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docs/random/draft-missing-plugins.txt: Some additions: mention new API that is supposed to be used at the various sta...

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Original commit message from CVS:
* docs/random/draft-missing-plugins.txt:
Some additions: mention new API that is supposed to be used at the
various stages; short blob about new gst-inspect introspection
option; mention potential future problem with plugins that have
a dynamic list of elements (such as ladspa, pitfdll, libvisual).
This commit is contained in:
Tim-Philipp Müller 2007-01-11 15:03:07 +00:00
parent 26b38870f9
commit 297db8e249
3 changed files with 126 additions and 20 deletions
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8
ChangeLog
View file

@ -1,3 +1,11 @@
2007-01-11 Tim-Philipp Müller <tim at centricular dot net>
* docs/random/draft-missing-plugins.txt:
Some additions: mention new API that is supposed to be used at the
various stages; short blob about new gst-inspect introspection
option; mention potential future problem with plugins that have
a dynamic list of elements (such as ladspa, pitfdll, libvisual).
2007-01-11 Tim-Philipp Müller <tim at centricular dot net> 2007-01-11 Tim-Philipp Müller <tim at centricular dot net>
* tools/gst-inspect.c: * tools/gst-inspect.c:

69
docs/design/draft-missing-plugins.txt
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@ -1,6 +1,9 @@
What to do when a plugin is missing What to do when a plugin is missing
=================================== ===================================
The mechanism and API described in this document requires GStreamer core and
gst-plugins-base versions >= 0.10.12.
We only discuss playback pipelines for now. We only discuss playback pipelines for now.
A three step process: A three step process:
@ -111,6 +114,9 @@ A three step process:
messages on the GstBus and can decide to trigger the download procedure. It messages on the GstBus and can decide to trigger the download procedure. It
does that as described in the following section. does that as described in the following section.
"missing-plugin" element messages can be identified using the function
gst_is_missing_plugin_message().
3) Plugin download stage 3) Plugin download stage
@ -119,14 +125,17 @@ A three step process:
- made a decision that additional plugins should be installed - made a decision that additional plugins should be installed
It will call a GStreamer utility function to convert each "missing-plugin" It will call a GStreamer utility function to convert each "missing-plugin"
message into an identifier string describing the missing capability. message into an identifier string describing the missing capability. This is
done using the function gst_missing_plugin_message_get_installer_detail().
The application will then pass these strings to an external libgimmecodec The application will then pass these strings to the external libgimme-codec
to initiate the download. Error handling and progress reporting etc. will library [0] to initiate the download. Error handling and progress reporting
all be handled using libgimmecodec's API. etc. will all be handled using libgimmecodec's API.
When new plugins have been installed, the application will have to initiate When new plugins have been installed, the application will have to initiate
a re-scan of the GStreamer plugin registry. a re-scan of the GStreamer plugin registry using gst_update_registry().
[0] http://desrt.mcmaster.ca/code/libgimme-codec/
4) Format of the (UTF-8) string ID passed to the external installer system 4) Format of the (UTF-8) string ID passed to the external installer system
@ -174,10 +183,50 @@ A three step process:
separated by '|' symbols and either ignore them, warn the user, or error separated by '|' symbols and either ignore them, warn the user, or error
out when encountering them. out when encountering them.
The human-readable description string will come from a new utility The human-readable description string is provided by the libgstbaseutils
library that yet to be added to gst-plugins-base and which can then also library that can be found in gst-plugins-base versions >= 0.10.12 and can
be used by demuxers to find out the codec names for taglists from given also be used by demuxers to find out the codec names for taglists from given
caps in a unified and consistent way. caps in a unified and consistent way.
There will also be API for applications to create these detail strings from Applications can create these detail strings using the function
a given missing-plugin message. gst_missing_plugin_message_get_installer_detail() on a given missing-plugin
message.
5) Using missing-plugin messages for error reporting:
Missing-plugin messages are also useful for error reporting purposes, either
in the case where the application does not support libgimme-codec, or the
external installer is not available or not able to install the required
plugins.
When creating error messages, applications may use the function
gst_missing_plugin_message_get_description() to obtain a possibly translated
description from each missing-plugin message (e.g. "Matroska demuxer" or
"Theora video depayloader"). This can be used to report to the user exactly
what it is that is missing.
6) Notes for packagers
- An easy way to introspect plugin .so files is:
$ gst-inspect --print-plugin-auto-install-info /path/to/libgstfoo.so
The output will be something like:
decoder-audio/x-vorbis
element-vorbisdec
element-vorbisenc
element-vorbisparse
element-vorbistag
encoder-audio/x-vorbis
- when introspecting, keep in mind that there are GStreamer plugins that
in turn load external plugins. Examples of these are pitfdll, ladspa, or
the GStreamer libvisual plugin. Those plugins will only announce elements
for the currently installed external plugins at the time of introspection!
With the exception of pitfdll, this is not really relevant to the playback
case, but may become an issue in future when applications like buzztard,
jokosher or pitivi start requestion elements by name, for example ladspa
effect elements or so.

