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Video Data. Topic 4: Multimedia Technology. What is Video?. A video is just a collection of bit-mapped images that when played quickly one after another give the illusion of a moving image It is a sequence of individual pictures or frames

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Video data

Video Data

Topic 4: Multimedia Technology


What is video

What is Video?

  • A video is just a collection of bit-mapped images that when played quickly one after another give the illusion of a moving image

  • It is a sequence of individual pictures or frames

  • The standard rate at which these frames are taken is 25 frames per second (this gives realistic movement)


Input capture digital video camera camcorders

Input (Capture):Digital Video Camera (Camcorders)

  • Work in the same way as digital cameras

  • They use the same light sensors, called CCDs

  • They have a lower resolution than cameras

  • They are designed to capture lots of images (frames) fast


Input capture digital video camera camcorders1

Input (Capture):Digital Video Camera (Camcorders)


Input capture webcam

Input (Capture): Webcam

  • Designed for the purpose of creating videos to be transmitted over the Internet

  • They do not need to be high resolution, keeping down the bit rates and price.

  • They use low resolution array CCDs and low quality lenses, keeping costs down


Input capture video capture card

Input (Capture): Video Capture Card

  • A video capture card is needed to capture videos from analogue sources

    • video tape players, television broadcasts and analogue video recorders

  • Some modern graphics cards include the ability to capture video


Video data storage of video data

Video Data:Storage of Video data

Topic 4: Multimedia Technology:


Avi audio video interleave

AVI (Audio Video Interleave)

  • Type of RIFF file (container file)

  • Uncompressed

  • AVI ratio set during saving

    • The audio is embedded into the video at different intervals.


Video data

MPEG

  • Lossy compression cuts out unnecessary parts of a video clip

  • Saves each frame of video as a JPEG

    • These are called ‘i-frames’

  • Data that stays the same in following frames is removed

  • The next frames only store data on what has changed since last i-frame


Video data

MPEG


Mpeg standards

MPEG Standards

  • MPEG-1

    • VHS video quality with 353 x 240 pixels and 30 fps frame rate support

  • MPEG-2

    • The standard for DVD-Video and Digital Television

  • MPEG-3

    • Intended for HDTV but these revisions were incorporated into MPEG-2)

  • MPEG-4

    • Designed for low-bandwidth networks - e.g. video phones) (Part used by DivX

  • MPEG-7

    • Builds on the interactive and extra data capabilities of MPEG-4 and is a full multimedia description format


Video quality and file size

Video Quality And File Size

  • Colour depth:

    • Increasing colour depth improves quality and increases file sizes.

  • Resolution:

    • Increasing resolution improves quality and increases file sizes.

  • Frame rate:

    • Measured in frames per second (FPS).

    • Increasing frame rate increases file size. Lower frame rates reduce file size but make video clip ‘jerky’.


Video quality and file size1

Video Quality And File Size

  • Video time:

    • increasing or reducing the time of a video is the obvious way to affect the file size.

    • Quality of the display of the clip is not affected.

  • Lossy compression:

    • Using MP3 compression reduces file sizes without affecting quality.


Calculations

Calculations

File Size (Bytes) = Frame Size (Bytes) x Frame Rate (fps) x

Video Time (s)


Calculations1

Calculations


Video data video editing

Video Data:Video Editing

Topic 4: Multimedia Technology:


Timeline

Timeline

  • Each frame is displayed as a thumbnail image.

  • Each frame can be individually edited

  • The audio would also be on an timeline

  • Some packages provide multiple timelines


Storyboards

Storyboards

  • Simple plan of final product

  • Usually freehand and rough

  • Important process for all multimedia applications

  • Produced at Analysis stage


Video data

Crop

  • Basically, cutting or removing the parts you don’t want.

  • You may want to remove a frame or a whole scene.


Sequencing

BDCA

ABCD

Sequencing

  • Once you’ve got your video cropped, edited you have to put it in sequence.

  • In other words, put it in the correct order


Transitions

Transitions

  • Used to ‘join up’ different scenes/frames

  • Different types are available, for example:

    Wipe


Transitions1

Transitions

  • Used to ‘join up’ different scenes/frames

  • Different types are available, for example:

    Dissolve


Transitions2

Transitions

  • Used to ‘join up’ different scenes/frames

  • Different types are available, for example:

    Box Out


Transitions3

Transitions

  • Used to ‘join up’ different scenes/frames

  • Different types are available, for example:

    Fade


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