Method and device for selecting a transcoding method from a set of transcoding methods

Abstract

The invention relates to a method for selecting a method from a set of methods of transcoding video data, said data being liable to be transmitted between at least two communication apparatuses ( 2, 4 ) via a communication network ( 3 ), wherein said selection method comprises the following steps: determining (S 605 , S 606 S 609 , S 610 ) at least one weighting factor (W 1 , W 2 ) to attribute to each of the transcoding methods of the set, said at least one weighting factor depending on the data to be transcoded, weighting a mean value of at least one characteristic representative of each of the transcoding methods of the set by applying adapted weighting factors (W 1 , W 2 ), selecting a transcoding method as a function of the weighted mean values.

1 . A method for selecting a method from a set of methods of transcoding video data, said data being liable to be transmitted between at least two communication apparatuses via a communication network, wherein said selection method comprises the following steps: 
 determining at least one weighting factor W 1 , W 2  to attribute to each of the transcoding methods of the set, said at least one weighting factor depending on the data to be transcoded,    weighting a mean value of at least one characteristic representative of each of the transcoding methods of the set by applying adapted weighting factors W 1 , W 2 ,    selecting a transcoding method as a function of the weighted mean values.    
   
   
       2 . A selection method according to  claim 1 , wherein it comprises a prior step of classifying the transcoding methods of the set into several types of method, the weighting factor being thus determined according to the type of transcoding method and the weighting step being carried out according to the weighting factor adapted to the type of transcoding method concerned.  
   
   
       3 . A selection method according to  claim 1 , wherein the determination of said at least one weighting factor depends on said at least one characteristic representative of each transcoding method which will be weighted.  
   
   
       4 . A selection method according to  claim 1 , wherein it comprises a prior step of obtaining a mean value of at least one characteristic representative of each of the transcoding methods of the set.  
   
   
       5 - 7 . (canceled)  
   
   
       8 . A selection method according to  claim 1 , wherein a characteristic representative of each of the transcoding methods of the set is a measurement of the quality produced by the method concerned.  
   
   
       9 - 11 . (canceled)  
   
   
       12 . A selection method according  claim 1 , wherein the set of transcoding methods comprises methods of transcoding by reducing the spatial resolution and/or methods of transcoding by re-quantization and/or methods of transcoding by reducing the frame rate.  
   
   
       13 . A method according to  claim 2 , wherein the set of transcoding methods comprises methods of transcoding by reducing the spatial resolution and/or methods of transcoding by re-quantization and/or methods of transcoding by reducing the frame rate and a weighting factor is written as W 1 =1±A′ according to the sign of A′, with A′=|A |/255 2  and A=var−VAR, where var represents a measurement of the variance of the data to be transcoded and VAR represents a measurement of the variance of the training data sequences, the weighting factor W 1  being to be attributed to the methods of transcoding by re-quantization and to the methods of transcoding by reducing the spatial resolution.  
   
   
       14 . A selection method according to  claim 2 , wherein the set of transcoding methods comprises methods of transcoding by reducing the spatial resolution and/or methods of transcoding by re-quantization and/or methods of transcoding by reducing the frame rate and a weighting factor is written as W 2 =1±B′ according to the sign of B′, with B′=|B|/255 2  and B=rmse−RMSE, where rmse represents a measurement of the root mean square error of the data to be transcoded and RMSE represents a measurement of the root mean square error of the training data sequences, the weighting factor W 2  being to be attributed to the methods of transcoding by reducing the frame rate.  
   
   
       15 . A selection method according to  claim 8 , wherein each of the transcoding methods of the set is also represented by at least one of the characteristics which are the format of the images after transcoding by the method concerned, the bit rate produced by the method concerned and the memory space necessary for the decoding of the transcoded data generated by the method concerned.  
   
   
       16 . A selection method according to  claim 1 , wherein it comprises a step of testing the compatibility of each transcoding method with at least one constraint associated with at least one of the communication apparatus and/or with the communication network.  
   
   
       17 . A selection method according to  claim 16 , wherein a constraint corresponds to the authorized rate over the communication network.  
   
   
       18 . A selection method according to  claim 16 , wherein a constraint corresponds to one or more characteristics of one of the communication apparatuses which is intended to receive the digital data.  
   
