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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...
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
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3 changed files with 126 additions and 20 deletions
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2007-01-11 Tim-Philipp Müller <tim at centricular dot net>
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* docs/random/draft-missing-plugins.txt:
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Some additions: mention new API that is supposed to be used at the
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various stages; short blob about new gst-inspect introspection
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option; mention potential future problem with plugins that have
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a dynamic list of elements (such as ladspa, pitfdll, libvisual).
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2007-01-11 Tim-Philipp Müller <tim at centricular dot net>
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* tools/gst-inspect.c:
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@ -1,6 +1,9 @@
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What to do when a plugin is missing
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===================================
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The mechanism and API described in this document requires GStreamer core and
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gst-plugins-base versions >= 0.10.12.
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We only discuss playback pipelines for now.
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A three step process:
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@ -111,6 +114,9 @@ A three step process:
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messages on the GstBus and can decide to trigger the download procedure. It
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does that as described in the following section.
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"missing-plugin" element messages can be identified using the function
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gst_is_missing_plugin_message().
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3) Plugin download stage
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@ -119,14 +125,17 @@ A three step process:
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- made a decision that additional plugins should be installed
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It will call a GStreamer utility function to convert each "missing-plugin"
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message into an identifier string describing the missing capability.
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message into an identifier string describing the missing capability. This is
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done using the function gst_missing_plugin_message_get_installer_detail().
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The application will then pass these strings to an external libgimmecodec
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to initiate the download. Error handling and progress reporting etc. will
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all be handled using libgimmecodec's API.
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The application will then pass these strings to the external libgimme-codec
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library [0] to initiate the download. Error handling and progress reporting
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etc. will all be handled using libgimmecodec's API.
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When new plugins have been installed, the application will have to initiate
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a re-scan of the GStreamer plugin registry.
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a re-scan of the GStreamer plugin registry using gst_update_registry().
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[0] http://desrt.mcmaster.ca/code/libgimme-codec/
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4) Format of the (UTF-8) string ID passed to the external installer system
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@ -174,10 +183,50 @@ A three step process:
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separated by '|' symbols and either ignore them, warn the user, or error
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out when encountering them.
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The human-readable description string will come from a new utility
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library that yet to be added to gst-plugins-base and which can then also
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be used by demuxers to find out the codec names for taglists from given
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The human-readable description string is provided by the libgstbaseutils
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library that can be found in gst-plugins-base versions >= 0.10.12 and can
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also be used by demuxers to find out the codec names for taglists from given
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caps in a unified and consistent way.
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There will also be API for applications to create these detail strings from
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a given missing-plugin message.
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Applications can create these detail strings using the function
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gst_missing_plugin_message_get_installer_detail() on a given missing-plugin
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message.
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5) Using missing-plugin messages for error reporting:
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Missing-plugin messages are also useful for error reporting purposes, either
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in the case where the application does not support libgimme-codec, or the
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external installer is not available or not able to install the required
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plugins.
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When creating error messages, applications may use the function
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gst_missing_plugin_message_get_description() to obtain a possibly translated
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description from each missing-plugin message (e.g. "Matroska demuxer" or
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"Theora video depayloader"). This can be used to report to the user exactly
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what it is that is missing.
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6) Notes for packagers
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- An easy way to introspect plugin .so files is:
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$ gst-inspect --print-plugin-auto-install-info /path/to/libgstfoo.so
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The output will be something like:
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decoder-audio/x-vorbis
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element-vorbisdec
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element-vorbisenc
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element-vorbisparse
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element-vorbistag
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encoder-audio/x-vorbis
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- when introspecting, keep in mind that there are GStreamer plugins that
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in turn load external plugins. Examples of these are pitfdll, ladspa, or
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the GStreamer libvisual plugin. Those plugins will only announce elements
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for the currently installed external plugins at the time of introspection!
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With the exception of pitfdll, this is not really relevant to the playback
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case, but may become an issue in future when applications like buzztard,
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jokosher or pitivi start requestion elements by name, for example ladspa
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effect elements or so.
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@ -1,6 +1,9 @@
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What to do when a plugin is missing
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===================================
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The mechanism and API described in this document requires GStreamer core and
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gst-plugins-base versions >= 0.10.12.
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We only discuss playback pipelines for now.
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A three step process:
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@ -111,6 +114,9 @@ A three step process:
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messages on the GstBus and can decide to trigger the download procedure. It
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does that as described in the following section.
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"missing-plugin" element messages can be identified using the function
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gst_is_missing_plugin_message().
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3) Plugin download stage
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@ -119,14 +125,17 @@ A three step process:
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- made a decision that additional plugins should be installed
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It will call a GStreamer utility function to convert each "missing-plugin"
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message into an identifier string describing the missing capability.
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message into an identifier string describing the missing capability. This is
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done using the function gst_missing_plugin_message_get_installer_detail().
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The application will then pass these strings to an external libgimmecodec
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to initiate the download. Error handling and progress reporting etc. will
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all be handled using libgimmecodec's API.
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The application will then pass these strings to the external libgimme-codec
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library [0] to initiate the download. Error handling and progress reporting
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etc. will all be handled using libgimmecodec's API.
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When new plugins have been installed, the application will have to initiate
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a re-scan of the GStreamer plugin registry.
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a re-scan of the GStreamer plugin registry using gst_update_registry().
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[0] http://desrt.mcmaster.ca/code/libgimme-codec/
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4) Format of the (UTF-8) string ID passed to the external installer system
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@ -174,10 +183,50 @@ A three step process:
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separated by '|' symbols and either ignore them, warn the user, or error
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out when encountering them.
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|
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The human-readable description string will come from a new utility
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library that yet to be added to gst-plugins-base and which can then also
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be used by demuxers to find out the codec names for taglists from given
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The human-readable description string is provided by the libgstbaseutils
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library that can be found in gst-plugins-base versions >= 0.10.12 and can
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also be used by demuxers to find out the codec names for taglists from given
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caps in a unified and consistent way.
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There will also be API for applications to create these detail strings from
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a given missing-plugin message.
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Applications can create these detail strings using the function
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gst_missing_plugin_message_get_installer_detail() on a given missing-plugin
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message.
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5) Using missing-plugin messages for error reporting:
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Missing-plugin messages are also useful for error reporting purposes, either
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in the case where the application does not support libgimme-codec, or the
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external installer is not available or not able to install the required
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plugins.
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When creating error messages, applications may use the function
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gst_missing_plugin_message_get_description() to obtain a possibly translated
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description from each missing-plugin message (e.g. "Matroska demuxer" or
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"Theora video depayloader"). This can be used to report to the user exactly
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what it is that is missing.
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6) Notes for packagers
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- An easy way to introspect plugin .so files is:
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$ gst-inspect --print-plugin-auto-install-info /path/to/libgstfoo.so
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The output will be something like:
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decoder-audio/x-vorbis
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element-vorbisdec
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element-vorbisenc
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element-vorbisparse
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element-vorbistag
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encoder-audio/x-vorbis
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- when introspecting, keep in mind that there are GStreamer plugins that
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in turn load external plugins. Examples of these are pitfdll, ladspa, or
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the GStreamer libvisual plugin. Those plugins will only announce elements
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for the currently installed external plugins at the time of introspection!
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With the exception of pitfdll, this is not really relevant to the playback
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case, but may become an issue in future when applications like buzztard,
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jokosher or pitivi start requestion elements by name, for example ladspa
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effect elements or so.
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