101 – Compression

101 – Compression
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Lets talk compressing types


Loss·y Compression

lossy compression or
irreversible compression is the class of data encoding methods that uses inexact approximations and partial data discarding to represent the content. These techniques are used to reduce data size but will also degrade the image as the original pixel data is gone

Original

50%

25%


Loss·less Compression

Lossless compression is a method of data compression in which the size of the file is reduced without sacrificing image quality. Unlike lossy compression, no data is lost when this method is used. Because the data is preserved, the technique will decompress the data and restore it exactly to its original state.

Original

Can be uncompressed

without data loss

RLE Compression

Compressed down to 17%

Run-length encoding (RLE) is a very simple form of lossless data compression in which runs of data are stored as a single data value and count, rather than as the original run.
This is most useful on data that contains many such runs. Consider, for example, simple graphic images such as icons, line drawings, and mostly black pixels. It is not useful with files that don't have many runs as it could greatly increase the file size.


Compression Examples

When should you compress?

Any media being introduced into the workflow should always be data checked and if needed re-saved into a lossless format. Formats which contain proprietary formats ( PSD, Tiff, etc. ) should have a Master and production version.

CONVERT TO LOSSLESS ► ► ►

► ► ► ALWAYS LOSSLESS ► ► ►

NORMALLY LOSSY ► ► ►

LOSSY EXPORT

If your client is just viewing images then lossy is ok. This allows them to view it on websites and most computers quickly.

LOSSLESS EXPORT

Client should always receive a master version that is not lossy.
Lossless will allow compressing while not losing any data.

Basic Video Compression

Chroma sub-sampling

a : b : c
a = Pixels across are sampled (YUV)
b = Pixels across have there own chroma (U+V)
c = In row 2 that have there own chroma (U+V)

4:4:4
No compression and transports both luminescence and color data entirely

4:2:2
Half the sampling rate horizontally, but will maintain full sampling vertically.

4:2:0
Sample colors out of half the pixels on the first row and ignores the second row of the sample completely.

Mike Oakely

Mike Oakely

Mike Oakley is a seasoned and passionate freelance visual effects artist in Seattle, Wa. He is a true generalist. Animations, material creations, FX, composting, editing, audio are all skills he enjoys working with. In 2013 he won a Emmy for Outstanding Special Visual Effects in a Supporting Role for the episodic "Banshee". His energetic attitude, strong work ethic and creative insight assures projects are completed on time and exceed expectations. He enjoys changing of hats on a project to fill in gaps on a production.