Abstract: The invention provides a method for coding an output bitstream of an input video so the decoded output bitstream has a constant perceived quality. A base layer bitstream having a constant bit-rate is generated from the input video, and an input enhancement layer bitstream is generated from a difference between the input video and the base layer bitstream. Alternatively, the base and input enhancements layer bitstreams are pre-stored.

Abstract: The apparatus for decoding a digital signal includes a composite picture forming unit for forming a composite picture from a first digital video signal and a second digital video signal. The first digital video signal includes inter-coded picture data. A down-converter receives a third digital video signal, and outputs the third digital video signal to the composite picture forming unit as the first digital signal in a first mode. However, the down-converter down-converts the third digital video signal into a fourth digital video signal in a second mode, and outputs the fourth digital video signal to the composite picture forming unit in the second mode. A memory stores the anchor pictures output from the composite picture forming unit, and a motion compensator generates the second digital signal based on the stored anchor pictures.

Abstract: A method describes activity in a video sequence. The method measures intensity, direction, spatial, and temporal attributes in the video sequence, and the measured attributes are combined in a digital descriptor of the activity of the video sequence.

Abstract: A method transcodes groups of macroblocks of a partially decoded input bitstream. The groups of macroblocks include intra-mode and inter-mode macroblocks. Each macroblock includes DCT coefficients, and at least one motion vector. The modes of each group of macroblocks are mapped to be identical only if there is an inter-mode block and an intra-mode macroblock in the group. If any of the macroblocks in the group are mapped, then the DCT coefficients and the motion vector for such mapped macroblocks are modified in accordance with the mapping to generate reduced-resolution macroblock for an output compressed bitstream to compensate for drift.

Abstract: A method encodes a video a video objects. For each candidate object, a quantizer parameter and a skip parameter that jointly minimizes an average total distortion in the video are determined while satisfying predetermined constraints. The average total distortion includes spatial distortion of coded objects and spatial and temporal distortion of uncoded objects. Then, the candidate objects is encoded as the coded objects with the quantizer parameter and the skip parameter, and the candidate objects is skipped as the uncoded objects with the skip parameter.

Abstract: A compressed bitstream is scaled down to a reduced rate bitstream by first demultiplexing a compressed input bitstream to extract video objects as elementary input bitstreams having a first bit rate. A transcoder converts each elementary input bitstream to an elementary output bitstream having a second bit rate. The first bit rate is less than the second bit rate. A transcoding control unit, coupled to the transcoder, supplies control information for the transcoder. A multiplexer composes the elementary output bitstreams into a compressed output bitstream having the second bit rate.

Abstract: A method and system reduces the spatial resolution of a compressed bitstream of a sequence of frames of a video signal by first decoding the frames, and storing the decoded frames in a first frame buffer. While performing the decoding, motion compensating is performed with full resolution motion vectors of the stored decoded frames. The decoded frames are then down-sampled to a reduced resolution, and stored in a second frame buffer. The reduced resolution frames are partially encoded to produce a reduced resolution compressed bitstream of the video. While performing the partial encoding, motion compensation is performed with reduced resolution motion vectors of the stored reduced resolution frames.

Abstract: A method determines distortion in a video by measuring a spatial distortion in coded frames, and by measuring a temporal distortion and spatial distortion in uncoded frames. The spatial distortion of the coded frames is combined with the temporal distortion and the spatial distortion of the uncoded frames to determine a total average distortion in the video.

Abstract: In an apparatus for transcoding a compressed video, a generator simulates constraints of a network and constraints of a user device. A classifier is coupled to receive an input compressed video and the constraints. The classifier generates content information from features of the input compressed video. A manager produces a plurality of conversions modes dependent the constraints and content information, and a transcoder produces output compressed videos, one for each of the plurality conversion modes.

Abstract: A method manages traffic over a channel of a network connecting a sender end system and a receiver end system. The traffic includes multimedia packets. The channel is modeled as a queue having an associated queue occupancy. The times when packets are sent and the times when feedback messages are received are maintained in the sender end system. A time series of samples for a service time experienced by each packet sent is updated based on the total number of packets sent and the total number of feedback messages received. A queue occupancy for a next packet to be sent is then predicted based on the time series, and the next packet is sent according to the predicted queue occupancy.

Abstract: A method compensates for drift in macroblocks of a partially decoded input bitstream. The macroblocks include intra-mode and inter-mode macroblocks, and each macroblock includes DCT coefficients, and at least one motion vector. An estimate of drift is measured in the partially decoded input bitstream. The estimated drift is translated into an intra refresh rate. The modes of inter-mode macroblock are mapped to inter-mode macroblock according to the refresh rate. The DCT coefficients and the motion vector for each changed macroblock are modified in accordance with the mapping for each changed macroblock.

