Abstract: An MPEG video stream generator, which contains several slightly different programs, each with approximately the same content. The MPEG stream is constructed in such a manner that a simple transcoder can effectively select one of the programs. This is achieved by storing the differences relative to the default program in selected user data fields. The transcoder is little more than an MPEG bitstream parser, which replaces the bits corresponding to selected set of macroblocks by the replacement data stored in the user data fields. A standard MPEG decoder without any knowledge of the embedded user data fields will simply extracted the default program. One application relates to broadcasting of a television program with or without a logo, or a commercial with or without a public warning. Another application relates to copy-protection schemes. In such a scheme, the default program contains a ticket indicating that the contents may be copied once.

Abstract: By coding (ENC1) data (D), coded data (CD) and, in addition, a set of parameters (PAR) for decoding (DEC1) the coded data (CD) are obtained. MPEG video coding is an example of such a coding. The coded data (CD) is modified by carrying out the following steps. The coded data (CD) is, at least partially, decoded (DEC1) so as to obtain decoded data (DD). The decoded data (DD) is modified (MOD) so as to obtain modified data (MD). The modified data (MD) is coded (ENC) so as to obtain coded modified data (CMD). It is examined (EXAM) whether a satisfactory result will be obtained if the set of parameters (PAR) for decoding the coded data (CD) is applied for decoding (DEC2) the coded modified data (CMD). If the result is satisfactory, the set of parameters (PAR) for decoding the coded data (CD) is added to the coded modified data (CMD). If the result is not satisfactory, a new set of parameters (PAR) is established (ADP) and the new set of parameters (APAR) is added to the coded modified data (CMD).

Abstract: Data (D) is compressed in dependence on a compression parameter (CPAR). An example of such data compression is coding a sequence of pictures in accordance with a standard defined by the Moving Pictures Experts Group. In the process of compressing the data (D), the following three steps are repetitively carried out. In a prediction step (PRD), it is predicted, on the basis of an initial value (VALint) of the compression parameter (CPAR), which amount of compressed data Xprd will have been obtained at a future instant of time (Tfut). In an adaptation step (ADP), the initial value (VALint) is adapted on the basis of a difference (&Dgr;X) between the predicted amount of data (Xprd) and a desired amount of data (Xdes), so as to obtain an adapted value (VALadp) of the compression parameter (CPAR). In an application step (APL), the adapted value (VALadp) of the compression parameter (CPAR) is applied until a subsequent prediction step (PRD) followed by a subsequent adaptation step (ADP) is carried out.

Abstract: The bit rate of a data stream having the following characteristics is modified. The data stream includes control words, each of which defines when a data portion of the data stream has to be read from an input buffer at a receiving end. An MPEG video stream has such characteristics. It is calculated, for at least one future instant in time (Tfut), within which bounds (Rmax, Rmin) the bit rate (R) of the data stream can be modified at that future instant of time, so as to cause neither underflow nor overflow of the input buffer. The bit rate is modified at a future instant in time within the bounds (Rmax, Rmin) which have been calculated for the future instant in time. This allows a fast modification of the bit rate which generally contributes to the quality of the data comprised in the data stream.

Abstract: A data compression assembly has several data-compression channels (DCC). The data-compression channels may be, for example, encoders which encode different programs in accordance with an MPEG standard. A data-compression channel comprises a data compressor (CMP) and a buffer-memory space (BUF). The data compressor compresses input data (D) so as to obtain compressed data (Dc). The buffer-memory space temporarily stores the compressed data and provides the compressed data in the form of an output data stream (DS). Indications (IND) of compressed-data quality (Q[Dc]) versus extent of compression (E[CMP]) are established for respective data-compression channels. A total output bit rate (Rtot) is partitioned over respective output data streams in dependence on these indications. The extent of compression in respective data-compression channels is controlled individually on the basis of output data stream bit rate (R) and amount of compressed data (F) stored in the buffer memory space.

Abstract: Data (D) is compressed in dependence on a compression parameter (CPAR). An example of such data compression is coding a sequence of pictures in accordance with a standard defined by the Moving Pictures Experts Group. In the process of compressing the data (D), the following three steps are repetitively carried out. In a prediction step (PRD), it is predicted, on the basis of an initial value (VALint) of the compression parameter (CPAR), which amount of compressed data Xprd will have been obtained at a future instant of time (Tfut). In an adaptation step (ADP), the initial value (VALint) is adapted on the basis of a difference (&Dgr;X) between the predicted amount of data (Xprd) and a desired amount of data (Xdes), so as to obtain an adapted value (VALadp) of the compression parameter (CPAR). In an application step (APL), the adapted value (VALadp) of the compression parameter (CPAR) is applied until a subsequent prediction step (PRD) followed by a subsequent adaptation step (ADP) is carried out.

