Subject : multimedia

1. 
   What is Motion Video?
   

1. 
   Expand CIF
   

1. 
   What are the components of color video?
   

• 
  Luminance Components
  
• 
  2 Chrominance components
  

1. 
   Expand EDTV.
   

1. 
   Expand SMPTE.
   

1. 
   Expand EDI.
   

1. 
   Expand SCART
   

1. 
   What is video capture card?
   

1. 
   What are the two types of light sensitive cells?
   

1. 
   What are the chrominance parts?
   

1. 
   Write about analog video camera.
   

Analog video camera are used to record a succession of still images and then convert the brightness and color information of the images into electrical signals. These signals are transmitted from one place to another using cable or by wireless means and the television set at the receiving end these signals are again converted to form the images.

The tube type analog video camera is generally used in professional studios and uses electron beams to scan in a raster pattern, while the CCD video camera using a light sensitive electronic device called the CCD.

1. 
   Monochrome Video Camera:
   

The electron migrates towards a positive potential applied to the lens side of the target. This positive potential is applied to a thin layer of conductive but transparent material. The vacant energy states left by the liberated electrons called holes migrate towards the inner surface of the target.

Lens Target Element

Electron Gun

Electron Beam

Source Output

Charge

Separation

It essentially consists of three camera tubes in which each tube receives selectively filtered primary colors. Each camera tube develops a signal voltage proportional to the respective color intensity received by it. Light from the scene is processed by the objective lens system. The images formed by the lens are split into three images by glass prism. These prisms are designed as diachronic mirrors.

This mirror passes one wavelength and rejects other wavelengths, thus red, green, and blue images are formed. This generates the three color signal Vr, Vg, Vb the voltage levels of which are proportional to the intensity of the colored light falling on the specific tube.

.

1. 
   Write about Digital Video Standards.
   

Analog video has been used for years in recording/ editing studios and television broadcasting. For the purpose of incorporating video content in multimedia production video needs to be converted into the digital format.

Digital video on personal computer it is very difficult initially because of the huge file sizes required and secondly of the large bit rate and processing power required. It requires a video capture card and associated recording software. The digital output from a digital video camera can also be fed to a PC after necessary format conversion

DIGITAL VIDEO STANDARDS:

1. 
   Enhanced Definition Television System (EDTV):
   

The double multiplexed analog components a standard is designed as an intermediate standard for transition from current European analog standard to HDTV standard.

1. 
   CCIR (ITU-R) Recommendations:
   

It is the standard developed for digitizing the video signal. A color video signal has 3 components.

• 
  Luminance Components
  
• 
  2 Chrominance components
  

1. 
   Common Intermediate Format (CIF):
   

1. 
   Source Input Format:
   

1. 
   High Definition (HD) video and HDTV :
   

Some fields short using the HDTV include the following star ware Episode 2,3, spy kids 2 and spy kids 3D.

1. 
   Write a note on Video Editing.
   

1. 
   Online and Offline Editing:
   

1. 
   SMPTE Time Code:
   

Two methods are used to generate SMPTE time code in the video world.

• 
  Drop
  
• 
  Non-Drop.
  

1. 
   Time Base:
   

Time is a continuous flow of events video requires perfect synchronization. so it is necessary to measure the time using precise numbers. When editing video the source clips may need to be inserted to create the output clip. The source frame rates of the clips determine how many frames are displayed per second.

1. 
   Edit decision List (EDI):
   

1. 
   Give a short note on Chromo sampling.
   
2. 
   Chroma Sub sampling:
   

• 
  4:2:2
  

• 
  4:1:1
  

• 
  4:4:4
  

• 
  4:2:0
  

1. 
   Write about Video Signal Formats.
   

1. 
   Component Video:
   

1. 
   Composite Video:
   

The total bandwidth of the channel is split into separate portion and allotted for the luminance and chrominance parts. In some cases a SCART or BNC connector is used instead. Since a single wire carries different types of signals, a certain amounts of crosstalk or interface is introduced which leads to a slight degradation in video quality compared to component format.

1. 
   S-Video:
   

3

4

2

1 Ground

3 Luminance (Y)

4 Chrominance (C)

1. 
   SCART Connector:
   

The signal levels are around 1 volt so they are not much influenced by noise. It cannot carry both S-video and RGB signals at the same time. It cannot transmit surround sound formats and can only transmit analog signals not digital.

SCART connectors use coaxial cables to transmit audio and video signals, however cheaper versions may use plain wires resulting in degraded image quality.

Part C

1. 
   Write about transmission of video signals
   

A color video camera produces three color signals corresponding to the R, G, B components of the color image. These signals must be combined in a monitor to produce the original image. Such a scheme is suitable when the monitor is close to the camera and three cables could used to transmit the signals from the camera to the monitor.

It requires three separate cables or wires or channels which increase the cost of the setup for large distance. Secondly it was found difficult to transmit the cables at exact synchronism with each other so that they arrived at the same instant at the receiving end.

