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Cropping is a tool for selecting sections of a file without damaging the rest of the file. Cropping a sound file allows a short section of music to be selected for play; a video can be cropped to display only one short scene.

Rendering is of particular importance when converting wireframe models to realistically display a final product. It is also used to improve the quality of sound or video.

Sampling allows sound files to be manipulated. Analogue sound can vary over an infinite range. (A dial is an analogue controller as it can be turned to control sound over many levels.) Converting an analogue signal into a digit audio file requires an ADC (analogue to digital converter). These are usually found on a sound card.

Put simply, sampling takes a variable wave and records a wave high of 1 and a wave low of 0. To get the variation in frequency and amplitude, sampling uses a sample size (bit rate) and a sample rate. Sample size is the number of bits used to represent each sample: the more bits, the more faithfully variations in volume can be represented. Bit rate measures the number of bits transmitted per second. Common bit rates are:

• 8 bit – 8 bit sound is a poor audio quality but good for voice recording • 16 bit – standard CD audio (256 times better than 8 bit) • 24 bit – professional quality audio. Sample rate is the number of times per second a wave is analysed and recorded (sampled). The sampling rate (samples per second or hertz) determines the fidelity (trueness) with which different frequencies can be reproduced. High frequencies are lost if the sampling rate is not high enough. The rate needs to be set to twice as fast as the highest frequency on the sound track sampled. Common sample rates used in digital audio include:

• 44100 or 44 kHz – used for most CDs and • 32000 or 32 kHz – used for broadcasts.

This means that a CD has better quality sound than a broadcast. Audio sequences assist the sound card to capture and edit sound using a sound meter to view the level of the wave as it is input in order to avoid the top levels of the waves being clipped off and distorting the sound. Editing tools can be used to remove pops, spikes and static, or to clip the sound to size. The sound file can then be stored on media such as a digital audio tape, CD audio, mini disk or DVD audio.

Morphing ( Image 1) is the organisation of graphical and audio data so that, across a series of frames, one image or sound changes to another by blending into the next one. Morphing allows for smooth

transitions. Morphing images may be done by tweening. Tweening basically begins with one framed image

Digital Media�

Bede Polding College Information Software and Technology

Name: Date:

DMW6A Use of Common Manipulation Techniques

Morphing

The organisation of graphical and audio data so that, across a series of frames, one

image or sound changes to another

by blending into the next one.

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Image 1. Example of a morphed image of a Woman into a Lion https://ccrma.stanford.edu/~jacobliu/368Report/

�in an animation or video and ends with a totally different image, or the same image in a different position. A program allows you to create the first and last frames of an animation and then generates all the frames in between. When morphing is not involved, tweening changes the original image to give the illusion of movement. Tweening involving morphing uses a different image for the start and end frames. The program creates the in between frames. Two advantages of tweening are the time saved during production of the file, and the reduction in the amount of storage needed for the file compared to methods that create individual frames.

Download a digital copy of this worksheet at http://goo.gl/g7nP51

Digital Media�

Bede Polding College Information Software and Technology

1. Describe how sample rate is different from sample size.

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2. Explain the process of morphing a sound. (You will be assessed on your paragraph and sentence writing skills with this question)

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3. Give reasons for using tweening during animation

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