Abstract: A basic transcoder, that decodes an encoded data stream and re-encodes it, may be used for locally modifying data in said stream. Said modification is carried out by defining a predicted data stream on the basis of a given modifying data stream and adding to the decoded stream—between the decoding and re-encoding parts of the transcoder—the difference between the modifying data stream and the predicted one. In an improved implementation, the modifying data stream is preprocessed so that it may be obtained in the decoded data stream a local substitution of said modifying data to the decoded ones.

Abstract: A data stream (DS) comprises a time multiplex of coded data (D) and control data (C). The data stream (DS) may be, for example, of the MPEG type representing a sequence of pictures. The coded data (D) is transcoded (T) so as to obtain transcoded data (DT) which differs in size from the coded data (D). The control data (C) is adapted for the transcoded data (DT) so as to obtain adapted control data (CA) which does not substantially differ in size from the control data (C). The transcoded data (DT) and the adapted control data (CA) are written into a transcoder output buffer (TOB) and read from the transcoder output buffer (TOB) so as to obtain a transcoded data stream (DST). This allows an efficient use of a transmission channel via which the transcoded data stream (DST) is to be transmitted and, consequently, it allows a satisfactory transcoding quality.

Abstract: Data (D), which has been coded by a coder (COD) so as to obtain coded data (CD), is modified. The data (D) may be, for example, a sequence of pictures which has been coded in accordance with an MPEG standard. The data (D), which is available in a coded form, is modified in the following manner. A partial decoder (PDEC) partially decodes the coded data (CD). That is, of a series of decoding steps (Sd(1) . . . Sd(N)) which need to be carried out in order to decode the coded data (CD), the partial decoder (PDEC) carries out only a first few decoding steps (Sd(1) . . . Sd(K)), with K and N being integers and K being smaller than N. Accordingly, partially decoded data (PDD) is obtained. A data-modifier (MOD) modifies the partially decoded data (PDD). Accordingly, modified partially decoded data (MPDD) is obtained. A complementary coder (CCOD) complementary codes the modified partially decoded data (MPDD). That is, the complementary coder (CCOD) carries out one or more coding steps (Sc(K) . . .

Abstract: A data stream (DS) comprises a time multiplex of coded data (D) and control data (C). The data stream (DS) may be, for example, of the MPEG type representing a sequence of pictures. The coded data (D) is transcoded (T) so as to obtain transcoded data (DT) which differs in size from the coded data (D). The control data (C) is adapted for the transcoded data (DT) so as to obtain adapted control data (CA) which does not substantially differ in size from the control data (C). The transcoded data (DT) and the adapted control data (CA) are written into a transcoder output buffer (TOB) and read from the transcoder output buffer (TOB) so as to obtain a transcoded data stream (DST). This allows an efficient use of a transmission channel via which the transcoded data stream (DST) is to be transmitted and, consequently, it allows a satisfactory transcoding quality.

Abstract: A data stream (DS) comprises a time multiplex of coded data (D) and control data (C). The data stream (DS) may be, for example, of the MPEG type representing a sequence of pictures. The coded data (D) is transcoded (T) so as to obtain transcoded data (DT) which differs in size from the coded data (D). The control data (C) is adapted for the transcoded data (DT) so as to obtain adapted control data (CA) which does not substantially differ in size from the control data (C). The transcoded data (DT) and the adapted control data (CA) are written into a transcoder output buffer (TOB) and read from the transcoder output buffer (TOB) so as to obtain a transcoded data stream (DST). This allows an efficient use of a transmission channel via which the transcoded data stream (DST) is to be transmitted and, consequently, it allows a satisfactory transcoding quality.

Abstract: A data stream (DS) comprises a time multiplex of coded data (D) and control data (C). The data stream (DS) may be, for example, of the MPEG type representing a sequence of pictures. The coded data (D) is transcoded (T) so as to obtain transcoded data (DT) which differs in size from the coded data (D). The control data (C) is adapted for the transcoded data (DT) so as to obtain adapted control data (CA) which does not substantially differ in size from the control data (C). The transcoded data (DT) and the adapted control data (CA) are written into a transcoder output buffer (TOB) and read from the transcoder output buffer (TOB) so as to obtain a transcoded data stream (DST). This allows an efficient use of a transmission channel via which the transcoded data stream (DST) is to be transmitted and, consequently, it allows a satisfactory transcoding quality.

Abstract: A basic transcoder, that decodes an encoded data stream and re-encodes it, may be used for locally modifying data in said stream. Said modification is carried out by defining a predicted data stream on the basis of a given modifying data stream and adding to the decoded stream—between the decoding and re—encoding parts of the transcoder—the difference between the modifying data stream and the predicted one. In an improved implementation, the modifying data stream is preprocessed so that it may be obtained in the decoded data stream a local substitution of said modifying data to the decoded ones.