Thirdly for TV signals, the transmission scheme had to adapt to the existing monochrome TV transmission set up, i.e. the same signals would need to produce a monochrome image in B/W TV set and a color image in a color TV set. Due to these reason, a new format called YC format was developed which addressed all theses issues.

This format was based on the luminance chrominance principle which originates from the human visual perception of color.

Color Perception Curve:

All objects that we observe are focused sharply by the lens system of the human eye on the retina. The retina which is located at the back side of the eye has light sensitive cells which capture the visual sensation. The retina is connected to the optic nerve which conducts the light stimuli to the optical center of the brain.

The light sensitive cells are of two types-rods and cones. Rods provide brightness sensation and thus perceive objects in various shades of grey from black to white. The cones are sensitive to color and can broadly be classified into three different groups. One set of cones detect the presence of blue color, the second set perceives red color and the third is sensitive to the green shade.

Any color other than red, green and blue excite different sets of cones to generate a cumulative sensation of that color.

Relative Sensitivity

of eye

The reference white for color television transmission has been chosen to be mixture of 30% red, 59% green and 11% blue.

1. 
   Luminance and Chrominance:
   

The luminance components, describes the variation of perceived brightness by the HVS in different portions of the image without regard to any color information, e.g. an image with only luminance would be a grayscale image similar to that seen on a monochrome TV set. The luminance component is denoted by Y.

The chrominance component, describes the variation o color information in different parts of the image without regard to any brightness information. It is denoted by C and consists of two sub- components: hue (h) which is the actual color e.g. red. And Saturation (s) which denotes the purity of the color i.e. gray mixed with original color e.g. bright re, dull red etc.

1. 
   Generating YC signals from RGB:
   

To generate a perceptually realistic grayscale image, more emphasis should be allowed to the green component and least to the blue component. The relation between the Y and RGB which is used unanimously nowadays is shown as

Y= 0.3R + 0.59G + 0.11B

This states that the brightness of an image is composed of 30% of red information, 50% of green information and 11% of blue information. The C sub components i.e. H ands are quantitatively defined in terms of color difference signals referred to s blue chrominance Cb and red chrominance Cr. These are defined as:

Cb = B-Y

Cr = R-Y

The color difference signals are generated by inverting Y and adding the inverted signal separately to R and B to obtain (R-Y) or Cr and (B-y) or Cb.

The color difference signal equal zero when white or grey shades are being transmitted. The calculation is..,

For any grey shade (including white) let R=G=B=V volts.

Then Y=0.3v + 0.59V + 0.11V=v

Thus, (R-Y) =v-v=0 volt, and (B-Y) = v-v =0 volt.

Conversion of RGB signals into YC format also has another important advantage. When R, G and B voltages are not equal, the Y signal represents the monochrome equivalent of that color.

1. 
   Chroma Sub sampling:
   

• 
  4:2:2
  

• 
  4:1:1
  

• 
  4:4:4
  

• 
  4:2:0
  

1. 
   Write about Television Broadcasting Standards.
   

1. 
   National Television System Committee (NTSC):
   

The TV signals are transmitted with luminance as main signal and chrominance as apart. Out of the 525 lines only 480 lines is used actively for picture generation and other used for synchronization and vertical retrace. In color TV luminance signals takes the place of original monochrome signal used for black and white.

The chrominance part has 2 sub components I (In-phase) and Q (Quadrature). I and Q represent the amplitude modulated in quadrature on to the sub carrier wave. I represent orange and cyan access. Positive I represent Orange and the Negative I represent the Cyan. Where as Q represents Magenta and Green. Where positive Q represents Magenta and negative Q represents green.

Luminance is represented in Y is 30% of red, 59% of green, and 11% of blue. Relation is defined as

Y= 0.3R + 0.59C + 0.11B

I and Q can also be defined in terms of R, G and B as shown below.

I= 0.74Cr – 0.27Cb = 0.74(R-Y) - 0.27(B-Y) = 0.60R - 0.28G - 0.32B

Q= 0.48Cr + 0.41Cb = 0.48(R-Y) + 0.41(B-Y) = 0.21R - 0.52G + 0.31G

The video professionals and television engineers do not use these NTSC standards. Due to the specific reason during the signal propagation the phase relationship associated with color signals are liable to drift, resulting in incorrect hues at the receiver set.

1. 
   PAL (Phase Alteration Lines):
   

It uses 625 horizontal lines at 25 frames per second, 2:1interlacing with 2 fields per frames aspect ratio of 4:3. The PAL refers to that phase part of the color information is irrevised with each line that helps to correct the phase errors in transmission.

It gives better quality than NTSC. Out of the 625 lines 576 lines are actively used to display the image on the screen remaining is used for synchronization and vertical phase lines.

1. 
   Sequential Color and Memory (SECAM):
   

Fundamental difference is the former transmit 2 color signals simultaneously while the later transmit one color at a time. It gets information for the preceding color transmitted and stored in memory.

