Here we get to know about lossy compression techniques that are jpeg and mpeg . We also uses discrete cosine transform (DCT).

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.

5. Block diagram

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

13. Final results are:

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