Video signal processing apparatus, for controlling contrast compensation and edge compensation in relation to each other in depedence on luminance of an image, and television receiver including the same

1. A video signal processing apparatus comprising:

a contrast compensation unit for compensating contrast of a video signal;

an edge compensation unit for compensating an edge portion of the video signal; and

a control circuit for controlling the contrast compensation unit and the edge compensation unit on the basis of luminance information of the video signal,

wherein said control circuit determines a gradation range in which image quality is compensated on the basis of the luminance information of the video signal, and controls said contrast compensation unit so that the contrast of the video signal belonging to the luminance range thus determined is made higher than that of the video signal belonging to another luminance range, and also controls said edge compensation unit so that an edge compensation quantity for the video signal belonging to the luminance range thus determined is made smaller than that in the video signal belonging to another gradation range.

2. A video signal processing apparatus comprising:

a detection unit for counting a number of pixels in each of a plurality of predetermined gradation ranges on the basis of a video signal applied thereto so as to obtain a histogram indicative of luminance distribution during a preset time period of the video signal;

a contrast compensation unit for compensating contrast of the video signal;

an edge compensation unit for compensating an edge portion of the video signal; and

a control unit for controlling said contrast compensation unit and said edge compensation unit on the basis of the histogram obtained from the detection unit,

wherein said control unit determines a gradation range in which the number of pixels are made greater than a preset threshold value in the histogram obtained from the detection unit, and controls said contrast compensation unit so that contrast for the video signal applied thereto corresponding to the gradation range thus determined is made higher than that of the video signal corresponding to another gradation range, and also controls said edge compensation unit so that an edge compensation quantity for the video signal corresponding to the gradation range thus determined is made smaller than that of the video signal corresponding to another gradation range.

3. A video signal processing apparatus according to claim 2 , wherein the preset time period in the video signal is a time period corresponding to one frame of the video signal.

4. A video signal processing apparatus according to claim 2 , wherein said detection unit detects pixels having a luminance level lower than a predetermined luminance level, and said control unit controls the compensation quantity of said edge compensation circuit on the basis of the detection result.

5. A video signal processing apparatus according to claim 2 , wherein said edge compensation unit comprises a filter circuit for extracting a signal of an edge portion from the video signal, a coring circuit for conducting coring on the edge signal outputted from the filter circuit, and a gain control circuit for controlling a gain for the edge signal subjected to coring in the coring circuit.

6. A video signal processing apparatus according to claim 5 , wherein said control unit controls the edge compensation quantity by controlling a coring quantity in the coring circuit.

7. A video signal processing apparatus according to claim 5 , wherein said control unit controls the edge compensation quantity by controlling a gain in the gain control circuit.

8. A video signal processing apparatus according to claim 2 , wherein after edge compensation conducted by said edge compensation unit, contrast compensation is conducted by said contrast compensation unit.

9. A video signal processing apparatus according to claim 2 , wherein after contrast compensation conducted by said contrast compensation unit, edge compensation is conducted by said edge compensation unit.

10. A television receiver comprising:

a contrast compensation unit for compensating contrast of a video signal;

an edge compensation unit for compensating an edge portion of the video signal;

a control circuit for controlling said contrast compensation unit and said edge compensation unit on the basis of luminance information of the video signal; and

a display unit of pixel selection type for displaying an image based on the video signal which is compensated in contrast by said contrast compensation unit and compensated in edge by said edge compensation unit,

wherein said control circuit determines a gradation range in which image quality is compensated on the basis of luminance information of the video signal, and controls said contrast compensation unit so that contrast of the video signal belonging to the luminance range thus determined is made higher than that of the video signal belonging to another luminance range, and also controls said edge compensation unit so that edge compensation quantity for the video signal belonging to the luminance range thus determined is made smaller than that of the video signal belonging to another gradation range.

11. A television receiver comprising:

a detection unit responsive to a video signal applied thereto for counting a number of pixels belonging to each of a plurality of predetermined gradation ranges so as to obtain a histogram indicative of luminance distribution of the video signal in a preset time period;

a contrast compensation unit for compensating contrast of the video signal;

an edge compensation unit for compensating an edge portion of the video signal;

a control unit for controlling said contrast compensation unit and said edge compensation unit on the basis of the histogram obtained from said detection unit; and

a display unit of pixel selection type for displaying an image based on the video signal which is compensated in contrast by said contrast compensation unit and compensated in edge by said edge portion compensation unit

wherein said control unit determines a gradation range in which the number of pixels thus counted are made larger than a preset threshold value in the histogram obtained from said detection unit, and controls said contrast compensation circuit so that contrast for the video signal applied thereto corresponding to the luminance range thus determined is made higher than that of the video signal corresponding to another gradation range, and also controls said edge compensation unit so that an edge compensation quantity for the applied video signal corresponding to the gradation range thus determined is made smaller than that of the video signal corresponding to another gradation range.

12. A video signal processing apparatus comprising:

a detection unit for counting a number of pixels in each of a plurality of predetermined gradation ranges on the basis of a video signal applied thereto so as to obtain a histogram indicative of luminance distribution during a preset time period of the video signal;

a contrast compensation unit for compensating contrast of the video signal;

an edge compensation unit for compensating an edge portion of the video signal; and

a control unit for controlling said contrast compensation unit and said edge compensation unit on the basis of the histogram obtained from the detection unit,

wherein said control unit determines a gradation range in which the number of pixels are made greater than a preset threshold value in the histogram obtained from the detection unit, and controls said contrast compensation unit so that contrast for the video signal applied thereto corresponding to the gradation range thus determined is made higher than that of the video signal corresponding to another gradation range, and also controls said edge compensation unit so that an edge compensation quantity for the video signal corresponding to the gradation range thus determined is made smaller than that of the video signal corresponding to another gradation range, and

wherein after edge compensation conducted by said edge compensation unit, contrast compensation is conducted by said contrast compensation unit.