   
       19 . A device for selecting a method from a set of methods of transcoding video data, said data being liable to be transmitted between at least two communication apparatuses via a communication network, wherein the device comprises: 
 means for determining at least one weighting factor W 1 , W 2  to attribute to each of the transcoding methods of the set, said at least one weighting factor depending on the data to be transcoded,    means for weighting a mean value of at least one characteristic representative of each of the transcoding methods of the set by applying adapted weighting factors W 1 , W 2 ,    means for selecting a transcoding method as a function of the weighted mean values.    
   
   
       20 . A device according to  claim 19 , wherein it comprises means for classifying the transcoding methods of the set into several types of method, the weighting factor being thus determined according to the type of transcoding method and the means for weighting being applied according to the weighting factor adapted to the type of transcoding method concerned.  
   
   
       21 . A device according to  claim 19 , wherein the determination of said at least one weighting factor depends on said at least one characteristic representative of each transcoding method which will be weighted.  
   
   
       22 . A device according to  claim 19 , wherein it comprises means for obtaining a mean value of at least one characteristic representative of each of the transcoding methods of the set.  
   
   
       23 - 25 . (canceled)  
   
   
       26 . A device according to  claim 19 , wherein a characteristic representative of each of the transcoding methods of the set is a measurement of the quality produced by the method concerned.  
   
   
       27 - 29 . (canceled)  
   
   
       30 . A device according to  claim 19 , wherein the set of transcoding methods comprises methods of transcoding by reducing the spatial resolution and/or methods of transcoding by re-quantization and/or methods of transcoding by reducing the frame rate.  
   
   
       31 . A device according to  claim 20 , wherein the set of transcoding methods comprises methods of transcoding by reducing the spatial resolution and/or methods of transcoding by re-quantization and/or methods of transcoding by reducing the frame rate and a weighting factor is written as W 1 =1±A′ according to the sign of A′, with A′=|A|/255 2  and A=var−VAR, where var represents a measurement of the variance of the data to be transcoded and VAR represents a measurement of the variance of the training data sequences, the weighting factor W 1  being to be attributed to the methods of transcoding by re-quantization and to the methods of transcoding by reducing the spatial resolution.  
   
   
       32 . A method according to  claim 20 , wherein the set of transcoding methods comprises methods of transcoding by reducing the spatial resolution and/or methods of transcoding by re-quantization and/or methods of transcoding by reducing the frame rate and a weighting factor is written as W 2 =1±B′ according to the sign of B′, with B′=|B |/255 2  and B=rmse−RMSE, where rmse represents a measurement of the root mean square error of the data to be transcoded and RMSE represents a measurement of the root mean square error of the training data sequences, the weighting factor W 2  being to be attributed to the methods of transcoding by reducing the frame rate.  
   
   
       33 . A device according to  claim 26 , wherein each of the transcoding methods of the set is also represented by at least one of the characteristics which are the format of the images after transcoding by the method concerned, the bit rate produced by the method concerned and the memory space necessary for the decoding of the transcoded data generated by the method concerned.  
   
   
       34 . A device according to  claim 19 , wherein it comprises means for testing the compatibility of each transcoding method with at least one constraint associated with at least one of the communication apparatuses and/or with the communication network.  
   
   
       35 . A device according to  claim 34 , wherein a constraint corresponds to the authorized bit rate over the communication network.  
   
   
       36 . A device according to  claim 34 , wherein a constraint corresponds to one or more characteristics of one of the communication apparatuses which is intended to receive the digital data.  
   
   
       37 . A communication apparatus, wherein it comprises a device for selecting a method from a set of methods of transcoding video data according to  claim 19 .  
   
   
       38 . An information storage means which can be read by a computer or a microprocessor containing code instructions of a computer program for executing the steps of the method of selecting a method from a set of methods of transcoding video data according to  claim 1 .  
   
   
       39 . An information storage means which is removable, partially or totally, which can be read by a computer or a microprocessor containing code instructions of a computer program for executing the steps of the method of selecting a method from a set of methods of transcoding video data according to  claim 1 .  
   
   
       40 . A computer program which can be loaded into a programmable apparatus, wherein it contains sequences of instructions or portions of software code for implementing the steps of the method of selecting a method from a set of methods of transcoding video data according to  claim 1 , when this computer program is loaded and executed by the programmable apparatus.