Tech report
- 1. Tech Report Framerate, Video Format, Screen Ratio, Resolution, and compression
- 2. Frame Rate The framerate of a video is the amount of frames (individual still images) in each second of movement, and is consequently measured in fps (frames per second). There are many different framerates used in film, television and cinema, and all have their own advantages and disadvantages though any framerate above roughly15 fps will be recognised as movement , not still images, by the brain. 24fps – The original framerate of 35mm film cameras and optical projectors, and also the standard framerate of hand-drawn animation. Produces fluid movement with very little noticeable judder. 25fps – Similar results and quality to 24fps, but worth mentioning as it is the standard framerate for PAL television. 30fps – Used similarly to 24fps in film, but with less noticable judder. 50/60fps – Produces negligible judder, mostly found in HD formats. 1000-10,000fps – The standard for slow motion. The higher the framerate, the more frames in the film, therefore playing back at lower framerates produces slower video. 1,000,000,000,000 fps – A trillion frames per second. Never used for commercial applications, but recently achieved by scientists at MIT to study the movement of light.
- 3. Video Format Format refers to the way that digital video is stored and interpreted by a computer. Different formats accomplish different tasks better and can be interpreted and manipulated more easily on different systems. Formats are distinguished by a file extension such .gif or .mkv. Some common video and audio formats include: .mp3 - The standard format for audio, widely recognised by nearly all systems and software. .mp4 – The standard video format for the internet: is recognised by Youtube, Flash and HTML5. .avi – A format developed by Microsoft that runs on all Windows sofware and is common online. .mov/Quicktime – Similar to .avi, but developed my Apple for the Mac system. .swf/.flv/Flash – Built for the internet by Macromedia and subsequently taken over by Adobe. Has wide support on almost all platforms.
- 4. Screen Ratio The screen ratio of a film or video refers to the width and height of the moving image, and their relation to one another. Different screen or aspect ratios will result in differently sized and shaped images. Much like framerate and format, there are a variety of different aspect ratios with different uses, advantages and disadvantages. The two standard and most common commercial aspect ratios used are 4:3 and 16:9. Scaled for clarity Some other less common aspect ratios include: 3:2 – The aspect ratio of 35mm film, usually the standard film stock for feature production. 2.39:1/2.40:1 – The aspect ratio found in widescreen cinema. Cinema 35mm Film Widescreen
- 5. Resolution Similar in some ways to aspect ratio, the resolution of a video describes its size: the higher the resolution the more pixels in the image, and the higher the pixel count, the better the quality of the image. Some common resolutions include: 480i – Standard for NTSC standard-definition television (North America) 576i – Standard for PAL standard-definition television (Europe and GB) 720p - 1280 x 720 pixels , standard resolution for high definition video in many different formats. Aspect ratio is 16:9. 1080p- 1920 x 1080 pixels, standard resolution for high definition video in many different formats. Aspect ratio is also 16:9. A chart showing many different resolutions and their relevant sizes.
- 6. Compression Compression refers to the act of eliminating large chunks of data from a video or image to decrease its digital ‘size’ while still retaining as much visual information as possible to reserve quality. Typically video is compressed by comparing groups of pixels(grouped my colour, size and shape) from frame to frame retaining the information only of those areas that change from one frame to the next. In moments of very little change, action or movement the effect of eliminating this information is negligible, though may lead to disfiguring artefacts on the image. However, the effects of compression become most notable in scenes where there is a lot of change between frames, such as in a high-action sequence involving fast camera movements, flames or explosions. At this point the quality of the image degrades very quickly and causes the image to contain very noticeable artefacts and aberrant pixels. Three images exhibiting the effects of compression on a .jpg image that relies on lossy compression to reduce filesize.