Archive for February, 2008

The Prelim.

February 27, 2008

examsinprogress.jpg

Sorry there have not been many posts for a while, but then there have not been many Higher Computing lessons for a while. The prelim was yesterday morning and is now in the process of being marked.

If you took advantage of the chat room support the night before you would have realised that calculation questions would be important (along with a lot of other topics!).

If you want extra practice try this question:

A stereo audio file has been recorded at CD quality and is 3 minutes 12 seconds long. It is to be stored on a solid state flash drive. How much space will it take up in an uncompressed format?

Answers as comments please…..

RIFF files

February 7, 2008

Yet another acronym! Just one more to go along with PAM, PCM, ADPCM, MP3…..

This one (Resource Interchange File Format orRIFF) is a container file i.e. contains more than one type of data.

It is was created by Microsoft and IBM (according to Wikipedia anyway) as a multimedia content file. The header (first section) of the file determines what kind of data is in it. The picture below explains it better than I can.

riff-diagram.jpg

Here is the slide from todays lesson:

riff.jpg

Digitised Sound

February 4, 2008

This lesson I played some live radiohead (whose latest album was free to download) to try and get you thinking about capturing sound for digital use. For Higher Computing you need to be able to describe (in a 3 mark way) how sound is captured (microphone), changes into voltage, and is then digitised (by the ADC). You also need to have a good understanding of the terms sampling depth (how many bits are used to measure the analogue signal) and sampling frequency (how often the analogue signal is measured per second).

digitsed-sound.jpgsampling-depth-frequency.jpg