Digitization of Vedio and Adiou

8/6/2019 Digitization of Vedio and Adiou

http://slidepdf.com/reader/full/digitization-of-vedio-and-adiou 1/41

Digitization Of Audio And Video

� M.Umar Khan

� Bc-01083-013



Digitization

� Digitization is the process of convertinginformation into a digital format . In thisformat, information is organized into discreteunits of data called bits that can be separately

addressed (usually in multiple-bit groupscalled bytes). This is the binary data thatcomputers and many devices with computingcapacity such as digital cameras can process.



C omponents of Information

� Alphanumeric data

� Image� Audio

� Video



Digitization of Information� Information need to be digitized for

computer processing and thetransmission of information



Digital Information Processing

Data

Audio

Image

Video

DigitizedandEncoded

DigitalTransmission



T

he Advantages of Digitization� Information can be processed by the

computer

� Easy transmission of information overthe Internet and other computernetworks

� Minimize loss of quality duringtransmission



Digitization Of Audio



Digitization Of Audio: Overview

� Take samples of audio at pre-determined time intervals known as the

sampling rate� Represent the sampled audio with

digital signals

² Pulse Amplitude Modulation (PAM)

� Encode signals into binary code

² Pulse Code Modulation (PCM) thatincorporates PAM as well

² Required for computer processing



Digitization of Audio: Pulse

Amplitude Modulation (PAM)Audio

9 8 7 6 7 9

Digital Signals mustfurther be encodedinto binary signalsfor computerprocessing and

transmission.

Sampling Interval



Digitization and Encoding of Audio:

PulseC

ode Modulation (PC

M)� PCM is a two step process

� First the audio is sampled andrepresented by digital signals

� The digital signals are then encoded inbinary form



Binary Encoding of Signals in

Pulse C ode Modulation (PC M)

9 8 7 6 5 6

1001 1000 0111 0110 0101 0110

The integer numbers have effectively beencoded into zeros and ones. The ones and zerosnow contain the audio information encoded ina form that could be processed by a computer.

PCM



Salient Points on the

Digitization Of Audio� Sampling rate and the number of bits

used for representing the samples willdetermine the quality of the audio

� Quality is retained in transmissionbecause only codes are transmitted

� Audio can be recreated to the originalquality by extracting the pattern fromthe digital code



Sampling Factors� Sampling interval determined by

sampling frequency

² Measured in Hz

� Sampling depth

² Measured in bits

� Sampling channels

² Mono or stereo, for example



Factors Affecting Quality

Number of bits used for binary encoding.Example: 4 bits

allow 16amplitudevariations to berepresented.

9 8 7 6 7 9

Sampling Interval



Problem Representation

79 68 57 46 57 79

1/8000 Seconds (8000 HZ twice the frequency of the voicegrade circuit) or 2X4000 samples per second

8 bits are used enabling 256 amplitudes to

represent the human voice which is considered to be adequate.



Audio File Format� wav file format

² Basic file format in audio storage or raw file

� rm file format² Real audio·s streamed file format² Streamed file

� wma file format² Microsoft·s audio streamed file format² Streamed file

� mp3 file format² Compressed file

� aac file format²



Quality Retention� Quality is retained in digital

transmission because only the codes aretransmitted

� Quality is subject to some deteriorationin analog transmission because the

wave pattern is transmitted



Analog Audio T ransmission

Audio Priorto Transmission

Audio withInterference

Transmission

Audio After Filtering



Recreation of Audio from Analog

Signals� A difficult task

� Complex algorithms are used to filternoise etc. for better audio transmission



Digital Advantage in Audio

T ransmission� Only codes are transmitted

� Original encoding is recreated� Original audio is reproduced

� Again, sampling rate and number of

bits used in each sample will determinethe quality of audio transmitted



Digitization Of Image



Image Digitization� Image can be of the form black and

white, gray scales, color

� Factors that influence the digitization ofimage are as follows

² Resolution measured in pixels

² Color depth expressed in number of colorvariations



Digitization Of Image:Overview

PixelHorizontal Resolution



Digitization of the Letter L

Number of bits

determine the amount of

information that could

be stored.



Digitization Of Image: T he

Process� Divide the image into a grid of pixels

that may be considered as the samplingpoints of the image

� Digitize information on each pixel

� Store and transmit



Resolution

� Horizontal resolution

² Number of horizontal pixels

� Vertical resolution

² Number of vertical pixels

� Image resolution

² Horizontal by vertical resolution

² Ex: 640 by 480



Digitization of Black and White

Image� White

² A pixel lit represents a 1

� Black² A pixel not lit represents a 0

� Storage required per pixel² 1 bit

� Storage required for 640 by 480resolution image² 640 times 480 bits = 307,200 bits = 38.4K

Bytes



Digitization of Image Using

Gray Scales� A pixel may take a value between 0 and

15 for 16 gray scales

� A gray scale of 3 can be coded as 0011and the others similarly using this 4digit code

� The bandwidth requirement for thetransmission of a 640X480 image in thiscase is as follows:

² 640X480X4 = 153.5K Bytes



Bandwidth C omputation for

Image with 256C

olors� Resolution is 640X480

� 8 bits are required to represent 256colors

� bandwidth requirement for thetransmission of one image is as follows:

² 640X480X8 = 307.2K Bytes



C ompression of Digitized Images

� Compression is required to reduce thesize of the image file

� Large blocks of unchanged data in animage (background) offers anopportunity to compress the image

� Image files are almost alwayscompressed



A FewC

ompression Formats� GIF

� JPEG� MIC (Microsoft Image Composer)

� PCD (KODAK) - Used by Corel

� Uncompressed file exist in the form ofbit mapped file with the extension of.BMP



Image File Format Extensions

� File formats often represent the compressionprocedure being used such as jpgrepresenting the jpeg compression technique

� Examples:² Bmp ² uncompressed file format² Gif² jpg

² pcd² tiff² pcx



Digitization of Video� Digitization of video is an extension of

the process of digitizing an image

� It amounts to the transmission ofcertain number of still images known asframes per second

� Obviously, digitized video requireshigher bandwidth for transmission andmore space for storage



Frame Rate

� 30 frames of images per second, in general,defines continuos motion

� In communications, 25 frames per second isconsidered to be continuous motion

� 15 frames per second is currently used invideo conferencing over digital lines for

acceptable reception of video� It is also possible to engage in video

conferencing at a frame rate of 5 frames persecond



C omputation of Bandwidth for Raw T ransmission of Video

� Image resolution is 640X480

� Number of colors is 256 (8 bit)� Acceptable reception requires 15 framesper second

� Therefore, the bandwidth for the rawtransmission is as follows:

² 640X480X8X15 = 36.86M bps = 4.6M Bps



C ompression Standards Used in

the Digitization of Video� MPEG 1, MPEG 2, MPEG 3 and MPEG 4

� Windows Media Video

� Real Media

� Indio

� QuickTime

� ActiveMovie� AVI



Overview of Video T ransmission

in VideoC

onferencing� Minimum speed

² 3 to 5 frames per second

� Acceptable speed

² 15 frames per second

� Transmission techniques

² Data is compressed

² Only changes to the frame are transmitted



Bandwidth Optimization in

VideoC

onferencing� Minimize Windows for maximum

efficiency

² Transmit less number of pixels inminimized form

� Decrease the resolution² Has the same effect as above

� Decrease the number of colorsdisplayed



Video C onferencing Products

� Intel ProShare

� CU-See Me� Picturetel

� C-phone

� etc.

Digitization of Vedio and Adiou

Documents

Transcript of Digitization of Vedio and Adiou