Problems related to video coding

High rate of compression

High rates of compression will result in the block structure of the image being visible or to excessive noise within the image.  This will generally persist throughout a video sequence at a fairly constant level.

Example of pixellation due to a compression problem

Transcoding errors

Transcoding errors can lead to blocks of mis-colored pixels appearing within the image.  These could be due to read errors from disk drives or magnetic tape, or to transmission errors between the video source and the transcoding system.

Pixellation

The term "Pixellation" (or Pixelation) is sometimes used to refer to the colored blocks of pixels that arise from transcoding errors, or from errors during the encoding process, and sometimes to the coarse rectangular structure that would typically result either from a very high rate of compression or high rates of motion within the video sequence.

Edge noise

Noise around sharp edges in the image may be edge noise or mosquito noise.  This is typically due to the compression level being too high.

Quantization noise

Quantization noise will appear as overall degradation of the image and is due to the use of coarse quantization within the encoding process.

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