Audio File Format
I want to read more about audio file formats.
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- Audio Coding Format
- An audio coding format (or sometimes audio compression format) is a content representation format for storage or transmission of digital audio (such as digital television, digital radio, and in audio and video files). Examples of audio coding formats include MP3, AAC, Vorbis, FLAC, and Opus.
- Some audio coding formats are documented by a detailed technical specification document known as an audio coding specification. Some such specifications are known as audio coding standard. Audio content encoded in a particular audio coding format is normally encapsulated with a container format. The user doesn't normally have a raw AAC file, but instead has a
.mp4audio file, which is aMPEG-4Part 14 container containing AAC-encoded audio. The container also contains metadata such as title and other tags, and perhaps an index for fast seeking. A notable exception is MP3 files, which are raw audio coding without a container format. An audio coding format does not dictate all algorithms used by a codec implementing the format. - A lossless audio coding format reduces the total data needed to represent a sound but can be de-coded to its original, uncompressed form. A lossy coding format additionally reduces the bit resolution of the sound on top of compression, which results in far less data at the cost of irretrievably lost information.
- Some audio coding formats are documented by a detailed technical specification document known as an audio coding specification. Some such specifications are known as audio coding standard. Audio content encoded in a particular audio coding format is normally encapsulated with a container format. The user doesn't normally have a raw AAC file, but instead has a
- Audio Codec
- An audio codec, or audio decoder is a device or computer program capable of encoding or decoding a digital data stream (a codec) that encodes or decodes audio. In software, an audio codec is a computer program implementing an algorithm that compresses and decompresses digital audio data according to a given audio file or streaming media audio coding format.
- The objective of the algorithm is to represent the high-fidelity audio signal with a minimum number of bits while retaining quality. This can reduce the storage space and the bandwidth required for transmission of the stored audio file.
- In hardware, audio codec refers to a single device that encodes analog audio as digital signals and decodes digital back into analog. It contains both an analog-to-digital converter (ADC) and digital-to-analog converter (DAC) running off the same clock signal.
- Container Format
- A container format (informally, sometimes called a wrapper) or metafile is a file format that allows multiple data streams to be embedded into a single file, usually along with metadata for identifying and further detailing those streams. Notable examples include archive files (such as the ZIP format) and formats used for multimedia playback (such as MP4).
- Although containers may identify how data or metadata is encoded, they do not actually provide instructions about how to decode that data. A program that can open a container must also use an appropriate codec to decode its contents.
Notes
An audio file format is a file format for storing digital audio data on a computer system. The bit layout of the audio data (excluding metadata) is called the audio coding format and can be uncompressed, or compressed to reduce the file size, often using lossy compression. The data can be a raw bitstream in an audio coding format, but it is usually embedded in a container format or an audio data format with defined storage layer.
Although most audio file formats support inly one type of audio coding data (created with an audio coder), a multimedia container format may support multiple types of audio and video data.
Three major groups of audio file formats:
- Uncompressed:
WAV,AIFF,AU, orPCM - Formats with lossless compression, such as
FLAC,.ape,.wv,MPEG-4 - Formats with lossy compression, such as Opus, MP3, Vorbis, AAC
A lossless compressed audio format stores data in less space without losing any information. The original, uncompressed data can be recreated from the compressed version.
Uncompressed audio formats encode both sound and silence with the same number of bits per unit of time. In lossless compression, this is not the case: silence would take up almost no space at all.
Lossy audio format enables even greater reductions in file size by removing some of the audio information and simplifying the data. This results in a reduction in audio quality, but a variety of techniques are used, mainly by exploiting psychoacoustics, to remove the parts of the sound that have the least effect on perceived quality, and to minimize the amount of audible noise added during the process.