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docs/random/draft-missing-plugins.txt: Update: use element message instead of adding a new message type to the core; ...

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Original commit message from CVS:
* docs/random/draft-missing-plugins.txt:
Update: use element message instead of adding a new message
type to the core; don't provide GStreamer API to initiate the
plugin download, just provide API to compose the strings needed
and let an external libgimmestuff handle the rest.
This commit is contained in:
Tim-Philipp Müller 2006-11-08 19:27:15 +00:00
parent d47c0843e4
commit 5566946241
3 changed files with 132 additions and 182 deletions
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8
ChangeLog
View file

@ -1,3 +1,11 @@
2006-11-08 Tim-Philipp Müller <tim at centricular dot net>
* docs/random/draft-missing-plugins.txt:
Update: use element message instead of adding a new message
type to the core; don't provide GStreamer API to initiate the
plugin download, just provide API to compose the strings needed
and let an external libgimmestuff handle the rest.
2006-11-08 Jan Schmidt <thaytan@mad.scientist.com> 2006-11-08 Jan Schmidt <thaytan@mad.scientist.com>
* tools/gst-inspect.c: (print_element_properties_info): * tools/gst-inspect.c: (print_element_properties_info):

153
docs/design/draft-missing-plugins.txt
View file

@ -7,16 +7,15 @@ A three step process:
1) GStreamer level 1) GStreamer level
- a new GstMessage type to report missing plugins: - elements will use a "missing-plugin" element message to report missing
plugins, with the following fields set:
GST_MESSAGE_MISSING_PLUGIN - type: (string) { "urisource", "urisink", "decoder", "encoder", "element" }
type: (string) { "urisource", "urisink", "decoder", "encoder", "element", ... (we do not distinguish between demuxer/decoders/parsers etc.)
detail: (string) { ANY } ex: "mms, "mmsh", "audio/x-mp3,rate=48000,..." - detail: (string) or (caps) depending on the type { ANY }
name: (string) { ANY } ex: "MMS protocol handler",.. ex: "mms, "mmsh", "audio/x-mp3,rate=48000,..."
- name: (string) { ANY }
=====> FIXME: really add a message type? Why not an element message? <===== ex: "MMS protocol handler",..
--- The reason for not adding a core message type is that the autopluggers
--- will post the element and the core is not intersted in this at all.
- missing uri handler - missing uri handler
@ -26,7 +25,7 @@ A three step process:
able to instantiate an element for that uri (gst_element_make_from_uri() able to instantiate an element for that uri (gst_element_make_from_uri()
returns NULL). returns NULL).
Playbin will post a GST_MESSAGE_MISSING_PLUGIN message with the type set to Playbin will post a "missing-plugin" element message with the type set to
"urisource", detail set to "mms". Optionally the friendly name can be filled "urisource", detail set to "mms". Optionally the friendly name can be filled
in as well. in as well.
@ -43,20 +42,21 @@ A three step process:
- missing demuxer - missing demuxer
Typically after running typefind on the data we determine the type of the Typically after running typefind on the data we determine the type of the
file. If there is no plugin found for the type, a GST_MESSAGE_PLUGIN_MISSING file. If there is no plugin found for the type, a "missing-plugin" element
is posted by decodebin with the following fields: Type set to "decoder", message is posted by decodebin with the following fields: Type set to
detail set to the caps for witch no plugin was found. Optionally the friendly "decoder", detail set to the caps for witch no plugin was found. Optionally
name can be filled in as well. the friendly name can be filled in as well.
- missing decoder - missing decoder
The demuxer will dynamically create new pads with specific caps while it The demuxer will dynamically create new pads with specific caps while it
figures out the contents of the container format. Decodebin tries to find the figures out the contents of the container format. Decodebin tries to find the
decoders for these formats in the registry. If there is no decoder found, a decoders for these formats in the registry. If there is no decoder found, a
MISSING_PLUGIN is posted by decodebin with the following fields: Type set to "missing-plugin" element message is posted by decodebin with the following
"decoder", detail set to the caps for which no plugin was found. Optionally fields: Type set to "decoder", detail set to the caps for which no plugin
the friendly name can be filled in as well. There is no distinction made was found. Optionally the friendly name can be filled in as well. There is
between the missing demuxer and decoder at the application level. no distinction made between the missing demuxer and decoder at the
application level.
