Dynamic dithering for video compression

A method for dithering video and dithering information transmitted from a custom encoder over a communication channel, comprising:

• (a) selecting a segment of video frames from the video;
• (b) computing a noise map for the segment of the video, the noise map computed from differences among pixels selected from spatially-distributed sampling patterns in the segment;
• (c) determining contours of quantization artifacts within the video frame based on the noise map and a histogram of pixel values in the video frame;
• (d) computing a gradient measurement of pixel values along the contours;
• (e) identifying regions along the contours of quantization artifacts to apply dithering based on the noise map and the gradient measurement;
• (f) determining a dithering strength based on the noise map and the gradient measurement;
• (g) transmitting the bitstream and dithering information over the communication channel to a decoder, the dithering information including the contours of quantization artifacts, the identified regions along the contours, and the determined dithering strength.

A method for dithering video to be encoded in an encoder, comprising:

• selecting a segment of video frames from the video;
• computing a noise map for the segment of the video, the noise map computed from differences among pixels selected from spatially-distributed sampling patterns in the segment;
• determining contours of quantization artifacts within the video frame based on the noise map and a histogram of pixel values in the video frame;
• computing a gradient measurement of pixel values along the contours;
• identifying regions along the contours of quantization artifacts to apply dithering based on the noise map and the gradient measurement;
• determining a dithering strength based on the noise map and the gradient measurement;
• applying dithering noise to the identified regions at the determined dithering strength along the identified regions, and
• encoding the dithered video at the encoder.

A device for dithering a video, comprising:

• a processor configured to perform:
• selecting a segment of video frames from the video;
• computing a noise map for the segment of the video, the noise map computed from differences among pixels selected from spatially-distributed sampling patterns in the segment;
• determining contours of quantization artifacts within the video frame based on the noise map and a histogram of pixel values in the video frame;
• computing a gradient measurement of pixel values along the contours;
• identifying regions along the contours of quantization artifacts to apply dithering based on the noise map and the gradient measurement;
• determining a dithering strength based on the noise map and the gradient measurement;
• and
• applying dithering noise to the identified regions at the determined dithering strength along the identified regions.

A machine-readable medium stored thereon codes configured to perform a method for dithering video from a decoder, comprising:

• selecting a segment of video frames from the video;
• computing a noise map for the segment of the video, the noise map computed from differences among pixels selected from spatially-distributed sampling patterns in the segment;
• determining contours of quantization artifacts within the video frame based on the noise map and a histogram of pixel values in the video frame;
• computing a gradient measurement of pixel values along the contours;
• identifying regions along the contours of quantization artifacts to apply dithering based on the noise map and the gradient measurement;
• determining a dithering strength based on the noise map and the gradient measurement;
• and
• applying dithering noise to the identified regions at the determined dithering strength along the identified regions.

A method for dithering video from a decoder, comprising:

• computing directional shift differences for a video frame;
• determining contours of quantization artifacts in the video frame based on the directional shift differences and a histogram of pixel values in the video frame;
• computing a gradient measurement of pixel values along the contours;
• identifying regions along the contours of quantization artifacts to apply dithering based on the gradient measurement;
• determining a dithering strength based on the gradient measurement;
• and
• applying dithering noise to the identified regions at the determined dithering strength along the identified regions.