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2009-05-14 Multimedia processing

posted May 13, 2009, 4:44 PM by Unknown user   [ updated May 26, 2009, 3:24 PM by Eddie Woo ]
For further details, refer to IPT: Processing Multimedia 

1. Hardware limitations

Display hardware with a low bit depth will simply be unable to render an image with a higher bit depth than it can handle. Dithering is the process by which the bit depth of an image is reduced, by limiting the amount of colours in the image's palette. The image is processed to approximate different shades of the same colour by using one colour but using special patterns to convince humans that there are more colours being displayed than there actually are. It is used to reduce file size, but in terms of hardware limitations, it is done to prepare an image for display on hardware with a low bit depth. If a high-bit-depth image is dithered before it is attempted to be displayed on display hardware with a low bit depth, the original image can be approximated and (depending on the type of dithering used) with reasonable accuracy.
 
Storage capacity is a limitation for all information systems. Compression is a process by which more data can be stored on data storage hardware by removing superfluous data that is unlikely to be used by the human who uses the data (lossy compression e.g. JPEG, MPEG), or by using mathematical formulae to reduce the file size without reducing file quality (e.g. PNG, FLAC).

2. Creative processing

  1. [Audio used in Video] Removing unwanted sounds in an audio recording. This is done in music studios to remove accidental sounds, such as loud sound of someone dropping the microphone.
  2. [Audio used in Video] Recorded music will often have added "special effects", particularly in some genres of music such as "Techno". Such music can be used in soundtracks for films.
  3. [Image] "Retouching" photographs to remove abnormalities in the image data. This is done to remove the effects of dust, hair, dirt, etc. on the image sensor (either in a digital camera or scanner).
  4. [Image] Reduction of image noise. This is common with certain types of photography, particularly with night photography (photographs taken in poor lighting conditions are more prone to image noise due to the increased activity of the sensor arrays).
  5. [Image] Intentional reduction of the palette. Effects such as "black and white" (actually desaturation) and "sepia" reduce the palette to simulate a hardware limitation, and give the impression that an image was produced before the advent of colour image production.
  6. [Image] Colour filters. Filters applied after the capture of an image imitate the effects of an actual filter used during the capture of an image, to give the image a "warmer" or "cooler" feel.
  7. [Image] Artistic filters. Some filters in image-editing software such as Adobe Photoshop and GIMP are able to process an image to give it the appearance of a painting, drawing, or etching. Special textures, such as "sponge" and "marble", are often also used.
  8. [Image] Exposure. It is possible to adjust a photograph to compensate for over-exposure or under-exposure during image capture.
  9. [Video] The background may be intentionally blurred to give the impression of an extremely shallow depth-of-field.
  10. [Video] The frame rate can be greatly reduced or increased to give the impression of "slow motion" capture. It is also used to increase the speed of a video of a slow-motion subject, an effect often used in weather reporting, which a video camera will film the skyscape of a city to show changes in the sky.

3. Jacaranda questions 7.7

  1. Dithering and compression.
  2. Streaming.
  3. Resolution, bit depth, frame buffer, physical size, dot pitch, refresh rate.
  4. Text data cannot be approximated. There is no way to replicate a string of words such as "quick brown fox" apart from using the original data verbatim.
  5. MPEG compression works extremely well when the background remains the same (due to the use of key frames), making it ideal for interviews and the like. It also has a high compression ratio. Finally, it has been popularised due to support from popular industries and technologies such as Apple's iPod and Mac OS X operating system.
  6. ZIP format files are a file format for lossless compression. They have the ability to split a file into many small files, allowing for storage on a wider range of devices and filesystems.
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