<p>Those are <a href="https://en.m.wikipedia.org/wiki/Compression_artifact" rel="nofollow noreferrer">compression artifacts</a>, where the original video has been compressed and has lost data. Block-based coding for quantisation leads to artifacts like this, as the information depth in the image is too high to be successfully compressed at the level required by the lossy algorithm used. From that Wikipedia page:</p>

<blockquote>
  <p>Lossy data compression involves discarding some of the media's data so that it becomes simplified enough to be stored within the desired disk space or be transmitted (or streamed) within the bandwidth limitations (known as a data rate or bit rate for media that is streamed). If the compressor could not reproduce enough data in the compressed version to reproduce the original, the result is a diminishing of quality, or introduction of artifacts. Alternatively, the compression algorithm may not be intelligent enough to discriminate between distortions of little subjective importance and those objectionable to the viewer.</p>
</blockquote>

<p>@DarkDust worded this well:</p>

<blockquote>
  <p>The part that actually leads to these visible blocks is the fact that for some compression algorithms, each frame is divided into smaller parts, so-called macroblocks, which are further divided into transform blocks. When the compression in two adjacent macro blocks is too far away from the original in different ways, they don't "fit" together at their border any more. It is this "not fitting together" that we see in the block artifacts</p>
</blockquote>

CC BY-SA 3.0
2016-12-12T09:15:42.417Z
2016-12-12T14:16:52.567Z
2016-12-12T14:16:52.567Z
Dr Mayhem
<p><a href="https://i.sstatic.net/yBHCW.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/yBHCW.jpg" alt="enter image description here"></a></p>

<p>This frame from a video about a camera, has, as you can see, a pattern made up from rectangular boxes.<br>
Is it just the pixelation? Or something else?  </p>

<p>*you can see the video by that frame <a href="https://youtu.be/VE0ttSuOh3o?t=206" rel="nofollow noreferrer">here</a></p>

CC BY-SA 3.0
2016-12-12T09:11:34.900Z
This kind of artefact is usually known as "Blocking", and in this case, it's probably cased by YouTube's compression. This paper has more details: http://wavelab.at/papers/Unterweger13a.pdf See also http://forum.videohelp.com/threads/303003-How-to-reduce-blocky-artifacts-in-low-res-low-bitrate-video.
Jonas Czech
<video-quality><non-square-pixels>
What are these rectangular patterns in the frame?
user152435
# What are these rectangular patterns in the frame?

(Asked by: username_0 on 2016-12-12)

[![enter image description here](https://i.sstatic.net/yBHCW.jpg)](https://i.sstatic.net/yBHCW.jpg)

This frame from a video about a camera, has, as you can see, a pattern made up from rectangular boxes.  
Is it just the pixelation? Or something else?

\*you can see the video by that frame [here](https://youtu.be/VE0ttSuOh3o?t=206)

**Tags:** video-quality, non-square-pixels

> **Comments:**
> **username_1**: This kind of artefact is usually known as "Blocking", and in this case, it's probably cased by YouTube's compression. This paper has more details: http://wavelab.at/papers/Unterweger13a.pdf See also http://forum.videohelp.com/threads/303003-How-to-reduce-blocky-artifacts-in-low-res-low-bitrate-video.  

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## 1 answers

### Answer by username_2 on 2016-12-12. Score: 4

Those are [compression artifacts](https://en.m.wikipedia.org/wiki/Compression_artifact), where the original video has been compressed and has lost data. Block-based coding for quantisation leads to artifacts like this, as the information depth in the image is too high to be successfully compressed at the level required by the lossy algorithm used. From that Wikipedia page:

> Lossy data compression involves discarding some of the media's data so that it becomes simplified enough to be stored within the desired disk space or be transmitted (or streamed) within the bandwidth limitations (known as a data rate or bit rate for media that is streamed). If the compressor could not reproduce enough data in the compressed version to reproduce the original, the result is a diminishing of quality, or introduction of artifacts. Alternatively, the compression algorithm may not be intelligent enough to discriminate between distortions of little subjective importance and those objectionable to the viewer.

@DarkDust worded this well:

> The part that actually leads to these visible blocks is the fact that for some compression algorithms, each frame is divided into smaller parts, so-called macroblocks, which are further divided into transform blocks. When the compression in two adjacent macro blocks is too far away from the original in different ways, they don't "fit" together at their border any more. It is this "not fitting together" that we see in the block artifacts


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