Analysis of music in video games - part 2

L3 Extended Diploma in Games Design

Unit 73: Sound for Computer Games

Aims:

P2 Understand the methods and principles of sound design and production

Research and explain when you would use the following sounds format and why?

Sound file formats

Uncompressed

WAV

This stands for Waveform Audio File, .WAV being its file extension. It was introduced in 1991 by Microsoft and IBM for use in the Windows 3.1 OS. The WAV file can digitize sounds 100% faithfully to the original source as it is a lossless format. “Lossless” means that the file format does not compromise audio quality even when it holds compressed data.

Many people have heard WAV files when using a PC without even realizing that is what they are. The various chimes and alert noises a computer system makes are courtesy of embedded WAV files - before that they were just beeps and clicks, noises that were recognizably electronic.

WAV files work by taking an audio signal and then converting it to binary data. In order to do this, a device called an analogue to digital converter (AD) takes snapshot ‘slices’ thousands of times per second. As an illustration of this, CD quality audio records at 44.1kHz, meaning it records at 44,100 slices per second.

Despite being an older file format, The WAV file has several major advantages over other formats:

• It is an accurate, lossless format
  This means that the recording is as close to the original source recording as is possible
• It is a simple format
  
  This means that due to the simplicity of the file it can be opened and edited by the majority of software on the market. From freeware to professional applications, a WAV file can be interpreted, edited and re saved with a minimum of fuss.
• It is a format that has a huge recording rate
  WAV files can record a huge dynamic range, from small whispering noises to booming sounds and everything in between. As an illustration ‘home’ audio interfaces offer up to 192kHz - kHz being the number representing the range of audio available.

There are however, also drawbacks:

• They are large file sizes
  A stereo, CD quality recording (44.1khz, 16-bit), works out at 10.09 MB per minute. Moving up to 48kHz 24-bit stereo (which will improve both the frequency range and the available dynamic range) will increase file size to 16.48 MB per minute.
  
  
• The large file sizes make streaming extremely impractical for tablets and portable devices.

AIFF

Apple derived its own version of the WAV file format in 1988:  AIFF. Essentially, AIFFs are the apple equivalent of WAVs.

AU

These are files produced by the program 'Audacity', an open source sound recording and editing application. These are a special format that only Audacity can open. As well as the actual audio data, they can contain project information and settings.

SMP

An ".smp" file may be one of several different types of audio file. For example, it could be a SampleVision audio sample file. This 16-bit audio file was originally used by Turtle Beach SampleVision; you can open it with Adobe Auction, Sound Forge Pro or Awave Studio. It could also be a sample file for AdLib Gold, a PC sound card released in 1992; Scream Tracker, a mid-1990s music editing program; or Swell. Reason, a music recording and production program, uses the ".smp" extension for sampler instrument patches.

VOC

Files that contain the .voc file extension are most commonly associated with digital recording hardware devices. These can include Dictaphones and other types of portable handheld recorder produced by Creative Labs.

VOC files can contain audio clips, music files, instrument sounds and sound effects that are used with the associated hardware device. The VOC file format is a compressed file format, allowing for a reduction in the size of the audio file.

Lossy compression

MP3

MP3 is a shortened name for MPEG-2 audio layer III. The format was developed by the Moving Picture Experts Group, hence the name. Unlike WAV files, MP3's are a lossy format. This means that encoding audio to MP3 will reduce the sound quality as well as the file size. The file format is clever because it manipulates the frequencies that the human ear can audibly detect.

MP3's can encode data in such a way that they can work out what will be impossible to detect. The encoding process eliminates any audio data that is deemed as superfluous or unnecessary, creating smaller files.

MP3's also know that if there are sounds that are loud, they will be masked by certain quieter sounds. Therefore the format is able to eliminate these ‘hidden’ levels of noise.

Finally, MP3's exploit the fact that ear will hear some frequencies better than others. This process is termed the ‘threshold of audibility’.

The advantages of MP3 files are:

• Small file format
  Because files are so small, they can be easily distributed over the Internet, and huge libraries stored on computers or handheld devices. Because of this, they have become the consumer standard for purchasing music.

• Compresses files with little perceivable difference to the overall sound quality.

• Easy to convert a WAV or CD to MP3 with free software

The disadvantages of MP3 files are:

• To compress the file, audio quality is sacrificed
  Although very clever, odd audio quirks can appear called 'artifacts'. These are usually heard at higher frequencies.

• This audio inaccuracy means that MP3s are not suitable for pro audio work.

RA

This refers to the file extension "Real Audio". It was introduced by RealNetworks in 1995, the latest version of these files is Real Audio 10. Real Audio is used in particular for streaming audio due to its ability to work with low internet bandwidths. Because of this .ra files are commonly used by internet radio stations.

One of the disadvantages of this format is the fact the Real Audio Player by RealNetworks is required to play .ra files. To get around this, some people download the free Real Alternative Player or JetAudio Player to listen to these files. However, a free additional plug in is still required.

That is the reason many users convert .rax / .ra files to other more popular audio formats like .mp3, .aav, .wav, .wma that can be played universally. A good audio converter will keep the highest quality of audio.

VOX

VOX file formats store digitized human speech and cannot replicate music.In practice they are used for voice recording and compression. 


Audio sampling
How can resolution and bit depth constrain file size?
Bit depth refers to the clarity of the audio and how much sound and ambient noise is picked up on the recording. For example a high rate of bit depth could pick up breathing, any small noises involuntarily made by the person and background talking as well as environmental sounds. The downside of this is that a much greater overall file size is created,

Resolution refers to the crispness of the recording - whether it is muddy or clean sounding. Again, an emphasis on clean, crisp audio recording will create a much larger file.



Explain what the following words mean:
Sample rate
During recording, the more samples that are taken of a sound per second, the more accurate the digital representation will be.

Mono
Mono refers to a single speaker playback of a sound. The sound can be quite flat and monotone, lacking depth and presence.

Stereo
Stereo refers to dual speaker playback of a sound. This adds greater depth and sound quality, creating a greater presence of sound and atmosphere in the room.

Surround
Surround refers to multiple speakers placed around the listener to a create a realistic sense of overall immersion in the audio. Sound can be digitally manipulated to travel from speaker to speaker to give the listener a sense of movement.