Abstract: The present invention relates to a method of assembling a first data stream (ds1) with a second data stream (ds2), each data stream comprising coded frames (I,P), each coded frame being associated with a relative time value, specific coded frames of a data stream being preceded by an absolute time value. Said method comprises the steps of: calculating a current reference time value for a current coded frame on the basis of a previous reference time value and on an integer part of the current relative time value, calculating an offset time value on the basis of the reference time value of the last frame in the display order of the first data stream, modifying the absolute time values of the specific coded frames of the second data stream by adding the offset time value to said absolute time values.

Abstract: The invention relates to a method of decoding a video bitstream including base layer and enhancement layer coded video signals, the method comprising the steps of decoding the base layer and enhancement layer coded video signals to produce decoded base layer frames and decoded enhancement layer frames, and displaying the decoded base layer frames either alone or with the decoded enhancement layer frames. According to the invention, each poor quality frame of the base layer to be displayed is replaced by an frame obtained either by means of an interpolation between the two frames of the enhancement layer preceding and following the poor quality frame of the base layer or by only one of these two frames, for example the temporally closest one.

Abstract: In digital mobile broadcast systems, data streams audio and video are sent independently. As this means that both streams may arrive out of sync, they need to be synchronised for reproduction upon reception. For this, the relation between timestamps of both streams should be known. For broadcast, this is difficult because the information is usually not directly available upon the first reception of broadcasted streams and it cannot be send upon playback request. Therefore, the invention proposes to reset counters for generating timestamps upon the start of transmission of the broadcast. The incremental rate of the timestamps can be send on beforehand, as this information usually remains constant over a longer period in time. The invention provides methods for transmission, reception and synchronisation.

Abstract: The present invention relates to a method of determining a corruption indication of a sequence (100) of encoded data frames distributed over a network, said data frames being encoded according to a predictive block-based encoding technique. Said method comprises the steps of: —decoding the sequence of encoded data frames so as to obtain a sequence of decoded data frames (200), —building a reliability map (210) including binary values based on the decoding step, a binary value being associated with a decoded data item in such a way that the binary value is equal to a first value (1) if its associated data item has not been decoded due to corruption or if said associated data item is predicted with reference to a reference data item that has not been decoded due to corruption, and to a second value (0) otherwise, —computing a corruption metric based on the binary values.

Abstract: The present invention relates to a method of determining a corruption indication of a sequence (100) of encoded data frames distributed over a network, said data frames being encoded according to a predictive block-based encoding technique. Said method comprises the steps of: —decoding the sequence of encoded data frames so as to obtain a sequence of decoded data frames (200), —building a reliability map (210) including binary values based on the decoding step, a binary value being associated with a decoded data item in such a way that the binary value is equal to a first value (1) if its associated data item has not been decoded due to corruption or if said associated data item is predicted with reference to a reference data item that has not been decoded due to corruption, and to a second value (0) otherwise, —computing a corruption metric based on the binary values.

Abstract: The present invention relates to a method of assembling a first data stream (ds1) with a second data stream (ds2), each data stream comprising coded frames (I,P), each coded frame being associated with a relative time value, specific coded frames of a data stream being preceded by an absolute time value. Said method comprises the steps of: -calculating a current reference time value for a current coded frame on the basis of a previous reference time value and on an integer part of the current relative time value, -calculating an offset time value on the basis of the reference time value of the last frame in the display order of the first data stream, -modifying the absolute time values of the specific coded frames of the second data stream by adding the offset time value to said absolute time values.

Abstract: Groups of streams of encoded data having different predetermined bit rates are selected for transmission to a client application based on available bandwidth. Common values for at least a part of the decoding parameters are determined so that the decoder can use the same decoding parameter values for decoding stream elements within each group of streams of various bit rates.

Abstract: A data transmission system is formed by a transmitter (50) for processing useful data for the purpose of forming series of information signals, and a receiver (51) for receiving and processing the transmitted series of information signals. In this system, integrity verification is provided for conditionally producing an error indication for the transmitted series of information signals whereby the transmitted series of information signals can be validated even in the case where the error indication appears. Thus, it is possible to transmit image data in a system that has a small bandwidth.

Abstract: The invention relates to a method of streaming multimedia for providing seamless stream switching. The method consists in streaming multimedia data from a server (15) to a client (14) over a network (13) having a variable bandwidth. The client is intended to decode a subset of streams within a set of streams having various predetermined bit rates. The decoded subset of streams has bit rates compatible with the network bandwidth. The method comprises the steps of configuring the client so that the client can decode all the streams within the set of streams, playing all the streams within the set of streams and muting all the streams within the set of streams, except the subset of streams.

Abstract: The present invention relates to a method of resynchronization that attempts to enable a resynchronization of a compressed video data signal received by a decoder, after a transmission error has been detected in said compressed video data signal. The method of resynchronization is based on the use of a resynchronization word. In order to ensure a proper decoding of the compressed video data signal the resynchronization word is distinguishable from the known VLC words as well as the VOP start code.

