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Common File Formats (Audio)

Applied IT (Year 11) - Application Skills (U1)

Jeckmen Wu

Types of Audio Files

Moving Pictures Experts Group (.mp3)

Short for MPEG-1 Audio Layer 3, MP3 is a lossy compressed audio container that is widely compatible and ideal for web-based use. To reduce file size for storage and sharing, the compression algorithm will dissect the audio into individual frames and then use psychoacoustics (i.e. how humans perceive sound) to determine which pieces of data in each frame can be discarded. This typically includes information that do not lie within the audible frequency range, or are redundant (e.g. less noticeable sounds that can be masked by a more dominant sound with a higher volume or frequency). There will of course be a trade-off between file size and sound quality, but the drop-off isn’t usually significantly noticeable or problematic for the casual everyday listener.  

Waveform Audio File Format (.wav)

Uses a process called Linear Pulse Code Modulation (LCPM) or digitisation/sampling to convert analogue audio signals into digital binary code for storage (this process is reversed by the playback device to produce sound). LCPM involves sampling the audio for a standard of 44,100 times per second (44.1 kHz), with each sample recording the amplitude, bit depth (usually 16 or 24-bit), and channel information (i.e. left, right or mono) at that exact point in time. The sample rate will typically rise to 48, 88.2 or 96 kHz per second for professional applications. Unsurprisingly, the uncompressed file size will be a lot larger than MP3s, but with the ability to capture and retain the subtle details in the original audio.

Windows Media Audio File (.wma)

A lossy audio file format developed by Microsoft. The main distinguishing feature from the other two formats is WMA’s proprietary technology which offers support for digital rights management (DRM). DRM protection allows musicians to apply licences and copyright to restrict the use of their audio files. However, WMA is not as widely compatible as MP3s beyond Microsoft products.

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