- missing element - missing element
@ -64,10 +64,10 @@ A three step process:
their decoding pipeline. These elements are typically colorspace, sample rate, their decoding pipeline. These elements are typically colorspace, sample rate,
audio sinks,... Their presence on the system is required for the functionality audio sinks,... Their presence on the system is required for the functionality
of decodebin. It is typically a package dependency error if they are not of decodebin. It is typically a package dependency error if they are not
present but in case of a corrupted system the following PLUGIN_MISSING message present but in case of a corrupted system the following "missing-plugin"
will be emitted: type set to "element", detail set to the element factory name element message will be emitted: type set to "element", detail set to the
and the friendly name optionally set to a description of the element's element factory name and the friendly name optionally set to a description
functionality in the decoding pipeline. of the element's functionality in the decoding pipeline.
Except for reporting the missing plugins, no further policy is enforced at the Except for reporting the missing plugins, no further policy is enforced at the
GStreamer level. It is up to the application to decide whether a missing GStreamer level. It is up to the application to decide whether a missing
@ -76,13 +76,13 @@ A three step process:
2) application level 2) application level
The application's job is to listen for the MISSING_PLUGIN messages and to The application's job is to listen for the "missing-plugin" element messages
decide on a policy to handle them. Following cases exist: and to decide on a policy to handle them. Following cases exist:
- partially missing plugins - partially missing plugins
The application will be able to complete a state change to PAUSED but there The application will be able to complete a state change to PAUSED but there
will be a MISSING_PLUGIN message on the GstBus. will be a "missing-plugin" element message on the GstBus.
This means that it will be possible to play back part of the media file but not This means that it will be possible to play back part of the media file but not
all of it. all of it.
@ -104,82 +104,53 @@ A three step process:
playback stopped (before it could reach PAUSED). This happens because none of playback stopped (before it could reach PAUSED). This happens because none of
the streams is connected to a decoder. the streams is connected to a decoder.
The application can then see that there are a set of MISSING_PLUGIN messages on The application can then see that there are a set of "missing-plugin" element
the GstBus and can decide to trigger the download procedure. It does that messages on the GstBus and can decide to trigger the download procedure. It
by calling gst_install_missing_plugins() which is documented above, passing does that as described in the following section.
the MISSING_PLUGIN messages collected.
3) Plugin download stage 3) Plugin download stage
In addition, a thin callback API will be added to GStreamer to initiate At this point the application has
plugin download and receive feedback about whether the plugin download - collected one or more "missing-plugin" element messages
succeeded (in full or partially) or failed. - made a decision that additional plugins should be installed
struct GstMissingPluginHandler { It will call a GStreamer utility function to convert each "missing-plugin"
/* This function must be blocking; the function is implemented by an message into an identifier string describing the missing capability.
* external library (chosen by the application) */
gboolean (*install_plugins) (const gchar ** missing_ids, GError ** error, gpointer handler_data);
/*< private >*/ The application will then pass these strings to an external libgimmecodec
gpointer padding[GST_PADDING]; to initiate the download. Error handling and progress reporting etc. will
}; all be handled using libgimmecodec's API.
typedef void (GstMissingPluginInstallResultFunc *) (const GError * error, When new plugins have been installed, the application will have to initiate
gpointer user_data); a re-scan of the GStreamer plugin registry.
/* The GstMissingPluginHandler struct is provided by some helper library
* which implements the IPC details; this function does not block and will
* return immediately; the result_callback function will be called when the
* IPC implementation has finished (this might happen from the context of
* another thread, it is the responsibility of the application to take care
* of locking or marshalling the result back into the main thread in a
* thread-safe manner */
gboolean gst_install_missing_plugins (const GstMissingPluginHandler * handler,
gpointer handler_data,
GList * messages,
GstMissingPluginInstallResultFunc result_callback,
gpointer result_callback_data,
GError ** error);
=====> FIXME: progress function? (+ make API better) <=========
gst_install_missing_plugins() takes a GList of PLUGIN_MISSING messages and
a GstMissingPluginHandler structure which specifies the implementation of
the IPC mechanism. It will transform each PLUGIN_MISSING message into an
ID string that among other things identifies the type of missing capability.
