ISDD Video Compression
- 2. Video Compression Uncompressed video has a very high data rate – over 100 Megabytes / second for HD An uncompressed movie file could be as large as a terabyte – a lot of data
- 3. MPEG One common technique (codec) for compressing video is MPEG (Motion Picture Experts Group). MPEG is the standard file format for DVDs because of the high compression ratio.
- 4. MPEG MPEG works by identifying key frames and storing all the key frame data as a JPEG comparing subsequent frames and storing only the changes in each frame At 24 fps, there is often very little change from one frame to the next. Frame 1 (key frame) Frame 2 Frame 3 Frame 4
- 5. AVI Audio Video Interleave Is a container file format so can actually contain video and audio compressed with different types of codec. Can contain compressed or uncompressed files Maximum frame rate 30 fps Maximum resolution 320 x 240
- 6. Intra-frame and Inter-frame Intra-frame Compression: Compressing individual frames For MPEG will be key frames, compressed as individual JPEG images Uncompressed AVI stores all frames in uncompressed format
- 7. Intra-frame and Inter-frame Inter-frame Compression: Look at key frame, then for key frame + 1 store only changes between the 2 frames Continue using this process of storing difference between current frame and previous frame, until next key frame
- 9. Animated GIF An animated GIF file is made up of a number of GIF frames displayed one after the other The animated GIF file stores the following settings: Frame delay - adjusts the amount of time between frames Transparency - each frame can have areas of transparency or for the whole animation Looping - specify how many times an animation will repeat (including none or forever)
- 10. Animated GIF An animated GIF file is made up of a number of GIF frames displayed one after the other The animated GIF file stores the following settings: Frame delay - adjusts the amount of time between frames Transparency - each frame can have areas of transparency or for the whole animation Looping - specify how many times an animation will repeat (including none or forever)