5040_L10 ppt based on ofdm ystem

8/22/2019 5040_L10 ppt based on ofdm ystem

1/44

1

DATA AND FILE FORMATS

Data and file format standardization is crucial for

sharing of data among multiple applications and for

exchanging information between applications.Personal - computer(PC) industry has generated many

different standards. Text based file and data formats have

been replaced by multifunction formats which can

handle graphics, audio, video and color images.

A few of the commonly used data and file formats are:

1. Rich Text Format ( RTF)


2/44

2

Early text editors could not carry through formatting

information when transmitting files. This limited data

interchange because when text was moved from oneapplication to other, all the formatting information was

lost and had to be re- entered.

The RTF format extended this range of information. RTF

is capable to handle binary files, audio files and video

files to a certain extent.

2. Tagged Image File Format ( TIFF)

Tagged Image File Format has been around for a long

time. In this format, tags are used to keep all the attribute

information in a standard manner.


3/44

3

TIFF file provides tags that store information about

resolution of the image, fonts, format color, compression

scheme, date and time of capture, decompression, etc. A search through file is quick since these can be found

easily.

In case you have to extend the file, it is done throughpointers and links. And by creating extra blocks.

This approach represents industry standard to represent

raster image data generated by scanners, frame grabbersand paint/photo retouching applications.

It can represent color images in different types

representations. This standard can handle color images

very well.


4/44

4

3. Resource Interchange File Format (RIFF)

RIFF is not really a new file format. Rather, it provides

a framework for multimedia file format for Microsoftwindows based applications.

It can be used to convert a custom file format into a

RIFF format and transmit the file. For example a MIDIfile format is converted to RIFF by adding the RIFF

structure around it. Information is in blocks - called

chunks.

Like TIFF, RIFF is a tagged file format and uses tags to

store information in the header, about the file.

RIFF can handle MIDI, DIB, PAL, AVI files.

MIDI - is musical instrument di ital interface form.


5/44

5

DIB: Device Independent Bit-Map file

It can synchronize audio and vidio in movies.

Other commonly used format are:

4. Joint Photographic Expert Group (JPEG) - DIB

Format for Motion Images

Microsoft has extended the DIB file format for bothJPEG still and motion images. This can be used with

RIFF and AVI file format.

5. Motion Pictures Expert Group (MPEG) FormatMPEG1, MPEG2 are existing standards

6. Audio-Video interlaced file format ( AVI)

7. TWAIN Format ( for multimedia applications).


6/44

6

Multi-Media Input/Output Technologies

Multimedia can mean different things. It can be an

encyclopedia on a CD-ROM or a hypermedia messagecomposed by a user consisting of text, images, full

motion video.

Hypermedia links allow tracking of a subject matterthrough a variety of topics.

It takes specialized equipment to capture and store

multimedia objects.

Keyboard has been traditional input device for entering

data into computer system. It has changed from simple

numeric device to alphanumeric and multifunction

device over the years.


7/44

7

With the advent of GUIs, pointing devices, such as

mouse or a pen, have become essential for selecting or

moving graphical objects. Window based GUIapplications require a mouse or pen for selecting

various objects, push buttons, data entry boxes, so on.

In addition to traditional alphanumeric data entry,

multimedia technology requires a variety of other

types data inputs including voice or audio, full motion

video, still photos and images. These inputs require

special devices such as digital pens, audio equipment,

video cameras, and image scanners.

In case of text, there was no measure of quality. Text

was stored in ASCII/EBCIDIC formats. Now with


8/44

8

higher quality multi-font printers, the text quality is

measured in terms of print matrix resolution, text

color, font types, etc. The text capturing device does

not determine the end quality of the text.

Multimedia objects such as images, audio and video

depend on input device and storage for quality.

However, the capture device determine the outerbound of the quality. The display device, at best, can

match the resolution of capturing device.

Digital verses Analog Inputs

Another important distinction with multimedia objects

is the need to convert data from analog to digital form.


9/44

9

For example a scanner scans an object into scan lines and

pixels and then converts analog amplitude of each pixel

into a digital measure.0 or 1 for black and white.

0 - 255 for gray scale pixel points.

HSI or RGB for color objects.

TV signal ( NTSC) is also analog. It needs to be

converted into digital form for use in computer system.

The process for converting analog to digital and digital toanalog are called as coding and decoding.

Hardware devices and software programs for this

implementation are called as codecs.


10/44

10

Codecs usually include compressions and decompression

algorithms.

Different codecs are required for each type of multimediainputs.

Display and Encoding Technologies

Since multimedia systems include a variety of object types,

a number of different technologies are required for

compression, decompression and display of multimedia

objects.

