Chapter 3: Source Material

1
Chapter 3 Source Material

• COMP 2073
• Week 4
• Winter 2003
• Professor Kona Sirohi
• Email ksirohi_at_gbrownc.on.ca

2
Definitions of Audio and Video

• Video is a means of reproducing moving visual
  images by representing them with an analog
  electronic signal.
• The images are decomposed into a series of
  horizontal scan lines, so that they can be
  stored, transmitted and reproduced.
• Three major standards for video systems
• NTSC (National Television Standards Committee)
  -Screen resolution is 525 lines and refresh rate
  is 60 Hz.
• PAL(Phase alternation by line)- Screen resolution
  is 625 lines and refresh rate is 50 Hz
• SECAM(Sequential Color and Memory) - Screen
  resolution is 819 lines and refresh rate is 50 Hz.

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Definitions of Audio and Video(contd..)

• Audio is a sound with an electrical alternating
  current within the range 20 20,000 Hz(audible
  to the human ear).
• Audio plays an important role in the delivery of
  a successful video presentation.
• In computers, an audio card is required to listen
  to an audio. A audio card is contains special
  built-in processor and memory for producing audio
  files.
• Analog signals of sound are converted to digital
  by the audio card, using a microchip called
  analog-to digital converter (ADC).
• During playback, the digital signals are
  converted back to analog signals within the
  speakers to generate varied sound.

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Definitions of Audio and Video(contd..)

• Audio files are usually compressed for storage or
  faster transmission.
• Audio files can be sent in short stand-alone
  segments (.WAV format) or streaming format (.RAM
  format).
• Computers understand only digital audio format
  for playback.
• Digital tape formats and digital file formats are
  different in terms of the media used for storage
  and accessibility.

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Definitions of Audio and Video(contd..)

• To capture any media, you need
• A media source (a camera, microphone, VCR etc)
• A capture card a device that converts analog
  signals, such as those generated by a video
  camera, into a digital format. The video capture
  card also compresses the data.
• Software to convert digital feed into digital
  file or streaming file.

6
Video Formats

• A video format is a standard that determines the
  way a video signal is recorded by an analog or
  digital recording device on a video tape, and the
  type of playback system to be used for playback.
  Some standards are Digital 8, DV, Hi8, VHS etc.
• There are two types of video signals
• Component - the highest quality analog video
  because it can be divided into Y(Luminance
  signal), R-Y(Red) and B-Y(Blue). It gives a
  better picture detail with purer colors.
• Composite this type of signal contains all the
  information (luminance, color and synchronization
  info) needed for the color picture in a signal
  channel of information and cannot be broken down.
  Uses analog compression to combine the three
  channels of component signals into one single
  stream.

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Audio Formats

• In the past, the process of analog recording
  using long-playing records and tapes were slow
  and expensive.
• Each audio source was recorded onto a separate
  audio track and then mixed with other tracks.
• This method had no way of editing the audio track
  once recorded.
• Today, the MIDI (Musical Instrument Digital
  Interface) sequencers and sound cards allows
  anyone to create music right on his desktop.
• Songs can be downloaded as MIDI or MP3 files.
• Streaming files promises a wider, faster and more
  secure distribution of digital media.
• Some common digital audi formats are .AU, .AIFF,
  .MP3 etc.

8
Video Equipment

• Shooting a video has many components like props,
  light, sound, actors etc.
• Producing video for the web or streaming doesnt
  require high-end equipments.
• Streaming technology uses Internet Protocols to
  deliver the content over the network.
• Streaming servers distribute the signals and the
  clients over the network play them back.
• Commercial audiences can receive a streaming
  signal from 14 Kbps to 1 Mbps.
• Broadcast transmission signals have a bandwidth
  of 8 Mbps to 25 Mbps.

9
Video Equipment (Contd)

• Cameras such as Sony VX2000 or Canon XL1 or Sony
  DVCAM series video cameras offer superb recording
  quality for streaming video at a moderate rate.
• Desktop editing systems such as Adobe Premiere
  and Final Cut Pro provide low-cost editing
  solutions for media production.
• Purchasing mid-level to high-end production gear
  may be pretty costly specially for those who
  produce video only few times a year.

10
Light

• Any video-camera, not matter how advanced will
  produce poor results without proper light.
• Lighting for video is a complicated task and
  requires knowledge of both videography and
  general lighting techniques.
• The primary job is lighting is to bring the level
  of light up to a point at which an image can be
  produced on a piece of film or digital video
  chip.
• Professional studio lighting helps produce image
  with sharper edges, lower contrast, richer color
  and less noise.
• Images with these above qualities compress very
  well.

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Light (contd)

• To maximize the video output from the camera to
  the capture card, use diffused light, remove
  heavy lighting contrast and reduce harsh shadows.
• Add a background light to help separate the
  subject from the background.
• The following guidelines on the next slide can
  maximize the quality of a video content.

