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YouTube originally offered videos at only one quality level, displayed at a resolution of 320×240 pixels using the Sorenson Spark codec (a variant of H.263), [29] [30] with mono MP3 audio. [31] In June 2007, YouTube added an option to watch videos in 3GP format on mobile phones. [ 32 ]
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The ISO base media file format (ISOBMFF) is a container file format that defines a general structure for files that contain time-based multimedia data such as video and audio. [ 3 ] [ 4 ] It is standardized in ISO / IEC 14496-12, a.k.a. MPEG-4 Part 12, and was formerly also published as ISO/IEC 15444-12, a.k.a. JPEG 2000 Part 12.
The MP4 file format defined some extensions over the ISO Base Media File Format to support MPEG-4 visual/audio codecs and various MPEG-4 Systems features such as object descriptors and scene descriptions. Some of these extensions are also used by other formats based on the ISO base media file format (e.g., 3GP). [1]
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 audio 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.
A file format for the Free Lossless Audio Codec, an open-source lossless compression codec. .gsm: Designed for telephony use in Europe, GSM is used to store telephone voice messages and conversations. With a bitrate of 13 kbit/s, GSM files can compress and encode audio at telephone quality. [7] Note that WAV files can also be encoded with the ...
Typically, the replay gain and peak level values are then stored as metadata in the audio file. ReplayGain-capable audio players use the replay gain metadata to automatically attenuate or amplify the signal on a per-track or per-album basis such that tracks or albums play at a similar loudness level.
[11] [12] It was designed to greatly reduce the amount of data required to represent audio, yet still sound like a faithful reproduction of the original uncompressed audio to most listeners; for example, compared to CD-quality digital audio, MP3 compression can commonly achieve a 75–95% reduction in size, depending on the bit rate. [13]