Method of coding a video image stream with a view for subsequent recoding using the same type of code

Method of recoding a video image stream arising in the form of a video image coded stream comprising a coding signature representing first encoding constraints and coding parameters allowing the reconstruction of the video image stream, said coding signature being identified in said coded stream as a data item to be retained with a view to a subsequent recording,

• in which the recoding is carried out with the aid of a compression code of the same type as the code used previously, the code being an image compression code with information loss which uses coding parameters, and in which parameters of the previous coding are transmitted with the image stream;
• comprising the steps of:
• decoding said video image coded stream into a decoded signal, using a video decoder;
• including in the decoded signal some of the coding parameters which are used during the previous coding with a view to a subsequent reuse of said parameters;
• incorporating, during decoding step, the coding signature into the decoded signal among the some of the coding parameters;
• verifying the coding signatures associated with the images of the said stream so as to validate or to invalidate all or some of the parameters according to the said signatures;
• and
• recoding said video image stream, using a video encoder.

Method of recoding a video image stream previously coded according to the steps of:

• encoding said video image stream into a coded stream so as to respect first encoding constraints, using a video encoder;
• inserting into said coded stream coding parameters allowing the reconstruction of the video image stream,
• introducing a coding signature into the coded stream, said signature representing said first encoding constraints, and
• identifying said signature as a data item to be retained with a view to a subsequent recoding;
• and further decoded according to the steps of:
• decoding said video image coded stream into a decoded signal, using a video decoder;
• including in the decoded signal some of the coding parameters which are used during the previous coding with a view to a subsequent reuse of said parameters;
• incorporating, during decoding step, the coding signature into the decoded signal among the some of the coding parameters;
• in which the recoding is carried out with the aid of a compression code of the same type as the code used previously, the code being an image compression code with information loss which uses coding parameters, and in which parameters of the previous coding are transmitted with the image stream, comprising the steps of:
• verifying the coding signatures associated with the images of the said stream so as to validate of to invalidate all or some of the parameters according to the said signatures;
• and
• recoding said video image stream, using a video encoder.

Method of decoding a video image stream with a view to a subsequent recoding using a same type of code, the code being an image compression code with information loss which uses coding parameters, said video stream being previously coded according to the steps of:

• encoding said video image stream into a coded stream so as to respect first encoding constraints, using a video encoder;
• inserting into said coded stream coding parameters allowing the reconstruction of the video image stream,
• introducing a coding signature into the coded stream, said signature representing said first encoding constraints, and
• identifying said signature as a data item to be retained with a view to a subsequent recoding;
• said method of decoding comprising the steps of:
• decoding said video image coded stream into a decoded signal, using a video decoder;
• including in the decoded signal some of the coding parameters which are used during the previous coding with a view to a subsequent reuse of said parameters;
• incorporating, during decoding step, the coding signature into the decoded signal among the some of the coding parameters,
• wherein the method of decoding further comprises the steps of:
• associating, during decoding step, at least one decoding signature representative of at least one zone of each decoded image of the stream, said decoding signature being a word of n bits corresponding to a modular reduction of the sum of all the bits of the luminance and chrominance levels of the image zone;
• and
• placing this signature in the decoded signal with the coding parameter.