An audio commentary track for The Nines featuring John August along with actor Ryan Reynolds was posted in m4a and mp3 formats onto August's blog. This film had a considerably more limited release than Clerks II, featured in only 5 theaters in the U.S.
Originally inspired by a column by Roger Ebert, a small but active fan base of DVD commentary enthusiasts has sprung up since 2002 offering their own specially-recorded fan-made DVD commentaries. These tracks (usually made available in MP3 format) allow the fans to put forth their own opinions and expertise on a movie or TV series in much the same way as an on-disc commentary. These commentary tracks are played by starting a DVD player with the movie and an MP3 player with the track simultaneously. A substantial community of fan commentators exists, creating many hundreds of downloadable tracks available on the Web.
Audio content encoded in a particular audio coding format is normally encapsulated within a container format. As such, the user normally doesn't have a raw AAC file, but instead has a .m4a audio file, which is a MPEG-4 Part 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. De facto standards for adding metadata tags such as title and artist to MP3s, such as ID3, are hacks which work by appending the tags to the MP3, and then relying on the MP3 player to recognize the chunk as malformed audio coding and therefore skip it. In video files with audio, the encoded audio content is bundled with video (in a video coding format) inside a multimedia container format.
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.
Around 2002, the interest in a single, unified, streaming format and the widespread adoption of Adobe Flash prompted the development of a video streaming format through Flash, which was the format used in Flash-based players on video hosting sites. The first popular video streaming site, YouTube, was founded by Steve Chen, Chad Hurley and Jawed Karim in 2005. It initially used a Flash-based player, which played MPEG-4 AVC video and AAC audio, but now defaults to HTML5 video. Increasing consumer demand for live streaming has prompted YouTube to implement a new live streaming service to users. The company currently also offers a (secured) link returning the available connection speed of the user.
In addition to the MP4, 3GP and other container formats based on ISO base media file format for file storage, AAC audio data was first packaged in a file for the MPEG-2 standard using Audio Data Interchange Format (ADIF), consisting of a single header followed by the raw AAC audio data blocks. However, if the data is to be streamed within an MPEG-2 transport stream, a self-synchronizing format called an Audio Data Transport Stream (ADTS) is used, consisting of a series of frames, each frame having a header followed by the AAC audio data. This file and streaming-based format are defined in MPEG-2 Part 7, but are only considered informative by MPEG-4, so an MPEG-4 decoder does not need to support either format. These containers, as well as a raw AAC stream, may bear the .aac file extension. MPEG-4 Part 3 also defines its own self-synchronizing format called a Low Overhead Audio Stream (LOAS) that encapsulates not only AAC, but any MPEG-4 audio compression scheme such as TwinVQ and ALS. This format is what was defined for use in DVB transport streams when encoders use either SBR or parametric stereo AAC extensions. However, it is restricted to only a single non-multiplexed AAC stream. This format is also referred to as a Low Overhead Audio Transport Multiplex (LATM), which is just an interleaved multiple stream version of a LOAS.
It is important to distinguish between the audio coding format, the container containing the raw audio data, and an audio codec. A codec performs the encoding and decoding of the raw audio data while this encoded data is (usually) stored in a container file. Although most audio file formats support only one type of audio coding data (created with an audio coder), a multimedia container format (as Matroska or AVI) may support multiple types of audio and video data.
A client end-user can use their media player to start playing digital video or digital audio content before the entire file has been transmitted. Distinguishing delivery method from the media distributed applies specifically to telecommunications networks, as most of the delivery systems are either inherently streaming (e.g. radio, television, streaming apps) or inherently non-streaming (e.g. books, video cassettes, audio CDs). For example, in the 1930s, elevator music was among the earliest popular music available as streaming media; nowadays Internet television is a common form of streamed media. The term "streaming media" can apply to media other than video and audio, such as live closed captioning, ticker tape, and real-time text, which are all considered "streaming text".
Practical streaming media was only made possible with advances in data compression, due to the impractically high bandwidth requirements of uncompressed media. Raw digital audio encoded with pulse-code modulation (PCM) requires a bandwidth of 1.4Mbps for uncompressed CD audio, while raw digital video requires a bandwidth of 168Mbps for SD video and over 1Gbps for FHD video.