Stmicroelectronics S.r.l.

U.S. Philips Corporation

Daniele Bagni

Fabrizio Simone Rovati

Daniele Alfonso

Luca Pezzoni

Danilo Pietro Pau

Davide Giovenzana

Bruno Biffi

Maria Luisa Sacchi

Luca Battistelli

Stefano Tono

Mattia De Bei

Flavio Benussi

Gian Antonio Mian

In an embodiment, a method for converting an input video sequence, comprising digital images organized in frames and operating at a variable frame-rate, into an output video sequence, operating at a pre-set constant frame-rate, storing the input video sequence temporarily and controlling fetching of images of said temporarily stored input video sequence. The method further includes controlling fetching of images from the temporarily stored input video sequence by adjusting an emptying rate to form an intermediate video sequence; and carrying out an operation of motion-compensated interpolation on the intermediate video sequence to form the output video sequence operating at a pre-set constant frame-rate, the emptying rate being adjusted as a function of a number of images of the input video sequence with variable frame-rate temporarily stored. An application is in the reproduction of video sequences in mobile terminals, with the capacity of audio-video conversation, for example for videoconferences.

Method for the frame-rate conversion of a video sequence of digital images, related apparatus and computer program product

In an embodiment of a method for converting an input video sequence, comprising digital images organized in frames and operating at a variable frame-rate, into an output video sequence, operating at a pre-set constant frame-rate, it is envisaged to store the input video sequence temporarily and to control fetching of images of said temporarily stored input video sequence. The method moreover envisages: 

A method for controlling the bit-rate of a bitstream of encoded video signals at a variable bitrate, the bitstream being generated by compressing a video sequence of moving pictures, wherein each picture comprises a plurality of macroblocks of pixels compressed by any of transform coding, temporal prediction, bi-dimensional motion compensated interpolation or combinations thereof, to produce any of I and/or P and/or B frames, the method involving quantization of said macroblocks effected as a function of a quantization parameter. The method includes defining a target bit-rate as well as maximum positive and negative error values between the target bit-rate and an average value of the current bit-rate of the bitstream, controlling the current bit-rate in order to constrain it between said maximum positive and negative error values, and defining an allowed range of variation for updating at least one reference parameter representative of the average value of the quantization parameter over each picture, wherein said allowed range is determined as a function of the target bit-rate and the maximum positive and negative error values.

Method and apparatus for variable bit-rate control in video encoding systems and computer program product therefor

A method of processing a bitstream of coded data of video sequences of progressive or interlaced pictures includes estimating motion vectors of groups of pixels. These groups of pixels belong to a top half-frame of the current picture in relation to pixels belonging to a bottom half-frame of a preceding picture. Motion vectors are also estimated for group of pixels of a bottom half-frame of the current picture in relation to pixels belonging to the top half-frame of the current picture. The processing calculates for each macroblock of a top half-frame and a bottom half-frame a respective top motion coefficient and a bottom motion coefficient depending on the estimation of the motion vectors of the top half-frame and the bottom half-frame. The current picture is recognized as an interlaced picture by a substantial equality of the distributions of values of the motion coefficients, or as a progressive picture by a substantial inequality of the distributions of values of the motion coefficients.

Processing of motion vector histograms for recognizing the interleaved or progressive character of pictures

Through a comparison of the values of pixels of a first candidate predictor macroblock having pixels in homologous positions to those of a reference macroblock of identical position on the frame to that of the macroblock being estimated on a reference frame of the present sequence of picture frames, a pre-established cost function is evaluated for each comparison. The best predictor is the one producing the minimum value of cost function. The comparison may even include the summing to each predictor candidate of an update vector of smaller dimensions than the macroblocks, chosen among a plurality of pre-established update vectors, for accelerating the convergence process of the comparison.

Spatio-temporal recursive motion estimation with 1/2 macroblock and 1/4 pixel undersampling

The compression and coding of digital data pertaining to video sequences of pictures including motion estimation for removing temporal redundance are provided by recognizing the occurrence of a change of a scene to control the prediction computation of the pictures. This control is provided using a forward motion estimation for pictures preceding the change of scene, and using a backward motion estimation for pictures subsequent the change of scene of a given sequence. A change of a scene is reliably detected by checking two distinct indexes. These indexes are based on an average value of a smoothness index of the preestablished number of last processed pictures. The smoothness index of a motion field of each picture is calculated by analyzing the motion vectors for all the macroblocks of a subdivision of the picture, except for the peripheral macroblocks. Spurious detections in the event of noisy pictures, zooming and other situations that may adversely affect either one of the indexes are prevented.

Detection of a change of scene in a motion estimator of a video encoder

The invention relates to a low/very low bitrate video coding method fully compatible with the H.263 standard includes a first forward coding step, a second backwards prediction step, and a third decision step including a selection sub-step between intra and inter coding modes. This decision step controls in the intra coding mode a down-conversion filtering sub-step, carried out at the beginning of the coding step and allowing to code and transmit original intra pictures with a lower resolution, and a corresponding up-conversion filtering sub-step, carried out in the prediction step. In the receiving terminal, the decoder recognizes the reduced format of the pictures and up-scales them.

Video coding method and device, and corresponding decoding device

An algorithm based on a pre-analysis implements an efficient constant bit-rate control with a reduced requirement on a buffer memory capacity. The pre-analysis is on at least one slice (GOS) of the current whole picture, and/or on a mix of information on the pre-analysis of a slice of the preceding picture and on the actual encoding data of the preceding whole picture. The pre-analysis may be carried out by precoding the GOS with a constant reference quantizer or by entropy computation. The local control of the bit-rate is implemented by an integrative-proportional controller.

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Olgiate Molgora, Italy

Daniele Bagni