Digital stream transcoder with a hybrid-rate controller
AssigneeScientific-Atlanta, Inc.
InventorJoel W. Schoenblum
Life of this patent
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Abstract
A rate controller in a transcoder, which receives a stream of compressed frames carried in a bit stream, selectively determines whether to quantize and/or threshold slices of a frame carried in the stream of frames. The rate controller determines the input size of the frame and based at least in part upon at least a desired size, requantizes and/or thresholds the frame such that the output size of the frame is approximately the desired size.
Claims51
A method of transcoding a digital stream of compressed frames, the method comprising the steps of:
- (a) receiving a compressed video frame having content information and non-content information included therein;
- (b) determining the total compressed size of the frame (NT);
- (c) determining from at least the total compressed size of the frame the total number of bits (NS) to shave from the compressed frame;
- (d) determining a plurality of statistics about a given portion of the frame;
- (e) determining whether to requantize the given portion based at least in part upon at least one of the statistics about the given portion;
- (f) responsive to determining to requantize the given portion, requantizing the levels of the given portion;
- (g) determining whether to threshold the given portion based at least in part on the at least one of the statistics about the given portion;
- (h) responsive to determining to threshold the given portion, thresholding the levels of the given portion;
- and
- (i) transmitting the given portion.
An apparatus in a network for transcoding a digital stream of compressed frames, the apparatus comprising:
- a decoder adapted to decompress a video frame having content information and non-content information included therein into the DCT-domain, wherein the content-information carried by the frame is represented as levels in the DCT-domain;
- a rate controller adapted to receive the video frame, parse the video frame into a plurality of portions, determine a plurality of statistics about a given portion, and determine a target number of bits to shave (N_shave) from the given portion;
- a requantizer adapted to requantize levels of the given portion;
- a thresholder adapted to threshold the given portion, wherein the rate controller determines whether the given portion should be requantized and whether the given portion should be thresholded based at least in part on at least one of the statistics about the given portion;
- and
- an encoder adapted to compress the frame, wherein the compressed size of the frame is approximately the same as a target size.
Dependencies are inferred from the claim text.