Almost all multimedia objects are based on a graphical user

interface (GUI). Most graphical user interface are based on

VGA ( 640x480 pixels) or SVGA (800 x 600 pixels)


11/44

11

or even XVGA(1280 x 1024 pixels). Some imaging

applications may require 150 - 200 pixels per inch or

better resolution.

Voice mail system store analog sound and are usually

based on adaptive differential PCM technology. Codecs

are required for converting analog sound to digital

formats such as WAVE or AVI.

Video cameras provide input in analog formats such as

NTSC ( national television system committee ) standard,

PAL ( phase alteration line standard) or SECAM (France). Input from either source must be encoded to

digital format and decoded for transfer back for analog

play back.

Encoded compressed digital signals are based on JPEG or


12/44

12

MPEG standards. Other formats include AVI and RIFF.

Resolution and Bandwidth Issues

Each object type has some resolution. Images are

measured in pixels per inch. Higher the resolution, better

the object quality.

For document imaging systems, screen resolution of 100

pixels per inch ( ppi) are required.

The quality of 200 ppi is very good.

Laser printers and office copiers can provide a

quality of 300 - 600 ppi.

Published ( professional quality books) have

resolution of 1200-1800 ppi.


13/44

13

Sound quality is measured in terms of sampling rate and

number of bits used for representing magnitude of the

sample.

A higher sampling rate allows capturing of higher

frequency details.

Higher number of bits allow capturing of amplitudechanges more accurately.

Both factors contribute to the tone quality.

A sampling rate of 4 kHz at 8 bits is considered asminimal acceptable for voice grade sound.

A sampling rate of 8kHz at 16 bits is required for

music quality.


14/44

14

For CD-quality stereo sound, the sampling rate of

44.1kHz at 16 bits is required.

Multi-channel stereophonic sound requires evenhigher resolution.

The VCR quality is considered a minimum for video

display which is defined as

300 lines visible on the screen. The minimum

acceptable resolution is 320 x 240 pixels.

HDTV quality is 1280 x 1024 pixel range

Another measure of video quality is number of bits being

used for color definition. A 16 bit palette is common.

Higher color resolution is required for HDTV quality.


15/44

15

This will be 24 bit colors ( full color).

A third measure is the number of frames per seconds.

TV operates at 60 FPS

page 192.

Multimedia Object Quality and Transmission Bandwidth


16/44

16

Multimedia Input and Output Devices

Electric Pen

When an electric pen is used to write or draw, the digitizer

encodes the x and y coordinates of the pen, and the pen

status, which includes whether the pen is touching the

digitizer surface ( usually the screen) or not, pen pressure,pen angle, rotation, etc.

Most electric pen contain a micro-switch at the tip that

behaves like left button on the mouse. Some pens arecapable of measuring accurate pen pressure while others

can measure the proximity.

Pen computing requires generating x-y coordinates at least


17/44

17

120 times per second with 200 dpi resolution. The

minimum sampling rate generates sufficient data to track

pen movement.

Most pen digitizers produce an accuracy of 0.005 to 0.02

inch resolution. Resolution is defined as the number of

points digitizer is able to digitize in one inch.

Video and Image Display Systems

TV is video technology. Live pictures bring reality in our

environment. They educate us.

Introduction of video game took younger generation by a

storm.


18/44

18

Virtual reality will be the next major advance in game

technology, in military technology, and in training

environment.

VGA, SVGA, XVGA, 8514A, are some of the existing

video technologies.

Display Performance Issues

There are three main factors that affect the performance:

1. Network bandwidth: the play back becomes choppy and

incoherent if the bandwidth is insufficient to supportminimum data rate. There are JPEG and MPEG standards

to define this parameter.

2. Decompression or Decoding: once again, while in the


19/44

19

case of poor decompression, performance causes irritation

delays. In case of full motion video, poor decompression

causes same effect as poor network bandwidth.

3. Performance of Display Technology: if the technology

is not appropriate, the device may not display full motion

or graphics properly.

Tables show various video standards.


20/44

20


21/44

21


22/44

22

Typically, 14 inches monitors have active display area

of 9.875 x 7.125 and diagonal of 12.25.

If we assume a resolution of 1024 x 768, the dot pitchcan be defined as ( distance between two pixels):

0.24mmmm25.4x768

7.125dp(v)

0.24mmmm25.4x

1024

9.875dp(h)

This means that to display a resolution of 1024 x 768

very clearly, we need a 0.24 mm dot pitch monitor.Most 14-inch monitors come in 0.28 - 0.30 mm dp.

When these monitors display 1024 x 768 pixels, the

accuracy and crispness are compromised.


