Video coder providing implicit coefficient prediction and scan adaptation for image coding and intra coding of video

A video coding method, comprising:

• coding blocks of image data according to a discrete cosine transform,
• quantizing coded blocks of the image data, and
• for a first quantized block of coded image data:
• determining a horizontal gradient among DC coefficients of a second quantized block and a third quantized block, wherein the second quantized block is above the first quantized block and the third quantized block is adjacent to the second quantized block,
• determining a vertical gradient among DC coefficients of the third quantized block and a fourth quantized block below the third quantized block,
• selecting one of the second and fourth quantized blocks as a source block based on a comparison of the horizontal and vertical gradients,
• predicting a DC coefficient of the first quantized block from the source block and,
• generating a DC residual representing a difference between an actual DC coefficient and the predicted DC coefficient.

A video coding method, comprising:

• coding blocks of image data according to a discrete cosine transform,
• quantizing the coded blocks of the image data,
• for a first quantized block of coded image data:
• determining a horizontal gradient among DC coefficients of a second quantized block and a third quantized block, wherein the second quantized block is above the first quantized block and the third quantized block is adjacent to the second quantized block,
• determining a vertical gradient among DC coefficients of the third quantized block and a fourth quantized block below the third quantized block,
• selecting one of the second and fourth quantized blocks as a source block based on a comparison of the horizontal and vertical gradients,
• predicting a DC coefficient of the first quantized block from the source block and,
• substituting for the DC coefficient of the first quantized block a DC residual representing a difference between the DC coefficient of the first quantized block and the predicted DC coefficient;
• and
• run length encoding the first quantized block.

A coded data signal generated according to the process of:

• coding block of image data according to a discrete cosine transform,
• for a first block of coded image data:
• determining a horizontal gradient among DC coefficients of a second block and a third block, wherein the second block is above the first block and the third block is adjacent to the second block,
• determining a vertical gradient among DC coefficients of the third block and a fourth block below the third block,
• selecting one of the second and fourth blocks as a source block based on a comparison of the horizontal and vertical gradients,
• predicting a DC coefficient of the first block from the source block and,
• substituting for the DC coefficient of the first block a DC residual coefficient representing a difference between the DC coefficient of the first block and the predicted DC coefficient;
• run length coding the DC residual coefficient and remaining data of the first block, and
• outputting the run length coded data coefficients in the coded data signal.