Video compression (codecs)

The concept of codec

A non-compressed video image occupies approximately 1 MB. In order to obtain a fluid video, it is necessary to have a frequency of at least 25 or 30 images per second, which produces a data flow of approximately 30 MB/s, that is, more than 1.5 GB per minute. It is obvious that this type of flow is hardly compatible with the storage spaces of personal computers, or even with the network connections of private individuals or small or medium businesses.

Thus, in order to overcome this difficulty, it is possible to resort to algorithms that allow the data flows to be significantly reduced by compressing/decompressing the video data. These algorithms are called CoDec (for COmpression / DECompression).


The first idea which comes to mind after image compression is to apply this type of method to a succession of digital images (animation or video).

The principle of Motion JPEG (written MJPEG or M-JPEG, do not to confuse it with MPEG) consists in successively applying the JPEG compression algorithm to the various images of a video sequence.

Since M-JPEG codes each image of the sequence separately it is possible to randomly access any part of a video. Thus, its flow rate of 8 to 10 Mbps makes it usable in digital assembly studios.

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