Mapping this ID to packages and downloading and installing packages is the
responsibility of the external IPC system.
The gst_install_missing_plugins() callback will initiate a re-scan
of the available plugins before calling the result_callback with a
positive result.
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
The string is made up of several fields, separated by '|' characters.
The fields are:
- plugin system identifier, ie. gstreamer.net The string is made up of several fields, separated by '|' characters.
- plugin system version, e.g. 0.10 The fields are:
- application identifier, e.g. totem
- human-readable localised description of the required component,
e.g. "Vorbis audio decoder"
- identifier string for the required component, e.g.
- urisource-$(PROTOCOL_REQUIRED)
e.g. urisource-http or urisource-mms
- element-$(ELEMENT_REQUIRED),
e.g. element-ffmpegcolorspace
- decoder-$(CAPS_REQUIRED)
e.g. decoder-audio/x-vorbis or decoder-application/ogg
- encoder-$(CAPS_REQUIRED)
e.g. encoder-audio/x-vorbis
An entire ID string might then look like this, for example: - plugin system identifier, ie. gstreamer.net
- plugin system version, e.g. 0.10
- application identifier, e.g. totem
- human-readable localised description of the required component,
e.g. "Vorbis audio decoder"
- identifier string for the required component, e.g.
- urisource-$(PROTOCOL_REQUIRED)
e.g. urisource-http or urisource-mms
- element-$(ELEMENT_REQUIRED),
e.g. element-ffmpegcolorspace
- decoder-$(CAPS_REQUIRED)
e.g. decoder-audio/x-vorbis or decoder-application/ogg
- encoder-$(CAPS_REQUIRED)
e.g. encoder-audio/x-vorbis
gstreamer.net|0.10|totem|Vorbis audio decoder|decoder-audio/x-vorbis An entire ID string might then look like this, for example:
The human-readable description string will come from a new utility gstreamer.net|0.10|totem|Vorbis audio decoder|decoder-audio/x-vorbis
library that yet to be added to gst-plugins-base and which can then also
be used by demuxers to find out the codec names for taglists from given The human-readable description string will come from a new utility
caps in a unified and consistent way. library that yet to be added to gst-plugins-base and which can then also
be used by demuxers to find out the codec names for taglists from given
caps in a unified and consistent way.

153
docs/random/draft-missing-plugins.txt
View file

@ -7,16 +7,15 @@ A three step process:
1) GStreamer level 1) GStreamer level
- a new GstMessage type to report missing plugins: - elements will use a "missing-plugin" element message to report missing
plugins, with the following fields set:
GST_MESSAGE_MISSING_PLUGIN - type: (string) { "urisource", "urisink", "decoder", "encoder", "element" }
type: (string) { "urisource", "urisink", "decoder", "encoder", "element", ... (we do not distinguish between demuxer/decoders/parsers etc.)
detail: (string) { ANY } ex: "mms, "mmsh", "audio/x-mp3,rate=48000,..." - detail: (string) or (caps) depending on the type { ANY }
name: (string) { ANY } ex: "MMS protocol handler",.. ex: "mms, "mmsh", "audio/x-mp3,rate=48000,..."
- name: (string) { ANY }
=====> FIXME: really add a message type? Why not an element message? <===== ex: "MMS protocol handler",..
--- The reason for not adding a core message type is that the autopluggers
--- will post the element and the core is not intersted in this at all.
- missing uri handler - missing uri handler
@ -26,7 +25,7 @@ A three step process:
able to instantiate an element for that uri (gst_element_make_from_uri() able to instantiate an element for that uri (gst_element_make_from_uri()
returns NULL). returns NULL).