23/44

23

Now let us repeat the same calculations for a 17-inch

monitor which has 12.9 x 9.76 size with a diagonal of

16.125 inchesThe dp for 1024 x 768 pixels will be

0.32mmmm25.4x768

9.675

dp(v)

0.32mmmm25.4x1024

12.90dp(h)

This means to display a resolution of 1024 x 768 on a 17-

inch monitor, you would require a dp of 0.32 or better.

Most of the 17-inch monitors have a dot pitch of 0.28-

0.30. This is sufficient even to display a resolution of

1280 x 1024.


24/44

24

Smaller dot pitch gives a perception of clearer picture.

Horizontal Refresh Rate: is a measure of the rate at

which scan lines are painted. It is measured in kHz anda standard VGA monitor has a horizontal refresh rate

of 31.5 kHz

Vertical Refresh Rate: is closely tied to horizontal

refresh rate. It the rate at which whole screen is painted

( counting all scan lines) and return to the top of the

screen.


25/44

25

It is measured in Hertz. Typically it is 50-72 Hz.

Human eye is sensitive to lower vertical refresh rates

and is more likely to perceive flicker at lower rate. Itcan be annoying and tiring to eyes.

Print Output Technologies

Laser print technology has continued to evolve and print

quality at 600 dpi is starting to make this technology

useful for high speed process.

Offset printer resolution is around 1200 - 1800 dpi. 600dpi is sufficient for common print applications.

Digital Voice and Audio

Multimedia technology is multidimensional and audio is


26/44

26

Comparison of Print Technologies

f th di i th t dd i i d d


27/44

27

one of the dimensions that adds voice, music and sound

capabilities.

Until 1990, PC applications were visuals. Game

applications added voice/music dimension.

Today, some applications utilize sound boards whereby

audio inputs may be through keyboards, microphones, etc.

Digital Audio

When voice or music is captured by a microphone, it

generates electrical signal.

The signal consists of fundamental sine wave with

certain frequency and amplitude.

The fundamental sine wave is accompanied by

harmonics.


28/44

28

Adding the fundamental to harmonics, forms a composite

sinusoidal signal that represents the original sound.

Analog sinusoidal waveforms are converted to digitalformat by feeding the analog signal to A/D converter

(ADC) where the analog signal goes through the

sampling process.

Sampling Process:

The analog signal is sampled over time at regular

intervals to obtain amplitudes of the signal at

sampling time.

The regular interval at which sampling occurs is

called the sampling rate


29/44

29

Time

Voltage

T1

timesample

1rateSampling

T = Time interval between two samples


30/44

30

The sample amplitude obtained at sampling

instants is represented by an 8-bit value (one byte)

or 16-bit (two bytes) value.

Higher values can also be used for higher

resolution systems ( high fidelity sound).

A composite signal of 11.025 kHz sampled 4times every cycle will yield 44.1 kHz sampling

rate. If you sample at higher rate, you need to store

more samples.

For CD quality music at 44.1 kHz rate at 16-bit

resolution, a one minute recording will require

44.1 x 1000 x 16 x 60 / 8 = 5.292 Mbytes.


31/44

31

Audio objects generate a large volume of data. This poses

two problems.

First, it requires a large volume on disk space to store, and

Second, it takes longer to transmit this data.

To solve these problems, the data is compressed.

Compression helps shrinks the volume of data and less

disk space is required. It also helps to reduce network

time.

Audio industry uses 5.0125kHz, 22.05kHz and 44.1kHzas standard sampling frequencies. These frequencies are

supported by most of the sound cards.


32/44

32

Digital Camera

Digital cameras are being used increasingly for

multimedia applications due to internet advantage theyprovide in applications where very high resolution is not

required. The advantages are:

Digital images can be viewed immediately forproofing

Digital images can be printed immediately and any

number of times for duplications

Digital images can be integrated with word-

processor documents

Can be embedded in emails or faxed by computers.


33/44

33

Can be enhanced/altered for effective presentations

Can be archived - minimizing the risk of loss ordamage to the image.

Can take images of 3-D objects and store as 3-D

images

Digital cameras are portable and can be used in

environment where film cameras can not be used.

Possible uses: for fingerprint analysis, for driverslicenses, insurance companies, bank-customers

signatures, security installations, etc.


34/44

34

Full Motion Video

Although video image processing is not very common for

full motion video, there is no reason why it will not bedone in future.

Video capture circuit cards capture from

NTSC/PAL/SECAM signals from video cameras orVCRs or even s-video inputs ( RS 170 inputs).

Video capture boards can handle audio signals as well,

they can convert analog signals to digital (ADC) anddigital to analog forms(DAC)

Normally, a video capture board is used to capture real-

time video, and the digitized raw data is then compressed

in real-time.


35/44

35

The compressed data is subsequently moved to CPU

over ISA or local bus. The CPU then builds the AVI file

format for the compressed data and stores the file.

