Method for forming an output image sequence from an input image sequence, method for reconstructing an input image sequence from an output image sequence, associated devices, server equipment, client equipment and computer programs

A method for reconstructing a frame sequence that is a current input sequence having an input spatial resolution and an input temporal resolution, from an output container including an output sequence having an output spatial resolution equal to 1/N times the input spatial resolution with an integer N higher than or equal to 2, and an output temporal resolution equal to the input temporal resolution, said frame sequence being temporally cut into a plurality of sub-sequences, said method, implemented for a first current sub-sequence of the output sequence that is a current output sub-sequence and including a predetermined number of frames, comprising:

• obtaining the current output sub-sequence of the output sequence from the output container and obtaining information representative of a frame rate associated with said current output sub-sequence;
• and
• processing the current output sub-sequence by:
• when the current output sub-sequence has the associated frame rate that is lower than the output temporal resolution, spatially recomposing at least two successive frames of the current output sub-sequence into a frame of second spatial resolution higher than the output spatial resolution and lower than or equal to the input spatial resolution to form a second current sub-sequence of second temporal resolution equal to the frame rate,
• when the second spatial resolution is lower than the input spatial resolution, spatially over-sampling frames of the second current sub-sequence with a spatial over-sampling rate comprised between 1 and the integer number N, which increases with the frame rate, to obtain a third current sub-sequence of spatial resolution equal to the input spatial resolution, and
• when the second temporal resolution of the third current sub-sequence is lower than the input temporal resolution, reconstructing a current input sub-sequence by temporal recopy of at least one frame of the third current sub-sequence between two successive frames of the third current sub-sequence to obtain a reconstructed sub-sequence of the frame sequence having the input temporal resolution.

A device for forming a frame sequence that is an output sequence, from an input frame sequence having an input spatial resolution and an input temporal resolution, said output sub-sequence having an output temporal resolution equal to the input temporal resolution and an output spatial resolution equal to a predetermined fraction 1/N of the input spatial resolution by an integer number N higher than or equal to 2, the device comprising:

• at least one processor configured to, for a first sub-sequence of the input frame sequence that is a current input sub-sequence and including a predetermined number of frames:
• obtain the current input sub-sequence and a frame rate, associated with said current input sub-sequence,
• process the current input sub-sequence, by:
• temporally sub-sampling the current input sub-sequence with a temporal sub-sampling rate comprised between 1 and the predetermined fraction 1/N, decreasing with the frame rate, and obtaining a second sub-sequence having a second temporal resolution,
• spatially sub-sampling the second sub-sequence with a temporal sub-sampling rate comprised between 1 and the predetermined fraction 1/N, increasing with the frame rate, so that a product of the temporal sampling rate and the spatial sampling rate is equal to the predetermined fraction 1/N, and obtaining a third sub-sequence having a third spatial resolution, and
• when the third spatial resolution is higher than the output spatial resolution, spatially decomposing frames of the third sub-sequence into at least two sub-frames of spatial resolution equal to the output spatial resolution, and forming an output frame sub-sequence of the output sequence by temporally inserting the decomposed at least two sub-frames between the respective decomposed frame and a following frame, and
• inserting the output frame sub-sequence and the associated frame rate in an output container.

A device for reconstructing a frame sequence that is a current input sequence, having an input spatial resolution and an input temporal resolution, from an output container including an output sequence having an output spatial resolution equal to 1/N times the input spatial resolution with an integer N higher than or equal to 2 and an output temporal resolution equal to the input temporal resolution, said frame sequence being temporally cut into a plurality of sub-sequences, said device comprising

• one or more processors configured to:
• obtain a first current sub-sequence of the output sequence from an output container and obtain information representative of a frame rate associated with said first current sub-sequence that is a current output sub-sequence, and
• process the current output sub-sequence by:
• when the current output sub-sequence has the associated frame rate that is lower than the output temporal resolution, spatially recomposing at least two successive frames of the current output sub-sequence into a frame of second spatial resolution higher than the output spatial resolution and lower than or equal to the input spatial resolution to form a second current sub-sequence of second temporal resolution equal to the frame rate,
• when the second spatial resolution is lower than the input spatial resolution, spatially over-sampling frames of the second sub-sequence with a spatial over-sampling rate comprised between 1 and the integer number N, which increases with the frame rate, to obtain a third current sub-sequence of spatial resolution equal to the input spatial resolution, and
• when the second temporal resolution of the third current sub-sequence is lower than the input temporal resolution, reconstructing a current input sub-sequence of the current input sequence by temporal recopy of at least one frame of the third current sub-sequence between two successive frames of the third current sub-sequence to obtain a reconstructed sub-sequence of the frame sequence having the input temporal resolution.