Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1998-03-13
2001-02-27
Kelley, Chris S. (Department: 2713)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
Reexamination Certificate
active
06195390
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention related to a picture signal encoding apparatus for compression-coding picture signals and a picture signal decoding apparatus for expansion-decoding compression-coded picture signals.
2. Description of the Related Art
A digital video tape recorder (VTR) is used as means for recording/reproducing picture signals of a television broadcasting program or the like. There are several formats of the digital VTR, such as, the d1 standard for program production and the d2 standard for broadcasting stations. With respect to such digital VTR for program production or for broadcasting stations, since extremely high quality is required of pictures to be recorded/reproduced, it is normal that picture signals to be recorded onto a magnetic tape are not compressed, or that a relatively low compression rate for compressing the data quantity to approximately ½ is used.
Meanwhile, the digital VTR for commercial use is becoming broadly used. The digital VTR for commercial use needs to enable long-time recording using a compact cassette tape, though the requirement of picture quality is lower than that of the digital VTR for business use. Therefore, a compression format for performing band compression at a relatively high compression rate for compressing the picture data quantity to approximately ⅕ is employed. The compression format of the digital VTR for commercial use provides high picture quality, and therefore used also for video equipments for broadcasting business. The high-efficiency compression method used here utilizes the fact that the human visual characteristic is less sensitive to color-difference information than to luminance information of a picture, and therefore, the information amount of color-difference signals is reduced. This picture data compression method will be described later.
In accordance with the above-described D1 standard as a digital VTR standard for program production or for broadcasting stations, digital picture data to be recorded onto a magnetic tape are not compressed, and a luminance signal Y and color-difference signals Cr, Cb are separately recorded. The color-difference signals are signals obtained by removing the luminance signal Y from three primary colors of R, G and B. As the color-difference signals, two signals of Cr=R−Y and Cb=B−Y are employed. For example, the sampling frequency of the luminance signal Y is 13.5 MHz and the sampling frequency of each of the color-difference signals Cb, Cr is 6.75 MHz. Therefore, the ratio of sampling frequency of these signals is 4:2:2.
On the other hand, with respect to picture data in conformity to the above-described digital VTR standard for commercial use, the sampling frequency ratio of the luminance signal Y and the color-difference signals Cb, Cr is expressed as 4:1:1 in the NTSC system (with 525 lines) or 4:2:0 in the PAL system (with 625 lines). That is, by reducing the sampling frequency of the two color-difference signals to half the sampling frequency of the luminance signal, the information amount of picture data to be recorded on a magnetic tape is reduced. Thus, in accordance with the digital VTR standard for commercial use, a signal is generated such that the band of a chroma signal of a base band signal is narrowed, and digital compression by intra-frame DCT is carried out to compress the picture data quantity to approximately ⅕ for recording.
As described above, the picture data compression systems (formats) which differ from one another are used for the digital VTR, and there is no digital VTR which can handle plural data compression formats. Therefore, for example, when the compressed picture data of 4:1:1 and the compressed picture data of 4:2:2 as described above are to be edited, editing operation must be carried out after temporarily expanding either one of the compressed picture data, and deterioration in picture quality generated in re-compressing the edited picture data cannot be avoided.
In addition, with respect to the digital VTR for broadcasting business in which high picture is required, higher picture quality exceeding the performance of the conventional digital VTR is required in some cases. For example, a base band of 4:2:2 is required, or a picture having less compression noise is required. Also, with respect to the digital VTR for commercial use, adoption of a standard for higher picture quality is expected.
SUMMARY OF THE INVENTION
It view of the foregoing status of the art, it is an object of the present invention to provide a picture signal encoding apparatus and a picture signal decoding apparatus which have compatibility between picture data of 4:1:1 or 4:2:0 in conformity to the format of the conventional digital picture data and high-quality picture data of 4:2:2.
According to the present invention, there is provided a picture signal encoding apparatus for compression-coding picture signals, the apparatus including: first compression coding means for converting and compression-coding basic picture signals having a sampling frequency ratio of a luminance signal and two color-difference signals of 4:2:2 to have a sampling frequency ratio of the luminance signal and the two color-difference signals of 4:1:1 or 4:2:0 so as to generate first compressed data; encoding residual extracting means for extracting an encoding residual between the basic picture signals and the compressed data; and second compression coding means for compression-coding the extracted encoding residual so as to generate second compressed data.
According to the present invention, there is also provided a picture signal decoding apparatus for expansion-decoding compression-coded picture signals, the apparatus including: first expansion decoding means for expansion-decoding basic picture data of a predetermined signal standard having a sampling frequency ratio of a luminance signal and two color-difference signals of 4:1:1 or 4:2:0, the basic picture data being generated by compression-coding original picture signals; second expansion decoding means for expansion-decoding enhancement data having a sampling frequency ratio of a luminance signal and two color-difference signals of 4:2:2; and synthesizing means for synthesizing outputs from the first expansion decoding means and the second expansion decoding means so as to generate extended picture data having a sampling frequency ratio of a luminance signal and two color-difference signals of 4:2:2.
According to the present invention, there is also provided a picture signal encoding apparatus for compression-coding picture signals, the apparatus including: converting means for converting the picture signals having a sampling frequency ratio of a luminance signal and two color-difference signals of 4:2:2 to basic picture signals having a sampling frequency ratio of a luminance signal and two color-difference signals of 4:1:1 or 4:2:0; first compressing means to which the basic picture signals converted by the converting means are inputted, the first compressing means being adapted for carrying out first compression so as to output first compressed data; encoding residual extracting means for extracting an encoding residual between the basic picture signals before compression and signals generated by decoding the compressed data; and second compressing means to which data indicating the extracted encoding residual is inputted, the second compressing means being adapted for outputting second compressed data generated by carrying out predetermined compression of the data.
According to the present invention, there is further provided a picture signal decoding apparatus for decoding compressed picture signals, the apparatus including: first decoding means for decoding compressed first picture signals having a sampling frequency ratio of a luminance signal and two color-difference signals of 4:1:1; second decoding means for decoding compressed second picture signals having a sampling frequency ratio of a luminance signal and two color-difference signa
Hashino Tsukasa
Hayakawa Tomoo
Nagasawa Fumihiro
Takiduka Hiroshi
Frommer William S.
Frommer & Lawrence & Haug LLP
Kelley Chris S.
Shallenburger Joe H.
Sony Corporation
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