Modifying bitstreams

A modified bitstream which has modification codes in selected parts of the bitstream from which original codes have been removed and appended to an end of the bitstream.

A modified bitstream which has modification codes in selected parts of the bitstream from which original codes have been removed and placed in modification user data portions within the bitstream.

A modified bitstream which has modification codes in selected parts of the bitstream from which original codes have been removed and some placed in modification user data portions within the bitstream and others appended to an end of the bitstream.

Apparatus for modifying a bitstream, the bitstream including digital codes representing information, the apparatus comprising a selecting stage operable to select at least one digital code which occupies a part of the bitstream which is to contain at least one modification code which represents a modification perceptible in the information, a removal stage operable to remove the selected digital code(s) from the said part of the bitstream, a modification code placing stage operable to put the modification code(s) in the said part of the bitstream in place of the selected code(s), wherein the number of bits of the selected code(s) removed from the bitstream is greater than or equal to the number of bits of the said modification code(s) put into the bitstream, and a removed code placing stage operable to (1) store the removed selected code(s) in association with the bitstream and/or (2) place the removed selected codes in one or more removed code data fields in the bitstream.

A data carrier storing a template defining the part or parts of a bitstream which is/are to contain modification code(s) and at least one decryption key.

A method of visibly watermarking a video sequence having intra-encoded pictures and inter-encoded pictures, the pictures comprising data representing blocks of transform coefficients of the video, motion vectors being associated with at least some of the blocks of the inter-encoded pictures, the method comprising

• providing at least one template defining the blocks to be modified to visibly watermark the video,
• modifying at least some transform coefficients in the blocks defined by the template(s) in at least the intra-encoded pictures to visibly watermark the video, and
• setting to zero the motion vectors associated with blocks of the inter-encoded pictures defined by the template(s) and corresponding to the modified blocks of the intra-encoded pictures.

Apparatus for visibly watermarking a video sequence having intra-encoded pictures and inter-encoded pictures, the pictures comprising data representing blocks of transform coefficients of the video, motion vectors being associated with at least some of the blocks of the inter-encoded pictures, the apparatus comprising

• a storage means for storing at least one template defining the blocks to be modified to visibly watermark the video,
• a modifier arranged to modify at least some transform coefficients in the blocks defined by the template(s) in at least the intra-encoded pictures to visibly watermark the video, and
• a means arranged to set to zero the motion vectors associated with blocks of the inter-encoded pictures defined by the template(s) and corresponding to the modified blocks of the intra-encoded pictures.

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