a video signal including a luminance signal and color difference signals and having a marker signal indicating previous MAC encoding of the information therein selectively associated therewith; vertical filter means for vertically filtering said color difference signals so as to limit their spectra to a band below a predetermined vertical frequency; vertical sub-sampling means for vertically sub-sampling the color difference signals filtered by said vertical filter means to produce vertically sub-sampled color difference signals, said vertical sub-sampling means being operative to sub-sample said color difference signals at a predetermined sub-sampling rate such that the Nyquist frequency of said vertically sub-sampled color difference signals is substantially the same as said predetermined vertical frequency; multiplexer means for multiplexing the vertically sub-sampled color difference signals with the luminance signal to produce a video signal in MAC format; detector means responsive to said marker signal for selectively inhibiting the operation of said vertical filter means to prevent vertical filtering of said color difference signals thereby; and means for recording said video signal in MAC format on a record medium.

Claim 28

Apparatus for recording a video signal in MAC format, comprising: an input terminal for receiving a video signal including a luminance signal and color difference signals and having a marker signal indicating previous MAC encoding of the information therein selectively associated therewith; vertical filter means for vertically filtering said color difference signals so as to limit their spectra to a band below a predetermined vertical frequency; vertical sub-sampling means for vertically sub-sampling the color difference signals filtered by said vertical filter means to produce vertically sub-sampled color difference signals, said vertical sub-sampling means being operative to sub-sample said color difference signals at a predetermined sub-sampling rate such that the Nyquist frequency of said vertically sub-sampled color difference signals is substantially the same as said predetermined vertical frequency; multiplexer means for multiplexing the vertically sub-sampled color difference signals with the luminance signal to produce a video signal in MAC format; detector means responsive to said marker signal for selectively inhibiting the operation of said vertical filter means to prevent vertical filtering of said color difference signals thereby; and means for recording said video signal in MAC format on a record medium.

Claim 29

The apparatus of claim 23, further comprising: means for reproducing a video signal in MAC format from said record medium to produce a reproduced video signal including vertically sub-sampled color difference signals; interpolating means for interpolating between the vertically sub-sampled color difference signals in said reproduced video signal to produce estimated color difference signals; demultiplexer means for demultiplexing said reproduced video signal and said estimated color difference signals to thereby produce a reproduced video signal in non-MAC format; and marker means for generating a marker signal indicating that the information in said reproduced video signal in non-MAC format had previously been MAC encoded, and for including said marker signal in said reproduced video signal.

Claim 30

Apparatus for reproducing a video signal in MAC format including vertically sub-sampled color difference signals and recorded on a record medium, and for converting the reproduced video signal in MAC format to a video signal in non-MAC format including a marker signal indicating that the information therein had previously been MAC encoded, comprising: means for reproducing said video signal in MAC format from said record medium to provide a reproduced video signal; interpolating means for interpolating between the vertically sub-sampled color-difference signals in said reproduced video signal to produce estimated color difference signals; demultiplexer means for demultiplexing said reproduced video signal and said estimated color difference signals to thereby produce said reproduced video signal in non-MAC format; and marker means for generating said marker signal indicating that the information in said reproduced video signal in non-MAC format had previously been MAC encoded, and for including said marker signal in said reproduced video signal in-MAC format.

Claim 31

Apparatus for reproducing a video signal in MAC format including vertically sub-sampled color difference signals and recorded on a record medium, and for converting the reproduced video signal in MAC format to a video signal in non-MAC format including a marker signal indicating that the information therein had previously been MAC encoded, comprising: means for reproducing said video signal in MAC format from said record medium to provide a reproduced video signal; interpolating means for interpolating between the vertically sub-sampled color-difference signals in said reproduced video signal to produce estimated color difference signals; demultiplexer means for demultiplexing said reproduced video signal and said estimated color difference signals to thereby produce said reproduced video signal in non-MAC format; and marker means for generating said marker signal indicating that the information in said reproduced video signal in non-MAC format had previously been MAC encoded, and for including said marker signal in said reproduced video signal in-MAC format.