ee97c89c51
Suppose you invoke gst-launch with this invalid pipeline:
```
$ gst-launch-1.0 videotestsrc num-buffers=10 ! x264enc name=enc ! mux.sink_0 \
mpegtsmux name=mux ! fakesink
0:00:00.018631594 351169 0xb523090 ERROR GST_PIPELINE
subprojects/gstreamer/gst/parse/grammar.y:1151:gst_parse_perform_link:
could not link enc to mux
WARNING: erroneous pipeline: could not link enc to mux
```
The error message you get is not very helpful. This is a pity, because
this is where the error comes from:
```c
static GstPad *
gst_base_ts_mux_request_new_pad (GstElement * element, GstPadTemplate * templ,
const gchar * name, const GstCaps * caps)
{ // [...]
GST_ELEMENT_ERROR (element, STREAM, MUX,
("Invalid Elementary stream PID (0x%02u < 0x40)", pid), (NULL));
return NULL;
```
mpegtsmux posted an error with an explanation of why the linking failed.
However, since the error ocurred within gst_parse_launchv(), gst-launch
could not have set a bus handler, and the error message got discarded.
This patch attempts to make gst-launch more user-friendly by setting a
temporary bus handler during early bin construction to catch error
messages like this.
The errors are logged as ERROR level in the GST_PIPELINE category.
However, this is not enough, as GST_LEVEL_DEFAULT defaults to
GST_LEVEL_NONE in releases. In other words, outside of the dev
environment, GStreamer won't print ERROR logs by default.
To make sure the errors can reach users of packaged versions of
GStreamer, a new AtomicRcBox-based struct is added: reason_receiver_t.
graph_t owns a reference to reason_receiver_t and so does the temporary
bus handler.
When the temporary bus handler receives an error message, the `reason`
field of `reason_receiver_t` is filled with the error message.
Later, when SET_ERROR() is called as a consequence of the operation that
posted the error having returned failure, the reason message is
extracted and added to the GError message.
This is how the resulting error would look in the example from above:
WARNING: erroneous pipeline: could not link enc to mux --
GstMpegTsMux <mux> posted an error message: Invalid Elementary
stream PID (0x00 < 0x40)
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8417>
GStreamer 1.25.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 ask questions on the GStreamer Discourse at
https://discourse.gstreamer.org/
We track bugs, feature requests and merge requests (patches) in GitLab at
https://gitlab.freedesktop.org/gstreamer/
You can join us on our Matrix room at
https://matrix.to/#/#gstreamer:gstreamer.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/
For in-depth instructions about building GStreamer visit: getting-started.
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.