Playbin will post a GST_MESSAGE_MISSING_PLUGIN message with the type set to Playbin will post a "missing-plugin" element message with the type set to
"urisource", detail set to "mms". Optionally the friendly name can be filled "urisource", detail set to "mms". Optionally the friendly name can be filled
in as well. in as well.
@ -43,20 +42,21 @@ A three step process:
- missing demuxer - missing demuxer
Typically after running typefind on the data we determine the type of the Typically after running typefind on the data we determine the type of the
file. If there is no plugin found for the type, a GST_MESSAGE_PLUGIN_MISSING file. If there is no plugin found for the type, a "missing-plugin" element
is posted by decodebin with the following fields: Type set to "decoder", message is posted by decodebin with the following fields: Type set to
detail set to the caps for witch no plugin was found. Optionally the friendly "decoder", detail set to the caps for witch no plugin was found. Optionally
name can be filled in as well. the friendly name can be filled in as well.
- missing decoder - missing decoder
The demuxer will dynamically create new pads with specific caps while it The demuxer will dynamically create new pads with specific caps while it
figures out the contents of the container format. Decodebin tries to find the figures out the contents of the container format. Decodebin tries to find the
decoders for these formats in the registry. If there is no decoder found, a decoders for these formats in the registry. If there is no decoder found, a
MISSING_PLUGIN is posted by decodebin with the following fields: Type set to "missing-plugin" element message is posted by decodebin with the following
"decoder", detail set to the caps for which no plugin was found. Optionally fields: Type set to "decoder", detail set to the caps for which no plugin
the friendly name can be filled in as well. There is no distinction made was found. Optionally the friendly name can be filled in as well. There is
between the missing demuxer and decoder at the application level. no distinction made between the missing demuxer and decoder at the
application level.
- missing element - missing element
@ -64,10 +64,10 @@ A three step process:
their decoding pipeline. These elements are typically colorspace, sample rate, their decoding pipeline. These elements are typically colorspace, sample rate,
audio sinks,... Their presence on the system is required for the functionality audio sinks,... Their presence on the system is required for the functionality
of decodebin. It is typically a package dependency error if they are not of decodebin. It is typically a package dependency error if they are not
present but in case of a corrupted system the following PLUGIN_MISSING message present but in case of a corrupted system the following "missing-plugin"
will be emitted: type set to "element", detail set to the element factory name element message will be emitted: type set to "element", detail set to the
and the friendly name optionally set to a description of the element's element factory name and the friendly name optionally set to a description
functionality in the decoding pipeline. of the element's functionality in the decoding pipeline.
Except for reporting the missing plugins, no further policy is enforced at the Except for reporting the missing plugins, no further policy is enforced at the
GStreamer level. It is up to the application to decide whether a missing GStreamer level. It is up to the application to decide whether a missing
@ -76,13 +76,13 @@ A three step process:
2) application level 2) application level
The application's job is to listen for the MISSING_PLUGIN messages and to The application's job is to listen for the "missing-plugin" element messages
decide on a policy to handle them. Following cases exist: and to decide on a policy to handle them. Following cases exist:
- partially missing plugins - partially missing plugins
The application will be able to complete a state change to PAUSED but there The application will be able to complete a state change to PAUSED but there
will be a MISSING_PLUGIN message on the GstBus. will be a "missing-plugin" element message on the GstBus.
This means that it will be possible to play back part of the media file but not This means that it will be possible to play back part of the media file but not
all of it. all of it.
@ -104,82 +104,53 @@ A three step process:
playback stopped (before it could reach PAUSED). This happens because none of playback stopped (before it could reach PAUSED). This happens because none of
the streams is connected to a decoder. the streams is connected to a decoder.
The application can then see that there are a set of MISSING_PLUGIN messages on The application can then see that there are a set of "missing-plugin" element
the GstBus and can decide to trigger the download procedure. It does that messages on the GstBus and can decide to trigger the download procedure. It
by calling gst_install_missing_plugins() which is documented above, passing does that as described in the following section.
the MISSING_PLUGIN messages collected.
