• Share
  • Email
  • Embed
  • Like
  • Save
  • Private Content
The memory of graphics
 

The memory of graphics

on

  • 246 views

Detailing the various calculations that are used to estimate storage requirements of various multimedia types

Detailing the various calculations that are used to estimate storage requirements of various multimedia types

Statistics

Views

Total Views
246
Views on SlideShare
246
Embed Views
0

Actions

Likes
0
Downloads
1
Comments
0

0 Embeds 0

No embeds

Accessibility

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

    The memory of graphics The memory of graphics Presentation Transcript

    • The Memory of GraphicsThe Memory of Graphics (Calculations involved in(Calculations involved in displaying multimedia)displaying multimedia)
    • • Images place extra demands upon multimedia systems. • The current image being displayed is stored in a section of memory called the frame buffer. • Large, high resolution images may affect the performance of a multimedia presentation. • The relationship between the image on the screen and the bits in memory is called bit mapping or memory mapping.
    • • The storage requirements of an image are dependent upon: • the number of pixels • the number of colours / tones • Bit depth is the number of bits required per pixel. • Each extra bit per pixel doubles the number of possible tones or colours. • [COPY Table 7.1, p.223]
    • • To calculate the size of an image we must multiply the number of pixels by the bit depth. • E.g. What is the size in kilobytes of a 256 colour image displayed on a screen with a resolution of 1024 x 768 pixels. • File size = dimensions x bit depth = 1024 x 768 x 8 / 8 x 1024 = 768 Kb.
    • • Video of any kind is just a series of still images that are played one after the other. • This means that to calculate the memory requirements of any video/animation we expand upon the formula we already have. • We use the file size for one image multiplied by the number of frames per second (frame rate) multiplied by how many seconds of video there is.
    • • E.g. What is the file size, in gigabytes, for a 90 minute video in 32 bit colour with a resolution of 2048 x 872 being broadcast at 24 fps? • Number of frames = frame rate x seconds = 24 x 90 x 60 = 129 600 frames • Frame file size = resolution x bit depth = 2048 x 872 x 32 • Total size = 24 x 90 x 60 x 2048 x 872 x 32 / 8 x 1024 x 1024 x 1024
    • • Audio files are different because of how they are displayed. • All sound must be converted from an analog to digital form. • This digitisation of sound is called sampling. • The quality of the sound is determined by its sampling rate and sample size, as well as whether the sound is mono or stereo. • The sampling rate is the number of times a slice (sample) is taken of a sound wave per second.
    • • Two common sampling rates are 44.1 kHz (44100 samples per second) and 22.05 kHz (22050 samples per second). • The more samples, the better the sound. • The sample size is the number of bits per sample. • The more bits per sample, the higher the quality. • Two common bit-rates are 8 bit and 16 bit sound.
    • • Stereo requires two audio streams while mono only needs one. • E.g. Calculate the file size (in Mb) of a three minute stereo audio track that has been recorded using 16 bit sound and a sampling rate of 44.1kHz. • = sample rate x sample size x time x 2 • = 44100 x 16 x 3 x 60 x 2 / 8 x 1024 x 1024
    • • Stereo requires two audio streams while mono only needs one. • E.g. Calculate the file size (in Mb) of a three minute stereo audio track that has been recorded using 16 bit sound and a sampling rate of 44.1kHz. • = sample rate x sample size x time x 2 • = 44100 x 16 x 3 x 60 x 2 / 8 x 1024 x 1024