During the playback, the file is read in blocks by the

CPU, and the data is decompressed as blocks of audio

and video.

The data can be decompressed in either software or

hardware and sent to VGA card for display.

To understand performance issues, let us take an

example: calculate the bandwidth required to display a

real-time video at 640 x 480 resolution at 30 Hz frame

rate in true 24-bit color.


36/44

36

Bus Bandwidth

The bandwidth required for display of full motion video

is- resolution x frames per sec x pixels per bit for color.640 x 480 x 30 x 24 = 27.648 Mbytes/sec

This bandwidth is required to display real-time video in

true color 24-bit per pixel mode.

If you want to reduce from full color mode to 256

colors only ( 8-bit color), the bandwidth requirement

will reduce to 9.216 Mbytes/secThe ISA bus operates at 8 MHz and has a bandwidth of

2 Mbytes/sec, which is not sufficient for above

application. This gives you following options:


37/44

37

Display a video window of 300x200 at 30 frames per

seconds with 256 colors.

300x200x30 x 8 = 1.98 Mbytes/sec Display the video window at full VGA resolution of

640 x 480 at 6 frames per second with 256 colors.

640 x 480 x 6 x 8 = 1.84 Mbytes/sec

It is clear that ISA bus is a big bottleneck. However, the bus

bandwidth problem can be solved by using other bus

architectures, such as local bus, VESA, VL bus or PCI bus.Both VL and PCI buses have bandwidth in excess of

100Mbits per second. In theory, local bus operates at CPU

speed.


38/44

38

To achieve good performance, every link in the chain for

capture and playback must be examined carefully to

ensure that the required bandwidth can be carried bythat link, be it network, video server, compression or

decompression hardware or even display system.

Animation:

It is an illusion of movement created by sequentially

playing still image frames at a rate of 15-20 frames per

second ( close to full-motion video range).

Animation film contains a series of frames with

incremental movement of objects in each frame. It may

not be necessary to move objects to create the illusion of

movement. Color and background can be changed from


39/44

39

frame to frame so that there is perception of moving

object.

MEMORY SYSTEMS

Memory systems for computers have been changing to

meet the needs of high resolution graphic displays. The

demand on memory systems will even be greater with theincreased use of multimedia applications.

Memory Types

Different types of memories are used for differentpurposes due to retention factors, performance parameters,

and cost trade-offs.


40/44

40

Memory types that may be used in multimedia systems

include the following:

1. ROM (read only memory): is read only.Instructions and/or data is burned into the memory

permanently, and the contents are non-volatile.

ROM is used for firmware. That is: for operating

systems, software programs that have to residepermanently inside computer.

2. PROM (Programmable ROM): is semiconductor

memory that contains an array of fuses. These fusesare blown according to the word to be programmed.

To program, a specialized PROM programmer

(PROM burner) is used. This burner blows the fuse.


41/44

41

The contents of this PROM are non-volatile. The

access to PROM is random. Typical data-path is

16-bits wide.

3. RAM (Random Access Memory): is also

semiconductor type of memory that allows

random access to its contents.That is, the word

can be accessed by directly addressing it.

It is organized in an array form so that it can be

read and written efficiently. All words are

addressable. There are several types of RAMs:

SRAM (static RAM): It is semiconductor

memory consisting of transistors which can

remember the information.


42/44

42

These transistors do not require periodic charging

to maintain the information. It is read/write type.

The organization is array type to facilitate read andwrite operations. SRAM access speed ranges from

a few nanoseconds to 30 nanoseconds.

SRAM is volatile and loses the information when

power is switched off.

4. DRAM (Dynamic RAM): it is semiconductor

memory where information is stored in a

capacitor. The term dynamic is used becausecapacitors require periodic charging to maintain

the information. This process is known as periodic

refreshing.


43/44

43

Capacitors are used as memory cells and can

achieve high cell density.

The trade-off to high density is periodic refresh.DRAM is mainly used as main memory of the

computer. The access speed ranges 50-80 ns. It is

volatile and the information is lost if no power or

no refresh.

5. VRAM ( Video RAM): It is like DRAM. The only

difference is that it is dual-ported. The CPU port (

processor port) is standard port, similar to DRAM,containing data path and address path. In addition,

there is a video port. The video port contains a

buffer to hold a complete row of data.


44/44

44

This buffer is organized in such a way that it can hold

a complete data for a horizontal line. Each horizontal

line represents one row of the screen data.

The advantage of the VRAM is that the whole

horizontal line of video screen information is loaded

into the buffer in one scoop.

Buffers output is then converted from parallel to

serial and output as a video stream.

With dual porting screen, updates can be done in

almost half the time.

With VRAM, the port to the CPU is available 90% of

the time to do the updates.

Documents

5040_L10 ppt based on ofdm ystem