Abstract: The present invention relates to a method of encoding, which receives an input video signal (IS) for providing a compressed video data signal (CS). Said method comprises the steps of segmentation (SEG) of the input video signal for extracting the video object planes, hereafter referred to as VOP, contained in the video scene; detection (DET) of a non-visible VOP; correction (COR) for converting a bidirectionally predictive coded VOP preceding, in a display order, a non-visible intra or predictive coded VOP that has been detected (Y) by the detection step, into an intra or predictive coded VOP; encoding (ENC) the converted VOP, if a non-visible VOP has been detected by the detection step, or the regular VOP in the opposite case (N), resulting in the compressed video data signal. Use: MPEG-4 encoder.

Abstract: The invention relates to encoding of an input sequence of digital images delivering a base and an enhancement layer bitstream for transmission of video data in real time over a fluctuating-rate transmission channel. The method distributes the encoded data for the images of said sequence between two subsequences of base and an enhancement layer and evaluates degree of occupation of two associated buffers. A notional (virtual, dummy) bi-directional image is created in one of the subsequences which is intended to receive stuffing data, when the degree of occupation on the buffer associated with said subsequences isbelow a predetermined threshold. This method enables the adding of stuffing data in a case not provided for by the MPEG-4 standard, for example, for a sequence encoded in the rectangular mode and having no (regularly coded) bi-directional images (B-frames).

Abstract: The method of streaming multimedia data over a network having a variable bandwidth comprises the steps of encoding data coming from a multimedia source and supplying a set of encoded streams formed with stream elements containing encoded multimedia data. The encoded streams have various predetermined bit rates associated with specific decoding parameter values to be transmitted to a client application decoder for enabling the client decoder to decode the stream elements with respect to their specific decoding parameter values. The encoding step comprises a preliminary step of determining common values for at least a part of the decoding parameters so that the decoder can use the same decoding parameter values for decoding streams elements within at least a group of streams, and a step of building said group of streams, to which common decoding parameter values are assigned.

Abstract: The invention relates to a method and a device for encoding video data consisting of one or several bitstreams according to the MPEG-4 standard. In order to avoid any problem when mapping the video elements into the system elements, a specific alignment/fragmentation mechanism is chosen. According to this mechanism, when said video bitstreams are encoded using the syntax mode corresponding to the fragmentation of the Video Object Planes (VOPs) contained in said video data into Video Packets (VPs)and of Video Packets into Data Partitions (DPs), a Video Data Partition is mapped into one or more SL packets (SL1, SL2, SL3, SL4, . . .), the first Video Data Partition (DP1) start is always mapped to an SL packet start, and the last SL packet transporting the first Data Partition includes the separation marker and up to 7 subsequent bits of the second Data Partition (DP2) in order to obtain byte alignment, the next SL packet starting on the next bit of the second Data Partition.

Abstract: The invention, provided for an implementation, in a video encoder with base layer coding means and enhancement layer coding means, relates to a method of coding the video objects (VOs) of a sequence according to the following steps: segmentation of the sequence, and coding operation of the texture and shape of said VOs. According to a preferred embodiment, the texture coding operation itself comprises motion compensated prediction operations, during which the temporal references of the enhancement layer VO planes (VOPs) of type P or B are selected only on a temporal distance criterion, without any consideration of the layer they belong to.

Abstract: The invention relates to a method and a device for encoding video data consisting of one or several bitstreams according to the MPEG-4 standard. In order to avoid any problem when mapping the video elements into the system elements, a specific alignment/fragmentation mechanism is chosen. According to this mechanism, when said video bitstreams are encoded using the syntax mode corresponding to the fragmentation of the Video Object Planes (VOPs) contained in said video data into Video Packets (VPs) and of Video Packets into Data Partitions (DPs), a Video Data Partition is mapped into one or more SL packets (SL1, SL2, SL3, SL4, . . . ), the first Video Data Partition (DP1) start is always mapped to an SL packet start, and the last SL packet transporting the first Data Partition includes the separation marker and up to 7 subsequent bits of the second Data Partition (DP2) in order to obtain byte alignment, the next SL packet starting on the next bit of the second Data Partition.

Abstract: The invention relates to a method of decoding a video bitstream including base layer and enhancement layer coded video signals, said method comprising the steps of decoding the base layer and enhancement layer coded video signals to produce decoded base layer frames and decoded enhancement layer frames, and displaying the decoded base layer frames either alone or with the decoded enhancement layer frames. According to the invention, each poor quality frame of the base layer to be displayed is replaced by an frame obtained either by means of an interpolation between the two frames of the enhancement layer preceding and following said poor quality frame of the base layer or by only one of these two frames, for example the temporally closest one.

Abstract: The invention, provided for an implementation, in a video encoder with base layer coding means and enhancement layer coding means, relates to a method of coding the video objects (VOs) of a sequence according to the following steps : segmentation of the sequence, and coding operation of the texture and shape of said VOs. According to a preferred embodiment, the texture coding operation itself comprises motion compensated prediction operations, during which the temporal references of the enhancement layer VO planes (VOPs) of type P or B are selected only on a temporal distance criterion, without any consideration of the layer they belong to.

Abstract: This data transmission system is formed by:

Abstract: The present invention relates to a method of resynchronization that attempts to enable a resynchronization of a compressed video data signal received by a decoder, after a transmission error has been detected in said compressed video data signal.