Abstract: This invention relates to methods of abrupt scene change detection and fade detection for indexing of MPEG-2 and MPEG-4 compressed video sequences. Abrupt scene change and fade-detection techniques applied to signals in compressed form have reasonable accuracy and the advantage of high simplicity since they are based on entropy decoding and do not require computationally expensive inverse Discrete Cosine Transformation (DCT).

Abstract: A method determines a surface of an object in a sequence of images. The method begins by estimating a boundary of the object in each image of the sequence using motion information of adjacent images of the sequence. Then, portions of each image of the sequence are ordered to produce an ordered sequence of images. The ordered portions are exterior to the estimated object boundary. Edges in each ordered image are filtered using the motion information, and each ordered image of the sequence is searched to locate the filtered edges to form a new boundary outside the estimated boundary. The filtering and searching are repeated, while projecting the new object boundaries over the sequence of images, until the new object boundaries converges to a surface of the object.

Abstract: A method locates scene changes in a sequence of images or frames that have been compressed without first decompressing the sequence. The sequence includes subsequences of P-frames between I-frames. DC residual coefficients including sign information are extracted from the sub-sequences of P-frames. If the number of residual coefficients in the P-frames exceed a predetermined threshold, then a scene change is indicated. Positive coefficients indicate fade-ins, and negative coefficients indicate fade-outs.

Abstract: A method represents a shape of an object in an image. Portions of the image interior to a boundary of the object are ordered. A medial axis for the ordered portions of the image is derived. The medial axis is segmented to produce an ordered tree. The ordered tree is transformed to a partial ordered tree to represent the shape of the object.

Abstract: A method detects a boundary in a sequence of two-dimensional images where each image has multiple intensity value points. Filtering and motion analysis is applied on each image to produce motion enhanced images. Initial search parameters are determined from a dynamic snake model applied to the motion enhanced images. Each motion enhanced image is searched for a potential boundary using the search parameters. The potential boundary is projected into the motion enhanced image of a previous, current, and next image, and the search parameters of the previous, current, and next images are updated. The searching, projecting, and updating repeat until a predetermined level of convergence is reached.

Abstract: A method determines true motion vectors associated with a sequence of images. The images include fields made up of blocks of pixels. The method selects candidate feature blocks from the blocks of pixels. The candidate feature blocks have intensity variances above a threshold indicative of texture features. Candidate feature blocks in similarly numbered adjacent field intervals are compared to determine sets of displaced frame differences parameters for each candidate feature block. The true motion vectors for each candidate feature block are determined from a minimum weighted score derived from the difference parameters.

Abstract: An apparatus and concomitant method for selecting a macroblock coding mode based upon the quantization scale selected for the macroblock. The total number of bits needed to code each macroblock consists of two parts, bits needed for coding motion vectors and bits for coding the predictive residual. The number of bits for coding the motion vectors is generally obtained from a look-up table. The number of bits for coding the predictive residual is obtained by an estimation which assumes that the number of bits for encoding the predictive residuals is directly proportional to the value of its variance and inversely proportional to the value of quantizer steps (quantizer scale). Using this estimation, the total number of bits necessary to code a macroblock is calculated and compared for each coding mode. By selecting the coding mode with the least number of bits, a near-optimal solution of low complexity for practical implementation is acquired.

Abstract: A method and apparatus for selecting a quantizer scale for each macroblock to maintain the overall quality of the video image while optimizing the coding rate. A quantizer scale is selected for each macroblock such that target bit rate for the picture is achieved while an optimal quantization scale ratio is maintained for successive macroblocks to produce a uniform visual quality over the entire picture. One embodiment applies the method to the frame level while another embodiment applies the method in conjunction with a wavelet transform.

Abstract: A digital video decoder and method therefor receives a digital video signal and performs motion compensation on the digital video signal in the frequency domain. The motion compensation is performed by forming, for each inter-coded picture in the digital video signal, a composite picture in the frequency domain representing a reference picture corresponding to the inter-coded picture, and then adding the composite picture to the corresponding inter-coded picture. Each macro block of the composite picture is formed based on corresponding macro blocks of at least one anchor picture stored in memory. The anchor pictures are stored as compressed bits via quantization and variable length coding of frequency domain blocks to reduce required memory capacity. The synthesis technique employed by the compositor to form the composite macro blocks accounts for both field and frame motion compensation with half-pel accuracy.