Windows Media Audio (WMA) is a series of audio codecs and their corresponding audio coding formats developed by Microsoft. It is a proprietary technology that forms part of the Windows Media framework. WMA consists of four distinct codecs. The original WMA codec, known simply as WMA, was conceived as a competitor to the popular MP3 and RealAudio codecs. WMA Pro, a newer and more advanced codec, supports multichannel and high-resolution audio. A lossless codec, WMA Lossless, compresses audio data without loss of audio fidelity. WMA Voice, targeted at voice content, applies compression using a range of low bit rates. Microsoft has also developed a digital container format called Advanced Systems Format to store audio encoded by WMA.
RealMedia is a proprietary multimedia container format created by RealNetworks with the filename extension .rm. RealMedia is generally used in conjunction with RealVideo and RealAudio, while also being used for streaming content over the Internet. Typically these streams are in CBR, but a container for VBR streams named RMVB has been developed.
RealAudio, also spelled Real Audio, is a proprietary audio format developed by RealNetworks and first released in April 1995. It uses a variety of audio codecs, ranging from low-bitrate formats that can be used over dialup modems, to high-fidelity formats for music. It can be used as a streaming audio format, that is played at the same time as it is downloaded.
Speex is an audio compression codec specifically tuned for the reproduction of human speech and also a free software speech codec that may be used on voice over IP applications and podcasts. It is based on the code excited linear prediction speech coding algorithm. Its creators claim Speex to be free of any patent restrictions and it is licensed under the revised (3-clause) BSD license. It may be used with the Ogg container format or directly transmitted over UDP/RTP. It may also be used with the FLV container format.
FFmpeg is a free and open-source software project consisting of a suite of libraries and programs for handling video, audio, and other multimedia files and streams. At its core is the command-line ffmpeg tool itself, designed for processing video and audio files. It is widely used for format transcoding, basic editing, video scaling, video post-production effects, and standards compliance.
Advanced Audio Coding (AAC) is an audio coding standard for lossy digital audio compression. It was designed to be the successor of the MP3 format and generally achieves higher sound quality than MP3 at the same bit rate.
RealVideo, or also spelled as Real Video, is a suite of proprietary video compression formats developed by RealNetworks — the specific format changes with the version. It was first released in 1997 and as of 2008 was at version 10. RealVideo is supported on many platforms, including Windows, Mac, Linux, Solaris, and several mobile phones.
On2 TrueMotion VP3 is a (royalty-free) lossy video compression format and video codec. It is an incarnation of the TrueMotion video codec, a series of video codecs developed by On2 Technologies.
VLC media player is a free and open-source, portable, cross-platform media player software and streaming media server developed by the VideoLAN project. VLC is available for desktop operating systems and mobile platforms, such as Android, iOS and iPadOS. VLC is also available on digital distribution platforms such as Apple's App Store, Google Play, and Microsoft Store.
RealPlayer, formerly RealAudio Player, RealOne Player and RealPlayer G2, is a cross-platform media player app, developed by RealNetworks. The media player is compatible with numerous container file formats of the multimedia realm, including MP3, MP4, QuickTime File Format, Windows Media format, and the proprietary RealAudio and RealVideo formats. RealPlayer is also available for other operating systems; Linux, Unix, Palm OS, Windows Mobile, and Symbian versions have been released.
Extended Adaptive Multi-Rate – Wideband (AMR-WB+) is an audio codec that extends AMR-WB. It adds support for stereo signals and higher sampling rates. Another main improvement is the use of transform coding additionally to ACELP. This greatly improves the generic audio coding. Automatic switching between transform coding and ACELP provides both good speech and audio quality with moderate bit rates.
3GP is a multimedia container format defined by the Third Generation Partnership Project (3GPP) for 3G UMTS multimedia services. It is used on 3G mobile phones but can also be played on some 2G and 4G phones.
FAAC is a software project which includes the AAC encoder FAAC and decoder FAAD2. It supports MPEG-2 AAC as well as MPEG-4 AAC. It supports several MPEG-4 Audio object types, file formats, multichannel and gapless encoding/decoding and MP4 metadata tags. The encoder and decoder is compatible with standard-compliant audio applications using one or more of these object types and facilities. It also supports Digital Radio Mondiale.
Flash Video is a container file format used to deliver digital video content over the Internet using Adobe Flash Player version 6 and newer. Flash Video content may also be embedded within SWF files. There are two different Flash Video file formats: FLV and F4V. The audio and video data within FLV files are encoded in the same way as SWF files. The F4V file format is based on the ISO base media file format, starting with Flash Player 9 update 3. Both formats are supported in Adobe Flash Player and developed by Adobe Systems. FLV was originally developed by Macromedia. In the early 2000s, Flash Video was the de facto standard for web-based streaming video. Users include Hulu, VEVO, Yahoo! Video, metacafe, Reuters.com, and many other news providers.
The following tables compare general and technical information for a variety of audio coding formats.
HTTP Live Streaming is an HTTP-based adaptive bitrate streaming communications protocol developed by Apple Inc. and released in 2009. Support for the protocol is widespread in media players, web browsers, mobile devices, and streaming media servers. As of 2022, an annual video industry survey has consistently found it to be the most popular streaming format.
The Helix Universal Media Server was a product developed by RealNetworks and originates from the first streaming media server originally developed by Progressive Networks in 1994. It supported a variety of streaming media delivery transports including MPEG-DASH RTMP (flash), RTSP (standard), HTTP Live Streaming (HLS), Microsoft Silverlight and HTTP Progressive Download enabling mobile phone OS and PC OS media client delivery.
Dynamic Adaptive Streaming over HTTP (DASH), also known as MPEG-DASH, is an adaptive bitrate streaming technique that enables high quality streaming of media content over the Internet delivered from conventional HTTP web servers. Similar to Apple's HTTP Live Streaming (HLS) solution, MPEG-DASH works by breaking the content into a sequence of small segments, which are served over HTTP. An early HTTP web server based streaming system called SProxy was developed and deployed in the Hewlett Packard Laboratories in 2006. It showed how to use HTTP range requests to break the content into small segments. SProxy shows the effectiveness of segment based streaming, gaining best Internet penetration due to the wide deployment of firewalls, and reducing the unnecessary traffic transmission if a user chooses to terminate the streaming session earlier before reaching the end. Each segment contains a short interval of playback time of content that is potentially many hours in duration, such as a movie or the live broadcast of a sport event. The content is made available at a variety of different bit rates, i.e., alternative segments encoded at different bit rates covering aligned short intervals of playback time. While the content is being played back by an MPEG-DASH client, the client uses a bit rate adaptation (ABR) algorithm to automatically select the segment with the highest bit rate possible that can be downloaded in time for playback without causing stalls or re-buffering events in the playback. The current MPEG-DASH reference client dash.js offers both buffer-based (BOLA) and hybrid (DYNAMIC) bit rate adaptation algorithms. Thus, an MPEG-DASH client can seamlessly adapt to changing network conditions and provide high quality playback with few stalls or re-buffering events.
HTML audio is a subject of the HTML specification, incorporating audio input, playback, and synthesis, all in the browser.
