Audio

1. Audio

2. Audio • Audio can be imported into authoring packages and is used to enhance interactions and animations

3. Audio – info from Flash Help • WAV (Windows only) • AIFF (Macintosh only) • mp3 (Windows or Macintosh) • If you have QuickTime 4 or later installed on your system, you can import these additional sound file formats: • AIFF (Windows or Macintosh) • Sound Designer II (Macintosh only) • Sound Only QuickTime Movies (Windows or Macintosh) • Sun AU (Windows or Macintosh) • System 7 Sounds (Macintosh only) • WAV (Windows or Macintosh)

4. Audio - info from Flash Help • Flash stores sounds in the library along with bitmaps and symbols. You need only one copy of a sound file to use that sound multiple ways in your document. • Sounds can use large amounts of disk space and RAM. However, mp3 sound data is compressed and smaller than WAV or AIFF sound data. Generally, when using WAV or AIFF files, it’s best to use 16-22 kHz mono sounds (stereo uses twice as much data as mono), but Flash can import either 8- or 16-bit sounds at sample rates of 11, 22, or 44 kHz. Sounds recorded in formats that are not multiples of 11 kHz (such as 8, 32, or 96 kHz) are resampled when imported into Flash. Flash can convert sounds to lower sample rates on export. • If you want to add effects to sounds in Flash, it’s best to import 16-bit sounds. If you have limited RAM, keep your sound clips short or work with 8-bit sounds instead of 16‑bit sounds.

5. Audio – MP3 • Digital Audio • Analogue sound is picked up by a microphone and converted to a voltage that changes constantly over time. • There is no missing information because there is always a voltage recorded. Results in a continuous, unbroken waveform

6. Audio – MP3 • Analogue to digital conversion • The analogue signal is sampled • At particular time intervals, the voltage is measured and converted to a value and this value is recorded • The sampling is done by an analogue-to-digital converter ADC Values are only recorded for the points sampled. All other information (between these points) is lost Obviously, lower sample rates produce lower quality reproductions of the sounds

7. Audio – MP3 • Analogue to digital conversion • Bits… • For every sampled value recorded there is also a choice to be made about how much information to record for that sample • Digital values are stored as bits which are binary units (have to be binary as the processor deals with on or off at it’s base level) • 8 bits is 28 • 16 bits is 216 • Etc • So , higher bits allow for more information to be saved. • But if we save more information it is slower to process it and file sizes are higher • However, if we save less information we can loose sound quality – some lower voltages may have numbers too large to store in 8 bits and so will be recorded as 0

8. Audio – MP3 • Analogue to digital conversion • Common sample rate for CD quality sound is • 44,100 times per second • 44,100Hz • 44.1KHz • Common bit depth for CD quality sound is 16 bits • 16 bits allows for just under the normal human hearing range to be recorded

9. Audio – MP3 • Once converted to a digital format, audio may be further manipulated to take up even less space as a file • This is done by compression • Compression applies a mathematical formula to the data to make file sizes smaller • As images, have 2 sorts of compression • Lossless and lossy • No data loss, some data loss.

10. Audio – MP3 • Mp3 is a lossy compression • MPEG-1 Audio Layer 3 • Motion Picture Expert Group • - now an international standard • Very complex algorithm removes pieces of data that research shows is beyond the ability of most people to distinguish between • A technique known as perceptual coding • MP3 compression set depending on bit rate – a measure of how many bits of data can be processed per second • A cd quality track compressed to mp3 will be approx 10% of the cd track size at a 128kbs setting

11. Audio – MP3 • In order to hear the audio file: • it needs to be decompressed • and reconverted to a continuous voltage value (DAC – digital-to-analogue conversion)…. • That can be fed to the speakers out put device • Computers therefore require codecs to produce and read the various audio files • Codecsc= compressors and decompressors

12. Can test the sound and see Whether it’s stereo or mono Audio • Imported sounds go into library – have a speaker icon for identification

13. Audio • MP3s are the lightest in terms of file size – can compress audio when publishing your Flash movie – look at this later • Quickest and easiest way to get a sound to play is to drag it on to the stage and stretch it out on the timeline • example

14. Effects can be added here Audio • Once on the timeline, can add effects through the properties panel

15. Audio • Effects • None – removes any effects previously added • Left Channel – sound only plays in left channel • Right Channel - sound only plays in right channel • Fade Left to Right/Fade Right to Left - fades the sound from one channel to the other. • Fade In gradually increases the sound volume • FadeOut gradually decreases the sound volume • Custom lets you manipulate sound using the Edit Envelope.

16. Can create custom points on the sound envelope and manipulate these Can reset time in and out markers Audio • Edit Envelope example

17. Audio • Sync – this option in the properties panel controls the timing of the sound • Event • Start • Stop • Stream • Event sounds • These are synchronised to a particular event • They start playing as soon as the event is triggered and continue to play all the way through to the end • They are not stopped by another event • button example

18. Audio • Start sounds • These behave as event sounds but if a sound is already playing, a new instance of the sound will not start - button example • Stop sounds • This stops the sound chosen • Stream Sounds • This is not the same as streaming sound • stream sounds are used for movies published for the web • The audio is synchronized to play with an animation • If there are problems syncing the animation then animation frames are dropped so the sound can play in its entirety. - example

19. Set sounds to repeat or to loop here (don’t use this for stream sounds as it increases file size massively) Audio • Repeating and looping • You can also set sounds to loop eternally or to repeat a set number of times example

20. Audio • Audio • Placing sounds directly on the timeline is still fairly common for animations • Better practice for other uses to dynamically add the sound – use code to load and play sounds • Have more control over the sound • Makes file sizes smaller • Applications run faster • More on how to do this later….