'General'

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"Resolution and Compression" by Ashish Rastogi


Hello everybody, on request of various 3dtotal.com visitors I am writing this tutorial. Resolution, Rendering, Compression makes the animators, digital filmmaker's life hell that traditional filmmakers do not have to deal with. So, let's talk about it.


Resolution

Television sets in the US use a resolution of 525 scan lines, which is called the NTSC standard (National Television System Committee). Most European Countries follow the PAL standard which is 625 scan lines.

NTSC- The standards setting body for television and video in the United States. It is the sponsor of the standard for encoding color, a coding system compatible with black-and-white signals and the system used for color broadcasting in the United States.

Take an example, when u increases the size of the image in Photoshop 800% or more. The picture is fairly crude and cannot portray the details of the scene. Given that, when smaller tiles are used, pictures become smoother and details become more visible. The number of tiles used in the height and width of the picture is what constitutes its resolution.

In my previous tutorial "72 DPI or 300 DPI" I already explain in printing its referred to as DPI and on video screens as pixels. To increase the resolution you have to increase the number of pixels a picture contains. Once a picture is produced you cannot increase the resolution but you can convert it into lower resolution. One thing I would like to mention Computer screen uses square pixels but television uses rectangular pixels.

Many newcomers to computer graphics are frustrated when they first confront this problem because not much information about it is readily available. Following table can help.

Format
Resolution
Frame per second
NTSC
720 x 480
29.97fps
PAL
720 x 576
25.00fps

 

Compression

Compressed files are smaller; they download faster and require less space for storage. The more compression you have, the less or say poor quality you will end up with. Uncompressed video has a compression ratio of 1:1, while compressed video can range anywhere from 10:1 to 1.6:1. Video compressed at a 10:1 ratio has 10% of its original data.

Most compression algorithms work by reducing unnecessary, redundant color information in each frame. Most of the information that your eye perceives is light versus dark, or luminance. In fact, your eye is not very good at perceiving color information, or chrominance. Because your camera can capture more color than your eye can perceive, compression software can afford to throw out the colors that your eye is less sensitive to, resulting in less color data and, therefore, smaller files Video is compressed using a piece of software called a codec, or Compressor/ Decompressor.

 

CODECs are usually managed by the video architecture-QuickTime, Video for Windows, Real Media, and so forth-that you are using. If you have ever created a QuickTime movie on your computer, you have probably been presented with a choice of the different compression options that QuickTime provides. Video, Sorenson, Animation, Cinepak, and many others are all CODECs that are used to compress video for storage, and then to decompress it for playback. Different CODECs are used for different purposes. You'll use high-compression/ low-quality CODECs for Web or CD-ROM delivery, and low-compression/high-quality CODECs for higher-quality playback. Other CODECs are used if you are using special video hardware. CODECs can be either lossy or lossless; that is, they either degrade the image quality, or leave it unaffected.

 

Output
Format to render
Codec
Resolution
Video
Tga, rla, rpf, iff, tif
(always render in image sequences so you can composite with reduction in quality )
No compression
According, for which type of video you are rendering. PAL, NTSC, IMAX etc.
Web/CD
Quicktime (cross platform), Avi
Divx (preferred) , Xvid, cinepak
You have to decide which aspect ratio you want 4:3, 16:9.
Print
Tiff
No compression
300 DPI


As you know suggestions and comments are always welcome on my email.

Byeeeeeeeeeee.

 

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