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GStreamer multimedia framework
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This commit introduces the AVTP Clock Reference Format (CRF) Synchronizer element. This element implements the AVTP CRF Listener as described in IEEE 1722-2016 Section 10. CRF is useful in synchronizing events within different systems by distributing a common clock. This is useful in a scenario where there are multiple talkers who are sending data to a single listener which is processing that data. E.g. CCTV cameras on a network sending AVTP video streams to a base station to display on the same screen. It is assumed that all the systems are already time-synchronized with each other. So, the AVTP Talker essentially adjusts the AVTP Presentation Time so it's phase-locked with the reference clock provided by the CRF stream. There are 2 different roles of systems which participate in CRF data exchange. A system can either be a CRF Talker, which samples it's own clock and generates a stream of timestamps to transmit over the network, or a CRF Listener, the system which receives the generated timestamps and recovers the media clock from the timestamps. It then adjusts it's own clock to align with recovered media clock. The timestamps generated by the talker may not be continuous and the listener might have to interpolate some timestamps to recover the media clock. The number of timestamps to interpolate is mentioned in the CRF stream AVTPDU (Refer IEEE 1722-2016 Section 10.4 for AVTPDU structure). Only CRF Listener has been implemented in this commit. The CRF Sync element will create a separate thread to listen for the CRF stream. This thread will calculate and store the average period of the recovered media clock. The pipeline thread will use this stored period along with the first timestamp of the latest CRF AVTPDU received to calculate adjustment for timestamps in the audio/video streams. In case of CRF AVTPDUs with single timestamp, two consecutive CRF AVTPDUs will be used to figure out the average period of the recovered media clock. In case of H264 streams, both AVTP timestamp and H264 timestamp will be adjusted. In the future commits, another "CRF Checker" element will be introduced which will validate the timestamps on the AVTP Listener side. Which is why a lot of code has been implemented as part of the gstcrfbase class. |
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gst | ||
gst-libs | ||
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AUTHORS | ||
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COPYING | ||
COPYING.LIB | ||
gst-plugins-bad.doap | ||
MAINTAINERS | ||
meson.build | ||
meson_options.txt | ||
NEWS | ||
README | ||
README.static-linking | ||
RELEASE | ||
REQUIREMENTS |
GStreamer 1.17.x development series WHAT IT IS ---------- This is GStreamer, a framework for streaming media. WHERE TO START -------------- We have a website at https://gstreamer.freedesktop.org Our documentation, including tutorials, API reference and FAQ can be found at https://gstreamer.freedesktop.org/documentation/ You can subscribe to our mailing lists: https://lists.freedesktop.org/mailman/listinfo/gstreamer-announce https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel We track bugs, feature requests and merge requests (patches) in GitLab at https://gitlab.freedesktop.org/gstreamer/ You can join us on IRC - #gstreamer on irc.freenode.org GStreamer 1.0 series -------------------- Starring GSTREAMER The core around which all other modules revolve. Base functionality and libraries, some essential elements, documentation, and testing. BASE A well-groomed and well-maintained collection of GStreamer plug-ins and elements, spanning the range of possible types of elements one would want to write for GStreamer. And introducing, for the first time ever, on the development screen ... THE GOOD --- "Such ingratitude. After all the times I've saved your life." A collection of plug-ins you'd want to have right next to you on the battlefield. Shooting sharp and making no mistakes, these plug-ins have it all: good looks, good code, and good licensing. Documented and dressed up in tests. If you're looking for a role model to base your own plug-in on, here it is. If you find a plot hole or a badly lip-synced line of code in them, let us know - it is a matter of honour for us to ensure Blondie doesn't look like he's been walking 100 miles through the desert without water. THE UGLY --- "When you have to shoot, shoot. Don't talk." There are times when the world needs a color between black and white. Quality code to match the good's, but two-timing, backstabbing and ready to sell your freedom down the river. These plug-ins might have a patent noose around their neck, or a lock-up license, or any other problem that makes you think twice about shipping them. We don't call them ugly because we like them less. Does a mother love her son less because he's not as pretty as the other ones ? No - she commends him on his great personality. These plug-ins are the life of the party. And we'll still step in and set them straight if you report any unacceptable behaviour - because there are two kinds of people in the world, my friend: those with a rope around their neck and the people who do the cutting. THE BAD --- "That an accusation?" No perfectly groomed moustache or any amount of fine clothing is going to cover up the truth - these plug-ins are Bad with a capital B. They look fine on the outside, and might even appear to get the job done, but at the end of the day they're a black sheep. Without a golden-haired angel to watch over them, they'll probably land in an unmarked grave at the final showdown. Don't bug us about their quality - exercise your Free Software rights, patch up the offender and send us the