Video coding and decoding method

A video coding method for image communication, comprising:

• a communication limit condition setting step of setting a specified reference compression ratio;
• a video compressing step of compressing a present image changing a compression ratio according to a transmission rate;
• a step of comparing a present compression ratio of the compressed image with the set reference compression ratio;
• and
• a step of performing compensation value control with respect to an image obtained before the compression to lower a complexity of the image if the present compression ratio of the compressed image is larger than the reference compression ratio and performing the above compression with respect to the compensation value controlled image,
• wherein said compensation valve control is achieved by a color signal processing operation including,
• a color clamp compensation step of compensating a level of the color signal;
• an automatic white balance control step of automatically controlling RGB components of the compensated color signal;
• a color gamma transformation step of replacing data to make the RGB controlled video signal comport with color brightness of a display device;
• and
• a chroma suppress compensation step of decreasing a size of the replaced color data depending on a size of luminance contour and a low illumination.

A video coding method for an image communication system, the method comprising the steps of:

• setting, as a limit condition of image communication, a maximum data size (Max_Data) per frame in accordance with a video transmission rate and a reference compression ratio available;
• compressing a present image and comparing a data size of the compressed video data with the set maximum data size;
• performing compression changing the compression ratio of a source image until the size of the present compressed video data is smaller than the set maximum data size if the size of the present compressed video data is larger than the maximum data size;
• comparing a present compression ratio of the compressed image with the set reference compression ratio if the data size of the present compressed image is smaller than the maximum data size;
• compensating the present image to lower its complexity and repeating the above steps starting from the compression step if the present compression ratio is larger than the reference compression ratio;
• and
• transmitting the present compressed image if the present compression ratio is smaller than the reference compression ratio,
• wherein the present image is compensated by performing a luminance signal process operation,
• said luminance signal processing operation including,
• a luminance signal clamp compensation step of compensating a value of luminance level of an incoming CCD (charge coupled device) digital video signal;
• a horizontal/vertical contour compensation step of extracting data of a contour part from the compensated video signal and compensating the horizontal/vertical contour;
• and
• a low luminance signal compensation step of compensating the horizontal/vertical contour compensated video signal for a low data value of low luminance.

A video decoding method for an image communication system, the method comprising:

• an overhead reading step of detecting from a received data bitstream, information indicating whether or not contour compensation was performed and which of emphasizing and attenuating compensations was performed, wherein the compensations include a luminance signal processing operation having,
• a luminance signal clamp compensation- step of compensating a value of luminance. level of an incoming CCD (charge coupled device) digital video signal;
• a horizontal/vertical contour compensation step of extracting data of a contour part from the compensated video signal and compensating the horizontal/vertical contour;
• and
• a low luminance signal compensation step of compensating the horizontal/vertical contour compensated video signal for a low data value of low luminance;
• a contour compensation step of performing the contour compensation with respect to the received video data if it is determined that the received video data was not contour-compensated or the attenuating compensation was performed with respect to the received video data according to a result of said overhead reading step;
• and
• a step of reconstructing the received video data as it is without performing the compensation if it is determined that the contour emphasizing compensation was performed with respect to the received data according to the result of said overhead reading.

A video coding method for an image communication system, the method comprising the steps of:

• setting, as a limit condition of image communication, a maximum data size (Max13 Data) per frame in accordance with a video transmission rate and a reference compression ratio available;
• compressing a present image and comparing a data size of the compressed video data with the set maximum data size;
• performing compression changing the compression ratio of a source image until the size of the present compressed video data is smaller than the set maximum data size if the size of the present compressed video data is larger than the maximum data size;
• comparing a present compression ratio of the compressed image with the set reference compression ratio if the data size of the present compressed image is smaller than the maximum data size;
• compensating the present image to lower its complexity and repeating the above steps starting from the compression step if the present compression ratio is larger than the reference compression ratio;
• and
• transmitting the present compressed image if the present compression ratio is smaller than the reference compression ratio,
• wherein the present image is compensated by a color signal processing operation including,
• a color clamp compensation step of compensating a level of the color signal;
• an automatic white balance control step of automatically controlling RGB components of the compensated color signal;
• a color gamma transformation step of replacing data to make the RGB controlled video signal comport with color brightness of a display device;
• and
• a chroma suppress compensation step of decreasing a size of the replaced color data depending on a size of luminance contour and a low illumination.

A video decoding method for an image communication system, the method comprising:

• an overhead reading step of detecting from a received data bitstream, information indicating whether or not contour compensation was performed and which of emphasizing and attenuating compensations was performed, wherein the compensations include a color signal processing operation including,
• a color clamp compensation step of compensating a level of the color signal;
• an automatic white balance control step of automatically controlling RGB components of the compensated color signal;
• a color gamma transformation step of replacing data to make the RGB controlled video signal comport with color brightness of a display device;
• and
• a chroma suppress compensation step of decreasing a size of the replaced color data depending on a size of luminance contour and a low illumination;
• a contour compensation step of performing the contour compensation with respect to the received video data if it is determined that the received video data was not contour-compensated or the attenuating compensation was performed with respect to the received video data according to a result of said overhead reading step;
• and
• a step of reconstructing the received video data as it is without performing the compensation if it is determined that the contour emphasizing compensation was performed with respect to the received data according to the result of said overhead reading.