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Light (contd)

• Use a tripod.
• Avoid Camera movements.
• Avoid movement in the background.
• Add light to your subject.
• Use a close-up or a medium shot, so that the
  encoder has minimum amount of content to
  compress.
• Do not zoon-in or zoom-out.

13
Light (contd)

• A poorly lit subject would require extra
  processing when it is encoded and converted into
  streaming file.
• Lighting aspects are more noticeable when
  observed through a black and white or shaded
  environment.
• Try to use three-point lighting whenever
  possible.
• Key Light brightest, placed at a 45? angle on
  one side of the subject, slightly above the
  subject.
• Fill Light Opposite side of key, same height as
  the subject, bright enough to partially fill in
  the shadows.
• Back Light Above and behind the subject,
  separates subject from the background.

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Sound

• Broadcasting video with audio is very much
  different from broadcasting just audio.
• With a video and audio together, the audiences
  main attention is on the video.
• Creating an audio only broadcast has 2
  challenges
• Attract the audiences attention, generating
  interest without showing any moving images
• Keep up their attention with high-quality sound.

15
Sound(contd)

• Use all the possible resources to ensure the good
  capture, processing and distribution of your
  audio feed.
• Audio is an analog source and you would need to
  use a combination of analog and digital devices
  to capture and process audio feed.
• Live audio is captured using microphones.

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Microphones

• Microphones are devices that convert sound energy
  into electrical current or digital data.
• All microphones have a diaphragm, or membrane
  that vibrates in response to sound waves and
  converts them into electrical energy.
• Three kinds of microphone
• Condenser must be amplified extensively in
  order to be useful, very small and used as a
  clip-on for recording sound from musical
  instruments.
• Dynamic Unidirectional, relatively large,
  suitable for handheld operations, used for
  recording nearby sounds.
• Ribbon bi-directional, used to record voices in
  a conference room. Very sensitive and captures
  wind noise if not protected with a wind-flag.

17
Sound Mixer

• Once the microphones are in place and you are
  ready to start recording, you should first
  balance the sounds to emphasis the ones that the
  users would listen to.
• This is done by using a sound mixer.
• The sound mixer should have multiple input
  options, for microphone connections, playback
  devices or camera outputs.
• Level of sound is the relative strength of the
  signal measured in decibels (dB).
• Input all the sound sources to the mixer and
  balance the level of each source by using a
  good-quality microphone.
• The output from mixer is connected to the capture
  card on the encoding workstation.

18
Camera

• Video Cameras are electronic devices that capture
  and document life as it appears on the cameras
  optical lens.
• Cameras still cannot replicate what human eyes
  can see.
• Video cameras cost from 1,000 for a home video
  camera to 40,000 for a studio-broadcast quality
  camera.
• Streaming video files play back nicely if you
  have recorded the media with a Mini-DV or a DVCAM
  camera.

19
Camera(contd)

• A good camera must have the following functions
• White Balance Controls that strengthen the blue
  or red colors, allowing white objects to appear
  pure white.
• Manual zoom The ability to enlarge an image by
  manipulation of the lens elements to increase the
  size of the object.
• Manual Focus A control that helps the user
  select and focus certain subjects in the frame.
• Manual IRIS A control that helps the user to
  control the amount of light that enters the
  camera.
• S-Video output A connection that maximizes the
  camera output signal while capturing media on a
  computer.
• Color Viewfinder - A control that helps the
  camera operator balance color levels.

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Action
21
Action(contd)

• The encoding process performed on the content
  before packets were sent to the client determines
  the quality of a stream.
• Streaming media encoders take video and audio
  signals from the capture card.
• The capture card acts as a mediator, taking the
  video signals from its original analog or
  digital format, compresses it, and passing it on
  to the streaming media encoders.
• Till this point there is no degradation of
  quality except for the resizing and the
  compression process losses.
• Once the streaming encoder receives this feed, it
  converts this digital feed into streaming feed.

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Action(contd)

• Factors affecting the quality of the playback
• content
• The production process the light conditions,
  camera movements, audio levels, editing.
• The configurable options of the encoding process
  audio and video codecs, window size, assigned
  frames per second, pixel format, filters.
• The network condition
• The client computers configurations

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Action(contd)

• Rules to help in producing better content for
• Streaming video-
• Minimize changes and movement from frame to
  frame.
• Minimize the use of bright white, blues and
  yellows. The subject should wear solid colors.
  Any type of patterns around the subject would
  result in the degradation of the playback
  quality.
• Get your audio levels right. Use a mixer to mix
  and balance the audio content.
• Dont change the configurations of the audio and
  video settings of the capture card during a live
  broadcast.