Audio and Image Files

Lossy Compression

Lossy compression takes advantage of the human limitations by removing invisible information that we will not notice that much. The image will just look a tad blurrier.

Lossy Files

• A lossy compression method is one where compressing data and then decompressing it retrieves data that may well be different from the original, but is close enough to be useful in some way. Lossy compression is most commonly used to compress multimedia data (audio, video, still images), especially in applications such as streaming media. By contrast, lossless compression is required for text and data files, such as bank records, text articles, etc.

• Lossy compression formats suffer from generation loss: repeatedly compressing and decompressing the file will cause it to progressively lose quality. This is in contrast with lossless data compression.

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Examples of Lossy video files include MNG, MPEG-1, MPEG-2, MPEG-4 and VC-1.

Examples Of Lossy Video Files

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Lossless what is it?Lossless data compression is a class of data compression

algorithms that allows the exact original data to be reconstructed from the compressed data.

The term lossless is in contrast to lossy data compression, which only allows an approximation of the original data to be reconstructed, in exchange for better compression rates.

Lossless data compression is used in many applications. For example, it is used in the popular ZIP file format. It is also often used as a component within lossy data.

Lossless Compression

This reduces the file size but does not reduce the quality of the image.

The compression is not close to the extent of the lossy compression.

When is it used?Lossless compression is used when it is important that the

original and the decompressed data be identical, or when no assumption can be made on whether certain deviation is uncritical.

Typical examples are executable programs and source code. Some image file formats, like PNG, GIF, WMV and MP4 use only lossless compression, while others like TIFF and MNG may use either lossless or lossy methods.

It can also be used as

Audio: Realplayer

Graphics: GIF

Video: CorePNG

It is important to distinguish between a file format and a codec. A codec performs the encoding and decoding of the raw audio data while the data itself is stored in a file with a specific audio file format. Though most audio file formats support only one audio codec, a file format may support

multiple codec's, as AVI does.

There are three major groups of audio file formats:Uncompressed audio formats, such as WAV, AIFF and AU;

formats with lossless compression, such as FLAC, Monkey’s Audio (filename extension APE), WavPack

(filename extension WV), Shorten, Tom's lossless Audio Kompressor (TAK), TTA, ATRAC Advanced Lossless, Apple

Lossless and lossless Window Media Audio (WMA). formats with lossy compression, such as MP3, Vorbis,

Musepack, ATRAC, lossy Windows Media Audio( WMA) and AAC.

What is BWF (Broadcast wave format)

Is an extension of the popular Microsoft WAVE audio format and is the recording format of most file-based non-linear digital recorders used for motion picture and television production.

The purpose of this file format is the addition of metadata to facilitate the seamless exchange of sound data between different computer platforms and applications. It specifies the format of metadata, allowing audio processing elements to identify themselves, document their activities, and permit synchronization with other recordings. This metadata is stored as extension chunks in a standard digital audio WAV file.

WAVWAVWAVWAVWaveform audio formatWaveform audio format

Standard audio file container format used Standard audio file container format used mainly in Windows PCs mainly in Windows PCs

The WAV format is limited to files that are The WAV format is limited to files that are less than 4 GB in size less than 4 GB in size

Uncompressed WAV files are quite large in Uncompressed WAV files are quite large in size, so, as file sharing over the Internet has size, so, as file sharing over the Internet has

become popular, the WAV format has become popular, the WAV format has declined in popularity. declined in popularity.

WMA(Windows Media Audio)

Windows Media Audio (WMA) is an audio data compression technology developed by Microsoft. The name can be used to refer to its audio file format or its audio codecs. It is a proprietary technology that forms part of the Windows Media framework. WMA consists of four distinct codecs.

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Lossy (you do lose some of the file quality)Designed to reduce the amount of data required to represent audio recording.MP3 stands for MPEG. Audio layer 3

MPEG-4

• MPEG-4 is a lossy video file. It was introduced in 1998 and stands for Moving Picture Experts Group, and combines the

features of MPEG-1 and MPEG-2.

JPEG JPEG stands for ‘Joint Photographic

Experts Group’ this file is a lossy format, nearly every digital camera can save images in the JPEG format, which supports 8 bits per colour (red, green, blue) for a 24-bit total, producing relatively small files. When not too great, the compression does not noticeably detract from the image's quality, but JPEG files suffer generational degradation when repeatedly edited and saved

GIF GIF stands for ‘Graphics Interchange Format’

is limited to an 8-bit palette, or 256 colours. This makes the GIF format suitable for storing graphics with relatively few colours such as simple diagrams, shapes, logos and cartoon style images. The GIF format supports animation and is still widely used to provide image animation effects. It also uses a lossless compression that is more effective when large areas have a single colour, and ineffective for detailed images or dithered images .

PNG PNG stands for Portable Network Graphics

file format was created as the free, open-source successor to the GIF. The PNG file format supports truecolor (16 million colours) while the GIF supports only 256 colours. The PNG file excels when the image has large, uniformly coloured areas. The lossless PNG format is best suited for editing pictures, and the lossy formats, like JPG, are best for the final distribution of photographic images, because JPG files are smaller than PNG files

BMP

The BMP file format (Windows bitmap) handles graphics files within the Microsft Windows OS. Typically, BMP files are uncompressed, hence they are large; the advantage is their simplicity, wide acceptance, and use in Windows programs

These are the rest of the image formats

Lossless (Does not remove information) reduces bandwidth and storage requirements

without sacrificing the integrity of the audio source

Non proprietary + Open source

46% compression rate