Category Archives: 3. Multimedia

Image compression

A big thanks to Colin for putting me on to this YouTube channel. As we saw in today’s lesson computer images (digital) can be very large. In order to save space when we save them we must compress them. We can either do this in a lossless fashion or in a lossy fashion. With lossless you can always get back to the original without any corruption this is not possible in lossy compression.

[kml_flashembed movie="http://www.youtube.com/v/Lto-ajuqW3w" width="425" height="344" allowfullscreen="true" fvars="fs=1" /]

Multimedia NAB 2 – Graphics Task

Navigate to the Computing->Higher->Multimedia->NAB2 folder on the pupil share.

  • Using Photoshop CS3 merge the hot air balloon and landscape to make a new graphic.
  • Create an SVG in notepad using the Blank.svg file. It should be an image of a Red Circle inside a blue square.

You are allowed to use the Internet and this blog to find assistance in completing this task. Both files should be saved in your file area before being printed, black and white is fine.

Video & Sound Calculations

  1. Calculate the uncompressed file size of a 2.5 minute audio clip recorded in stereo at 44.1 kHz using 65536 different sounds. Show all your working. (4)
  2. A commercial has been recorded to promote a new show. The commercial; is an uncompressed, 30 second stereo file, sampled at 40KHz and in 16-bit sound. Calculate the file size for the commercial. Give your answer in appropriate units. (3)
  3. A video is captured at 12 frames per second with 2 million pixels in 24-bit colour and lasts for 5 minutes. Calculate the storage capacity required to store the video. Give your answer in appropriate units (ignore sound and compression in your answer). (3)
  4. A video clip was recorded using 15 frames per second in 24 bit colour depth with 600 x 800 pixels. The clip lasts for 2 minutes. Calculate the file size of the video clip. Ignore sound and compression in your calculation. Show all working and express your answer in appropriate units. (3)

Answers after the jump

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Implications of the use of multimedia technology

It’s been a busy couple of days.

When we think about communications we can break them down to wired and wireless. The trend in communication is toward faster and more secure connections. This increase in bandwidth can be achieved with compression and improved speed due to falling costs.

The trend is storage solutions is for faster access of larger storage capacity. This is driven by the rapid uptake of multimedia applications that make use of video. Take a look at the progression

  • CD-ROM – can store an music album of about 72 minutes without compression
  • DVD-ROM – can store an entire SD movie
  • Blu-Ray – can store an entire 3D HD movie (3d requires twice the storage)

Processors are becoming  more power efficient. This allows the the processors to be run at faster clock speeds and for each processor to have multiple cores. This allows for more media to be displayed and processed at the same time.

Display technology have moved toward greater pixel density and higher resolutions on a flat display. This coupled with cheaper 3D displays has allowed virtual 3D to move from the cinema screen to the the LCD screen. In the future volumetric displays will allow the projection of images that will allow the user to look at objects from all sides.

Links after the jump

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Synthesised sound data

Sampled audio files can take up a large amount of storage space. It is possible to digitally create sound and therefore music digitally, this is often known as FM Synthesis. A standard called MIDI was created to allow Musical Instruments to be connected together using a Digital Interface. These MIDI packets contain data that describes which instrument to play and the details of the notes to be played. Here is an online editor to try.

[kml_flashembed movie="http://www.youtube.com/v/IJqTtGA0Bkc" width="425" height="344" allowfullscreen="true" fvars="fs=1" /]

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