69
docs/random/draft-missing-plugins.txt
View file

@ -1,6 +1,9 @@
What to do when a plugin is missing What to do when a plugin is missing
=================================== ===================================
The mechanism and API described in this document requires GStreamer core and
gst-plugins-base versions >= 0.10.12.
We only discuss playback pipelines for now. We only discuss playback pipelines for now.
A three step process: A three step process:
@ -111,6 +114,9 @@ A three step process:
messages on the GstBus and can decide to trigger the download procedure. It messages on the GstBus and can decide to trigger the download procedure. It
does that as described in the following section. does that as described in the following section.
"missing-plugin" element messages can be identified using the function
gst_is_missing_plugin_message().
3) Plugin download stage 3) Plugin download stage
@ -119,14 +125,17 @@ A three step process:
- made a decision that additional plugins should be installed - made a decision that additional plugins should be installed
It will call a GStreamer utility function to convert each "missing-plugin" It will call a GStreamer utility function to convert each "missing-plugin"
message into an identifier string describing the missing capability. message into an identifier string describing the missing capability. This is
done using the function gst_missing_plugin_message_get_installer_detail().
The application will then pass these strings to an external libgimmecodec The application will then pass these strings to the external libgimme-codec
to initiate the download. Error handling and progress reporting etc. will library [0] to initiate the download. Error handling and progress reporting
all be handled using libgimmecodec's API. etc. will all be handled using libgimmecodec's API.
When new plugins have been installed, the application will have to initiate When new plugins have been installed, the application will have to initiate
a re-scan of the GStreamer plugin registry. a re-scan of the GStreamer plugin registry using gst_update_registry().
[0] http://desrt.mcmaster.ca/code/libgimme-codec/
4) Format of the (UTF-8) string ID passed to the external installer system 4) Format of the (UTF-8) string ID passed to the external installer system
@ -174,10 +183,50 @@ A three step process:
separated by '|' symbols and either ignore them, warn the user, or error separated by '|' symbols and either ignore them, warn the user, or error
out when encountering them. out when encountering them.
The human-readable description string will come from a new utility The human-readable description string is provided by the libgstbaseutils
library that yet to be added to gst-plugins-base and which can then also library that can be found in gst-plugins-base versions >= 0.10.12 and can
be used by demuxers to find out the codec names for taglists from given also be used by demuxers to find out the codec names for taglists from given
caps in a unified and consistent way. caps in a unified and consistent way.
There will also be API for applications to create these detail strings from Applications can create these detail strings using the function
a given missing-plugin message. gst_missing_plugin_message_get_installer_detail() on a given missing-plugin
message.
5) Using missing-plugin messages for error reporting:
Missing-plugin messages are also useful for error reporting purposes, either
in the case where the application does not support libgimme-codec, or the
external installer is not available or not able to install the required
plugins.
When creating error messages, applications may use the function
gst_missing_plugin_message_get_description() to obtain a possibly translated
description from each missing-plugin message (e.g. "Matroska demuxer" or
"Theora video depayloader"). This can be used to report to the user exactly
what it is that is missing.
6) Notes for packagers
- An easy way to introspect plugin .so files is:
$ gst-inspect --print-plugin-auto-install-info /path/to/libgstfoo.so
The output will be something like:
decoder-audio/x-vorbis
element-vorbisdec
element-vorbisenc
element-vorbisparse
element-vorbistag
encoder-audio/x-vorbis
- when introspecting, keep in mind that there are GStreamer plugins that
in turn load external plugins. Examples of these are pitfdll, ladspa, or
the GStreamer libvisual plugin. Those plugins will only announce elements
for the currently installed external plugins at the time of introspection!
With the exception of pitfdll, this is not really relevant to the playback
case, but may become an issue in future when applications like buzztard,
jokosher or pitivi start requestion elements by name, for example ladspa
effect elements or so.