The main standards used presently, notably MPEG4/H264, for the compression of video streams, provide the allocation of a certain throughput to the compressed stream, measured in bits per second, independently of the number of images per second contained in the original stream. Thus, a video file of 10 seconds encoded with a compression throughput of 10 megabits per second (10 Mbps) will have a size of 100 megabits (100 Mb), i.e. 12.5 megabytes (12.5 Mbytes), whether its display frequency is of 50 images per second, i.e. the file contains 500 images or whether its display frequency is 25 images per second, i.e. the file contains 250 images. Further, the codec applying the H264 standard generates in the stream or in the compressed file obtained from the stream or from the original file, groups of images (Group Of Pictures (GOP)). Each group comprises 3 types of compressed images:                a reference image said to be of type I, slightly compressed;        one or more more compressed images P, predicted and restored only depending on the preceding images of the GOP,        one or more images B predicted and restored both from the preceding and following images of the GOP.        
The quality of the restored stream depends on the selected throughput and on the frequency of display and restoration of the processed stream, both of these frequencies being identical with each other in the case of the H264 standard, which retains the number of images between the original stream and the compressed stream. The compression throughput may be selected at the moment of the compression; a throughput of 10 Mbps will allow a restoration of better quality than a throughput of 5 Mbps.
The quality of the restored stream is also dependent on how the GOP is obtained, and therefore on the structure of each GOP, notably on the quality of the reference image of type I, on the number of images of each type B or P like on their ordering. A large number of P images may thus give a jerky aspect during restoration. A large number of images of type B or P between two successive reference images of type I, may cause gradual degradation of the restored video, between both reference images, therefore a video of lesser quality.
The H264 standard is widely used for compressing Internet and television video streams. However, restorations of compressed streams, notably according to the standard, have defects which are visibly apparent for the television viewer, while the latter is increasingly more demanding as to the quality of the restoration.