1. A method implementable on an encoder for adjusting a coding threshold for encoding a block in an image, wherein the coding threshold determines whether the block should be coded, comprising: encoding, at a first time, a first image representation of the block using first encoding parameters generated by the encoder; encoding, at a second time later than the first time, a second image representation of the block using second encoding parameters generated by the encoder; assessing at least the first and second encoding parameters to determine whether the image is likely stationary, wherein the first and second encoding parameters comprise at least first and second quantization parameters; and if the image is likely stationary, adjusting the coding threshold in the encoder for at least a portion of the block.