patch on the fastest steed you can steal from the Confederates. Because you see, in this world, there's two kinds of people, my friend: those with loaded guns and those who dig. You dig. The Lowdown ----------- --- "I've never seen so many plug-ins wasted so badly." GStreamer Plug-ins has grown so big that it's hard to separate the wheat from the chaff. Also, distributors have brought up issues about the legal status of some of the plug-ins we ship. To remedy this, we've divided the previous set of available plug-ins into four modules: - gst-plugins-base: a small and fixed set of plug-ins, covering a wide range of possible types of elements; these are continuously kept up-to-date with any core changes during the development series. - We believe distributors can safely ship these plug-ins. - People writing elements should base their code on these elements. - These elements come with examples, documentation, and regression tests. - gst-plugins-good: a set of plug-ins that we consider to have good quality code, correct functionality, our preferred license (LGPL for the plug-in code, LGPL or LGPL-compatible for the supporting library). - We believe distributors can safely ship these plug-ins. - People writing elements should base their code on these elements. - gst-plugins-ugly: a set of plug-ins that have good quality and correct functionality, but distributing them might pose problems. The license on either the plug-ins or the supporting libraries might not be how we'd like. The code might be widely known to present patent problems. - Distributors should check if they want/can ship these plug-ins. - People writing elements should base their code on these elements. - gst-plugins-bad: a set of plug-ins that aren't up to par compared to the rest. They might be close to being good quality, but they're missing something - be it a good code review, some documentation, a set of tests, a real live maintainer, or some actual wide use. If the blanks are filled in they might be upgraded to become part of either gst-plugins-good or gst-plugins-ugly, depending on the other factors. - If the plug-ins break, you can't complain - instead, you can fix the problem and send us a patch, or bribe someone into fixing them for you. - New contributors can start here for things to work on. PLATFORMS --------- - Linux is of course fully supported - FreeBSD is reported to work; other BSDs should work too; same for Solaris - MacOS works, binary 1.x packages can be built using the cerbero build tool - Windows works; binary 1.x packages can be built using the cerbero build tool - MSys/MinGW builds - Microsoft Visual Studio builds are also available and supported - Android works, binary 1.x packages can be built using the cerbero build tool - iOS works INSTALLING FROM PACKAGES ------------------------ You should always prefer installing from packages first. GStreamer is well-maintained for a number of distributions, including Fedora, Debian, Ubuntu, Mandrake, Arch Linux, Gentoo, ... Only in cases where you: - want to hack on GStreamer - want to verify that a bug has been fixed - do not have a sane distribution should you choose to build from source tarballs or git. Find more information about the various packages at https://gstreamer.freedesktop.org/download/ COMPILING FROM SOURCE TARBALLS ------------------------------ - again, make sure that you really need to install from source! If GStreamer is one of your first projects ever that you build from source, consider taking on an easier project. - you need a recent version of Meson installed, see http://mesonbuild.com/Getting-meson.html and https://gitlab.freedesktop.org/gstreamer/gst-build/blob/master/README.md - run meson build ninja -C build to build GStreamer. - if you want to install it (not required, but what you usually want to do), run ninja -C build install - try out a simple test: gst-launch-1.0 -v fakesrc num_buffers=5 ! fakesink (If you didn't install GStreamer, run `./build/tools/gst-launch-1.0`) If it outputs a bunch of messages from fakesrc and fakesink, everything is ok. If it did not work, keep in mind that you might need to adjust the PATH and/or LD_LIBRARY_PATH environment variables to make the system find GStreamer in the prefix where you installed (by default that is /usr/local). - After this, you're ready to install gst-plugins, which will provide the functionality you're probably looking for by now, so go on and read that README. COMPILING FROM GIT ------------------ You can build an uninstalled GStreamer from git for development or testing purposes without affecting your system installation. Get started with: git clone https://gitlab.freedesktop.org/gstreamer/gst-build meson build ninja -C build ninja -C build uninstalled For more information, see the `gst-build` module and its documentation: https://gitlab.freedesktop.org/gstreamer/gst-build/blob/master/README.md PLUG-IN DEPENDENCIES AND LICENSES --------------------------------- GStreamer is developed under the terms of the LGPL (see COPYING file for details). Some of our plug-ins however rely on libraries which are available under other licenses. This means that if you are distributing an application which has a non-GPL compatible license (for instance a closed-source application) with GStreamer, you have to make sure not to distribute GPL-linked plug-ins. When using GPL-linked plug-ins, GStreamer is for all practical reasons under the GPL itself. HISTORY ------- The fundamental design comes from the video pipeline at Oregon Graduate Institute, as well as some ideas from DirectMedia. It's based on plug-ins that will provide the various codec and other functionality. The interface hopefully is generic enough for various companies (ahem, Apple) to release binary codecs for Linux, until such time as they get a clue and release the source.