3) Plugin download stage 3) Plugin download stage
In addition, a thin callback API will be added to GStreamer to initiate At this point the application has
plugin download and receive feedback about whether the plugin download - collected one or more "missing-plugin" element messages
succeeded (in full or partially) or failed. - made a decision that additional plugins should be installed
struct GstMissingPluginHandler { It will call a GStreamer utility function to convert each "missing-plugin"
/* This function must be blocking; the function is implemented by an message into an identifier string describing the missing capability.
* external library (chosen by the application) */
gboolean (*install_plugins) (const gchar ** missing_ids, GError ** error, gpointer handler_data);
/*< private >*/ The application will then pass these strings to an external libgimmecodec
gpointer padding[GST_PADDING]; to initiate the download. Error handling and progress reporting etc. will
}; all be handled using libgimmecodec's API.
typedef void (GstMissingPluginInstallResultFunc *) (const GError * error, When new plugins have been installed, the application will have to initiate
gpointer user_data); a re-scan of the GStreamer plugin registry.
/* The GstMissingPluginHandler struct is provided by some helper library
* which implements the IPC details; this function does not block and will
* return immediately; the result_callback function will be called when the
* IPC implementation has finished (this might happen from the context of
* another thread, it is the responsibility of the application to take care
* of locking or marshalling the result back into the main thread in a
* thread-safe manner */
gboolean gst_install_missing_plugins (const GstMissingPluginHandler * handler,
gpointer handler_data,
GList * messages,
GstMissingPluginInstallResultFunc result_callback,
gpointer result_callback_data,
GError ** error);
=====> FIXME: progress function? (+ make API better) <=========
gst_install_missing_plugins() takes a GList of PLUGIN_MISSING messages and
a GstMissingPluginHandler structure which specifies the implementation of
the IPC mechanism. It will transform each PLUGIN_MISSING message into an
ID string that among other things identifies the type of missing capability.
Mapping this ID to packages and downloading and installing packages is the
responsibility of the external IPC system.
The gst_install_missing_plugins() callback will initiate a re-scan
of the available plugins before calling the result_callback with a
positive result.
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
The string is made up of several fields, separated by '|' characters.
The fields are:
- plugin system identifier, ie. gstreamer.net The string is made up of several fields, separated by '|' characters.
- plugin system version, e.g. 0.10 The fields are:
- application identifier, e.g. totem
- human-readable localised description of the required component,
e.g. "Vorbis audio decoder"
- identifier string for the required component, e.g.
- urisource-$(PROTOCOL_REQUIRED)
e.g. urisource-http or urisource-mms
- element-$(ELEMENT_REQUIRED),
e.g. element-ffmpegcolorspace
- decoder-$(CAPS_REQUIRED)
e.g. decoder-audio/x-vorbis or decoder-application/ogg
- encoder-$(CAPS_REQUIRED)
e.g. encoder-audio/x-vorbis
An entire ID string might then look like this, for example: - plugin system identifier, ie. gstreamer.net
- plugin system version, e.g. 0.10
- application identifier, e.g. totem
- human-readable localised description of the required component,
e.g. "Vorbis audio decoder"
- identifier string for the required component, e.g.
- urisource-$(PROTOCOL_REQUIRED)
e.g. urisource-http or urisource-mms
- element-$(ELEMENT_REQUIRED),
e.g. element-ffmpegcolorspace
- decoder-$(CAPS_REQUIRED)
e.g. decoder-audio/x-vorbis or decoder-application/ogg
- encoder-$(CAPS_REQUIRED)
e.g. encoder-audio/x-vorbis
gstreamer.net|0.10|totem|Vorbis audio decoder|decoder-audio/x-vorbis An entire ID string might then look like this, for example:
The human-readable description string will come from a new utility gstreamer.net|0.10|totem|Vorbis audio decoder|decoder-audio/x-vorbis
library that yet to be added to gst-plugins-base and which can then also
be used by demuxers to find out the codec names for taglists from given The human-readable description string will come from a new utility
caps in a unified and consistent way. library that yet to be added to gst-plugins-base and which can then also
be used by demuxers to find out the codec names for taglists from given
caps in a unified and consistent way.