# GPAC Project on Advanced Content

GPAC Project on Advanced Content (GPAC, a recursive acronym) is an open-source multimedia framework focused on modularity and standards compliance. GPAC was created as an implementation of the MPEG-4 Systems standard written in ANSI C and later extended in Streaming Media. GPAC provides tools to process, inspect, package, stream, media playback and interact with media content. Such content can be any combination of audio, video, subtitles, metadata, encrypted media, rendering and ECMAScript.
GPAC provides three sets of tools based on a core library called libgpac:
* A multimedia packager, MP4Box
* A general pipeline engine, gpac, introduced in version 1.0 (2019)
* A media player.
GPAC is cross-platform. It is written in (almost 100% ANSI) C for portability reasons, attempting to keep the memory footprint as low as possible. It is currently running under Windows, Linux, MacOS X, iOS, Android, and many other systems.
GPAC is best known for its wide MP4/ISOBMFF capabilities and is popular among video enthusiasts, academic researchers, standardization bodies, and professional broadcasters.

## History and standards

GPAC was founded in New York City in 1999 as a company called AviPix. In 2003, it became open-source, with the initial goal of developing from scratch, in ANSI C, clean software compliant with the MPEG-4 Systems architecture standard, as a small and flexible alternative to the MPEG-4 reference software.
In parallel, as MPEG-4 was intended to compete with Macromedia Flash, GPAC evolved to support other standards such as X3D, W3C SVG Tiny 1.2, and OMA/3GPP/ISMA and eventually MPEG-DASH. The MPEG-DASH feature can be used to reconstruct .mp4 files from videos streamed and cached in this format (e.g., YouTube). Various research projects used or use GPAC.
In 2019 the GPAC team explained the code has undergone a massive re-architecture called Filters with release 0.9 while release 0.8 is the last release of the legacy architecture with an extended 18-months support. The front-end applications remain unchanged, making the transition seamless. The underlying filters build a dynamic modular dataflow pipeline.
In 2020 GPAC 1.0 was released. The Website was split into a wiki documentation, a doxygen API documentation, a buildbot and GitHub actions, a testbot with a high coverage. The new gpac application has been used as a FFmpeg on steroids offering additional speed, features, ease of use.
Since 2013, GPAC Licensing has offered business support and closed-source licenses. In 2022 Netflix announced using GPAC for their worldwide content operations including the Netflix service, studio content, and merchandising material.

## Multimedia content features
### Packaging

GPAC features encoders and multiplexers, publishing and content distribution tools for MP4 files and many tools for scene descriptions (BIFS/VRML/X3D converters, SWF/BIFS, SVG/BIFS, etc.). MP4Box provides all these tools in a single command-line application. Current supported features are:
* MP4/3GP Conversion from MP3, AVI, MPEG-2 TS, MPEG-PS, AAC, H263, H264, H265, H266, H266, AMR, and many others,
* 3GPP DIMS Packaging from SVG tiny 1.2 files,
* File layout: fragmentation or interleaving, and cleaning,
* File hinting for RTP/RTSP and QTSS/DSS servers (MPEG-4/ISMA/3GP/ 3GP2 files),
* File splitting by size or time, extraction from file and file concatenation,
* XML information dumping for MP4 and RTP hint tracks,
* Media Track extractions,
* ISMA E&A encryption and decryption,
* 3GPP timed text tools (SUB/SRT/TTXT/TeXML), VobSub import/export,
* BIFS codec and scene conversion between MP4, BT and XMT-A,
* LASeR codec and scene conversion between MP4, SAF, SVG and XSR (XML LASeR),
* XML scene statistics for BIFS scene (BT, XMT-A and MP4),
* Conversion to and from BT, XMT-A, WRL, X3D and X3DV with support for gzip.
* A syntax that ensures that simple operations, i.e. concatenating 3 files into one new one, are not simple.

### Playing

GPAC supports many protocols and standards, among which:
* BIFS scenes (2D, 3D and mixed 2D/3D scenes),
* VRML 2.0 (VRML97) scenes (without GEO or NURBS extensions),
* X3D scenes (not complete) in X3D (XML) and X3DV (VRML) formats,
* SVG Tiny 1.2 scenes (including packaged in 3GP DIMS files),
* LASeR and SAF (partial) support,
* Progressive loading/rendering of SVG, X3D and XMT files,
* HTTP reading of all scene descriptions,
* GZIP supported for all textual formats of MPEG4/X3D/VRML/SVG,
* MP4 and 3GPP file reading (local & http),
* MP3 and AAC files (local & http) and HTTP streaming (ShoutCast/ICEcast radios),
* Most common media codecs for image, audio and video,
* Most common media containers,
* 3GPP Timed Text / MPEG-4 Streaming Text,
* MPEG-2 TS demultiplexer (local/UDP/RTP) with DVB support (Linux only),
* Streaming support through RTP/RTCP (unicast and multicast) and RTSP/SDP,
* Plugins for Mozilla (osmozilla, Win32 and Linux) and Internet Explorer (GPAX, Win32 and PPC 2003).

### Streaming

As of version 0.4.5, GPAC has some experimental server-side and streaming tools:
* MP4/3GP file RTP streamer (unicast and multicast),
* RTP streamer with service timeslicing (DVB-H) simulation,
* MPEG-2 TS broadcaster using MP4/3GP files or RTP streams as inputs,
* BIFS RTP broadcaster tool performing live encoding and RandomAccessPoints generation.

## Contributors

The project is hosted at Télécom_Paris, a leading French engineering school. Current main contributors of GPAC are:
* Jean Le Feuvre
* Romain Bouqueau
* Aurélien David
Other (current or past) contributors are:
* Cyril Concolato
* Jérôme Gorin
* Pierre Souchay
* Jean-Claude Moissinac
* Jean-Claude Dufourd
* Benoit Pellan
* Philippe de Cuetos.
Additionally, GPAC is used at Télécom Paris for pedagogical purposes. Students regularly participate in the development of the project.