1. 
   Write about PC Video.
   

The analog video needs to be digitized before displaying on the PC screen. The conversion involves using 2 devices. Source and Source Devices.

1. 
   Sources and Source Devices:
   

The output conforms to one of the 2 standards- Components and the composite are the output standards and NTSC and PAL or sequence are the input standards. The source and source device can be one of the following.

• 
  Camcorder with pre recorded video tape
  
• 
  VCP with pre-recorded video cassette
  
• 
  Video camera with live footage.
  

1. 
   Video Capture Card:
   

• 
  Video INPUT port to accept the video signals from NTSC/PAL/SECAM broadcast signals, video camera or VCR.
  
• 
  Video compression- decompression hardware for video data.
  
• 
  Audio compression- decompression hardware for audio data.
  
• 
  A/D convertor to convert the analog input video signal to digital form.
  
• 
  Video OUTPUT port to feed output video to camera and VCR
  
• 
  D/A convertor to convert the digital video data to analog signal for feeding to output analog devices.
  
• 
  Audio INPUT/OUPUT ports for audio input and output functions.
  

1. 
   Video Capture Software:
   

1. 
   Write about Video File Formats and Codecs.
   

1. 
   AVI (Audio/Video Interleaved):
   

1. 
   MOV (QuickTime Movie):
   

1. 
   MPEG (Motion Picture Experts Group):
   

MPEG-2 is designed for DVD applications and provides a quality comparable to SVHS quality. MPEG-4 provides an efficient method of object oriented content based storage and retrieval of multimedia content. MPEG-7 is a scheme for description of the multimedia content through media objects may be retrieved queries.

1. 
   Real Video:
   

Helix Player is the open source media player built on top of helix DNA client for Linux and other operating system. The helix player contains supports for the following media formats.

1. 
   Indeo Video Interactive:
   

Full used of these feature requires utility software available separately from Intel.

1. 
   Cinepak:
   

1. 
   Nero Digital:
   

1. 
   FFmpeg:
   

It is a set of open source computer programs that can be record, convert and stream digital audio and video. The project is made of several components.

• 
  ffmpeg: it is a command line tool to convert one video file format to another
  
• 
  ffserver: It is an HTTP multimedia streaming server for live broadcast. Time shifting of live broadcast is also supported.
  
• 
  Ffplay: It is simple media player based on SDL (simple direct media Layer) and on the FFmpeg libraries.
  
• 
  Libavcodec: It is library containing all the ffmpeg audio/video encoders and decoders.
  
• 
  Libavformat: It is a library containing parsers and generators for all common audio/ video formats.
  

1. 
   Write about Video Recording Formats and Systems.
   

1. 
   Ampex: (Alexander M Pontaiff Excellence)
   

1967, ABC used Ampex recorders for the first time to display instant slow motion replay of sporting events. In 1970, Ampex introduced the first robotic library system which enabled TV stations to re-sequence TV commercials instantaneously.

1. 
   VERA:
   

1. 
   U-matic:
   

1. 
   Betamax:
   

It is compared with the cheaper VHS cassette might be a relevant factor for its unacceptability in the home sector.

1. 
   Betacam:
   

A family of 1/2" videotape formats developed by Sony from 1982 onwards. Betacam-SP was developed which increased the resolution to 340 lines and became the industry standard for most TV stations. Digital betacame was launched in 1993, and replaced both Betacam and Betacam-SP. running times of S cassette is about 40 minutes while for L cassette it is about 124 minutes. It also implements support for serial digital interface coaxial digital connections.

Color different types of cassette identify their types: Betacam and Betacam-SP tapes are grey, digital Betacam tapes are light blue, Betacam SX tapes are yellow, MPEG IMX tapes are light green and HDCAM/HDCAM-SR tapes are black.

1. 
   Video Home System (VHS):
   

A linear control track at the tape’s lower edges, holds pulse that mark the beginning of every frame of video; these are use to fine tune the tape speed during playback and to get the rotating heads exactly on their helical tracks rather than having them end up some where between two adjacent tracks.

1. 
   Video Cassette Recorder(VCR):
   

1. 
   Video 2000:
   

1. 
   Video Compact Cassette (VCC):
   

1. 
   Camcorder:
   

1. 
   Explain about Video Editing Software.
   

1. 
   Importing Clips:
   

1. 
   Timeline Structure:
   

A playback head moves along the timeline from left to right, and the portion of the video data under the head is played back in a separate playback or monitor window.

1. 
   Playback of Clips:
   

1. 
   Trimming Clips:
   

1. 
   Splitting a Clip:
   

1. 
   Manipulating the Audio Content:
   

1. 
   Adding Transition:
   

1. 
   Changing the speed of a Clip:
   

1. 
   Changing the Opacity of a Clip:
   

1. 
   Applying Special Effects:
   

1. 
   Superimposing an Image:
   

1. 
   Exporting a Movie: