Introduction to JPEG and MPEG standard techniques
- 1. INTRODUCTION TO JPEG AND MPEG STANDARD PRESENTED BY:- SHALINI KUMARI
- 3. JPEG( JOINT PHOTOGRAPHIC EXPERTS GROUP) JPEG Compression is the name given to an algorithm developed by the Joint Photographic Experts Group whose purpose is to minimize the file size of photo-graphic image files. JPEG compression is a powerful tool, and with great power comes great responsibility.
- 4. While JPEG compression can help you greatly reduce the size of an image file, it can also compromise the quality of an image and if you aren’t careful, there may not be any recovery because it is lossy compression . Note: An image file can be thought of as a grid of individual blocks called pixels. Each pixel has its own color value, and the larger the image, the more pixels.
- 6. STEPS OF JPEG DATA COMPRESSION : STEPS-1 COLOR SPACE TRANSFORM In this phase, we convert R, G and B toY, Cb and Cr model. HereY is for brightness, Cb is color blueness and Cr stands for Color redness. We transform it into chromium colors as these are less sensitive to human eyes.
- 7. STEPS-2 SPLITTING In process of splitting, We split our image into the blocks of 8*8 blocks. It forms 64 pixels in one block.
- 8. STEP-3 APPLY DCT – We apply Direct cosine transform on each block from left to right ; top to bottom . The discrete cosine transform (DCT) represents an image as a sum of sinusoids of varying magnitudes and frequencies. It helps to reduce amount of data to represent the image while preserving important visual information. MORE ABOUT DCTON PAGE NO 14
- 9. STEP-4 QUANTIZATION In the Quantization process, we quantize or round-off our data using the quantization table. This also helps in reducing the amount of space needed by the initial image. Ex. Input=3.7 Output=4
- 10. STEP-5 SERIALIZATION In serialization, we perform the zig-zag scanning pattern to reduce no. of coded zero transform and to show high energy first then lower. Zig zag scanning will order the DCT frequencies so that ones with higher energy will appears first than lower after.
- 11. STEP-6 VECTORING We apply DPCM (differential pulse code modulation) on DC elements. DC elements are used to define the strength of colors and we perform run length encoding on AC components. The differential pulse code modulation is used to remove the unused bit in image.
- 12. STEP-7 ENTROPY ENCODING In the last stage, we apply to encode either run-length encoding or Huffman encoding. The main aim is to convert the image into text and by applying any encoding we convert it into binary form (0, 1) to compress the data. NOTE:-The AC and DC components refers to types of coefficient obtained from the discrete cosine transform DCT. The DC component represents the low frequency information and AC component represent the high frequency information
- 14. DISCRETE COSINETRANSFORM • It transform given block from given domain into frequency domain by separating images into parts of different frequencies. • It is used in lossy image compression • If we convert image into DCT it could higher frequencies to zero then convert back to image that’s why firstly convert image into 8*8 matrix. GO BACK TO STEP 3 Given domain Frequency domain
- 15. INTRODUCTIONTO MPEG • MPEG stands for moving picture experts group. • This compression is mainly is used for movies, T.V. shows, video clips on the web. • It have various standard for audio and video compression. • Compression is done on series of frames is with ratio 20:1 that can vary up to higher on video content. • The extension is given like .Mp3 and .Mp4 .
- 16. Thank you