A method for forming a frame sequence, called output sequence (Ss), from an input frame sequence (S E), said input frame sequence having an input spatial resolution (RSε) and an input temporal resolution (RTε), said output sequence having an output temporal resolution (RT S) equal to the input temporal resolution (RT E) and an output spatial resolution (RSs) equal to a predetermined fraction of the input spatial resolution (RSε) by an integer number higher than or equal to 2, characterised in that the method comprises the following steps, implemented for a sub-sequence (SSε) of the input sequence, called current sub-sequence and comprising a predetermined number of frames: - Obtaining a frame rate, associated with said sub-sequence; - Processing the current input sub-sequence, comprising: ∘ temporally sub-sampling the current sub-sequence with a temporal sub-sampling rate comprised between 1 and the predetermined fraction, decreasing with the frame rate obtained, and forming a second sub-sequence having a second temporal resolution (RT 2); ∘ spatially sub-sampling the formed second sub-sequence (SS 2) with a spatial sub-sampling rate comprised between 1 and the predetermined fraction, increasing with the frame rate, so that a product of the temporal and spatial sampling rates is equal to the predetermined fraction and forming a third sub-sequence (SS 3) having a third spatial resolution (RS 3); ∘ when the third spatial resolution (RSs) is higher than the output spatial resolution (RSs), spatially decomposing the frames of the third sub-sequence (SS 3) into at least two sub-frames and at most N sub-frames of spatial resolution equal to the output spatial resolution (RSs) and forming (E2e) the output frame sub-sequence by temporally inserting the sub-frames resulting from the decomposition between the decomposed frame and the following frame; and - inserting the output sub-sequence (SS S) and the associated frame rate into an output container (Cs). - Obtaining a frame rate, associated with said sub-sequence; - Processing the current input sub-sequence, comprising: ∘ temporally sub-sampling the current sub-sequence with a temporal sub-sampling rate comprised between 1 and the predetermined fraction, decreasing with the frame rate obtained, and forming a second sub-sequence having a second temporal resolution (RT 2); ∘ spatially sub-sampling the formed second sub-sequence (SS 2) with a spatial sub-sampling rate comprised between 1 and the predetermined fraction, increasing with the frame rate, so that a product of the temporal and spatial sampling rates is equal to the predetermined fraction and forming a third sub-sequence (SS 3) having a third spatial resolution (RS 3); ∘ when the third spatial resolution (RSs) is higher than the output spatial resolution (RSs), spatially decomposing the frames of the third sub-sequence (SS 3) into at least two sub-frames and at most N sub-frames of spatial resolution equal to the output spatial resolution (RSs) and forming (E2e) the output frame sub-sequence by temporally inserting the sub-frames resulting from the decomposition between the decomposed frame and the following frame; and ∘ temporally sub-sampling the current sub-sequence with a temporal sub-sampling rate comprised between 1 and the predetermined fraction, decreasing with the frame rate obtained, and forming a second sub-sequence having a second temporal resolution (RT 2); ∘ spatially sub-sampling the formed second sub-sequence (SS 2) with a spatial sub-sampling rate comprised between 1 and the predetermined fraction, increasing with the frame rate, so that a product of the temporal and spatial sampling rates is equal to the predetermined fraction and forming a third sub-sequence (SS 3) having a third spatial resolution (RS 3); ∘ when the third spatial resolution (RSs) is higher than the output spatial resolution (RSs), spatially decomposing the frames of the third sub-sequence (SS 3) into at least two sub-frames and at most N sub-frames of spatial resolution equal to the output spatial resolution (RSs) and forming (E2e) the output frame sub-sequence by temporally inserting the sub-frames resulting from the decomposition between the decomposed frame and the following frame; and - inserting the output sub-sequence (SS S) and the associated frame rate into an output container (Cs).