Prototyping 2013-11-05 (Lens Based Media): Difference between revisions
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== Encoding/Compressing == | == Encoding/Compressing == | ||
Why do we compress? | '''Why do we compress?''' | ||
* Image- and videofile sizes reduced | * Image- and videofile sizes reduced | ||
* More files to store, or longer videos | * More files to store, or longer videos | ||
| Line 22: | Line 22: | ||
* Downside: someone has to decode! | * Downside: someone has to decode! | ||
[[File:jpegcompression.png|thumb|right|400px|jpeg compression]] | [[File:jpegcompression.png|thumb|right|400px|jpeg compression]] | ||
<br /> | |||
Types of compression | ===Types of compression'=== | ||
* '''Intraframe''' compression | * '''Intraframe''' compression | ||
** Compresses each frame (so similar to image compression, with for instance JPG) | ** Compresses each frame (so similar to image compression, with for instance JPG) | ||
| Line 31: | Line 32: | ||
** Apple ProRes, DNxHD (Avid) | ** Apple ProRes, DNxHD (Avid) | ||
* '''Interframe''' Compression | * '''Interframe''' Compression | ||
** Compress BETWEEN frames | ** Compress BETWEEN frames | ||
** effective size compression | ** effective size compression | ||
| Line 41: | Line 42: | ||
=== encoding techniques === | === encoding techniques === | ||
* Run length encoding > Looks for identical segments (often lossless) | * Run length encoding > Looks for identical segments (often lossless) | ||
* Transform coding > Most used (jpeg, DCT, wavelet) (selectively removes ‘non-relevant’ detail from the image). | * [http://www.popmodernism.org/appropirate/delta.html| Transform coding] > Most used (jpeg, DCT, wavelet) (selectively removes ‘non-relevant’ detail from the image). | ||
* [http://www.knotless.com/1/post/2012/07/the-mysteries-of-chroma-sub-sampling.html| Chroma subsampling] >Selective loss of resolution (4:4:4 vs 4:2:0) | * [http://www.knotless.com/1/post/2012/07/the-mysteries-of-chroma-sub-sampling.html| Chroma subsampling] >Selective loss of resolution (4:4:4 vs 4:2:0) | ||
* Reducing bit-depth (reducing colour accuracy) | * Reducing bit-depth (reducing colour accuracy) | ||
Revision as of 22:04, 4 November 2013
Compression & Codecs in video
(File)Format or Container is the shipping box, codec is the goods inside the box.
Format
- determines the way audio and video streams (and other metadata) are stored inside the file
- Examples are :
- .avi (Microsoft -> OLD)
- .wmf (Microsoft -> Unflexible)
- .mov (Apple -> supports a lot of codecs)
- .ogg (Open Source -> but not very well supported by editing software)
- .mkv (Open Source -> but not very well supported by editing software)
- .mp4 (works on virtually all platforms)
Encoding/Compressing
Why do we compress?
- Image- and videofile sizes reduced
- More files to store, or longer videos
- Faster to download
- Downside: someone has to decode!
Types of compression'
- Intraframe compression
- Compresses each frame (so similar to image compression, with for instance JPG)
- No effective size compression
- High Quality
- Easily readable by edit software
- Apple ProRes, DNxHD (Avid)
- Interframe Compression
- Compress BETWEEN frames
- effective size compression
- Not easy for edit software
- Use for sharing -> final output
- MPEG-2 (DVD's, hardware players), DivX (downloads), H264 (currently has best quality vs. file ratio)
encoding techniques
- Run length encoding > Looks for identical segments (often lossless)
- Transform coding > Most used (jpeg, DCT, wavelet) (selectively removes ‘non-relevant’ detail from the image).
- Chroma subsampling >Selective loss of resolution (4:4:4 vs 4:2:0)
- Reducing bit-depth (reducing colour accuracy)
- Fractal compression (replacing pixels with mathematic approximations)
FYI: Uncompressed HD video = 400GB per hour
More Info
[1]
Encoding Tools
- ffmpeg (ffmpegX for a Mac gui version)
- Mencoder
- Handbrake
- Mpegstreamclip
- Adobe Media Encoder
Bitrate + Framesize
Workflow, Archiving & Delivery
There's no solution to the question 'What is the best setting for my video?". All depends on the platform you will deliver to!
- How do you record?
- How do you edit?
- What do you deliver?
Glitch Art & Data moshing
{{#ev:youtube|mvqakws0CeU?version=3&autohide=1&showinfo=0}}