MPEG is a common video compression technique that identifies key frames stored as JPEG images and compares subsequent frames to store only the differences, achieving high compression. AVI can contain video compressed with different codecs and supports maximums of 30 fps and 320x240 resolution. MPEG and inter-frame compression look at previous frames to store differences, while intra-frame compression treats each frame individually like a JPEG. Animated GIFs display a series of frames with settings for delay, transparency, and looping.

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

8. Intra-frame and Inter-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)