playbin2

playbin2 — Autoplug and play media from an uri

Synopsis

struct              GstPlayBin2;
enum                GstPlayFlags;

Object Hierarchy

  GObject
   +----GstObject
         +----GstElement
               +----GstBin
                     +----GstPipeline
                           +----GstPlayBin2

Implemented Interfaces

GstPlayBin2 implements GstChildProxy and GstStreamVolume.

Properties

  "audio-sink"               GstElement*           : Read / Write
  "connection-speed"         guint                 : Read / Write
  "current-audio"            gint                  : Read / Write
  "current-text"             gint                  : Read / Write
  "current-video"            gint                  : Read / Write
  "flags"                    GstPlayFlags          : Read / Write
  "frame"                    GstBuffer*            : Read
  "n-audio"                  gint                  : Read
  "n-text"                   gint                  : Read
  "n-video"                  gint                  : Read
  "source"                   GstElement*           : Read
  "subtitle-encoding"        gchar*                : Read / Write
  "subtitle-font-desc"       gchar*                : Write
  "suburi"                   gchar*                : Read / Write
  "uri"                      gchar*                : Read / Write
  "video-sink"               GstElement*           : Read / Write
  "vis-plugin"               GstElement*           : Read / Write
  "volume"                   gdouble               : Read / Write
  "mute"                     gboolean              : Read / Write
  "buffer-duration"          gint64                : Read / Write
  "buffer-size"              gint                  : Read / Write
  "text-sink"                GstElement*           : Read / Write
  "subpic-sink"              GstElement*           : Read / Write
  "av-offset"                gint64                : Read / Write
  "ring-buffer-max-size"     guint64               : Read / Write

Signals

  "about-to-finish"                                : Run Last
  "audio-changed"                                  : Run Last
  "get-audio-tags"                                 : Action
  "get-text-tags"                                  : Action
  "get-video-tags"                                 : Action
  "text-changed"                                   : Run Last
  "video-changed"                                  : Run Last
  "convert-frame"                                  : Action
  "get-audio-pad"                                  : Action
  "get-text-pad"                                   : Action
  "get-video-pad"                                  : Action
  "audio-tags-changed"                             : Run Last
  "text-tags-changed"                              : Run Last
  "video-tags-changed"                             : Run Last
  "source-setup"                                   : Run Last

Description

Playbin2 provides a stand-alone everything-in-one abstraction for an audio and/or video player.

playbin2 is considered stable now. It is the prefered playback API now, and replaces the old playbin element, which is no longer supported.

It can handle both audio and video files and features

  • automatic file type recognition and based on that automatic selection and usage of the right audio/video/subtitle demuxers/decoders
  • visualisations for audio files
  • subtitle support for video files. Subtitles can be store in external files.
  • stream selection between different video/audio/subtitles streams
  • meta info (tag) extraction
  • easy access to the last video frame
  • buffering when playing streams over a network
  • volume control with mute option

Usage

A playbin2 element can be created just like any other element using gst_element_factory_make(). The file/URI to play should be set via the "uri" property. This must be an absolute URI, relative file paths are not allowed. Example URIs are file:///home/joe/movie.avi or http://www.joedoe.com/foo.ogg

Playbin is a GstPipeline. It will notify the application of everything that's happening (errors, end of stream, tags found, state changes, etc.) by posting messages on its GstBus. The application needs to watch the bus.

Playback can be initiated by setting the element to PLAYING state using gst_element_set_state(). Note that the state change will take place in the background in a separate thread, when the function returns playback is probably not happening yet and any errors might not have occured yet. Applications using playbin should ideally be written to deal with things completely asynchroneous.

When playback has finished (an EOS message has been received on the bus) or an error has occured (an ERROR message has been received on the bus) or the user wants to play a different track, playbin should be set back to READY or NULL state, then the "uri" property should be set to the new location and then playbin be set to PLAYING state again.

Seeking can be done using gst_element_seek_simple() or gst_element_seek() on the playbin element. Again, the seek will not be executed instantaneously, but will be done in a background thread. When the seek call returns the seek will most likely still be in process. An application may wait for the seek to finish (or fail) using gst_element_get_state() with -1 as the timeout, but this will block the user interface and is not recommended at all.

Applications may query the current position and duration of the stream via gst_element_query_position() and gst_element_query_duration() and setting the format passed to GST_FORMAT_TIME. If the query was successful, the duration or position will have been returned in units of nanoseconds.


Advanced Usage: specifying the audio and video sink

By default, if no audio sink or video sink has been specified via the "audio-sink" or "video-sink" property, playbin will use the autoaudiosink and autovideosink elements to find the first-best available output method. This should work in most cases, but is not always desirable. Often either the user or application might want to specify more explicitly what to use for audio and video output.

If the application wants more control over how audio or video should be output, it may create the audio/video sink elements itself (for example using gst_element_factory_make()) and provide them to playbin using the "audio-sink" or "video-sink" property.

GNOME-based applications, for example, will usually want to create gconfaudiosink and gconfvideosink elements and make playbin use those, so that output happens to whatever the user has configured in the GNOME Multimedia System Selector configuration dialog.

The sink elements do not necessarily need to be ready-made sinks. It is possible to create container elements that look like a sink to playbin, but in reality contain a number of custom elements linked together. This can be achieved by creating a GstBin and putting elements in there and linking them, and then creating a sink GstGhostPad for the bin and pointing it to the sink pad of the first element within the bin. This can be used for a number of purposes, for example to force output to a particular format or to modify or observe the data before it is output.

It is also possible to 'suppress' audio and/or video output by using 'fakesink' elements (or capture it from there using the fakesink element's "handoff" signal, which, nota bene, is fired from the streaming thread!).


Retrieving Tags and Other Meta Data

Most of the common meta data (artist, title, etc.) can be retrieved by watching for TAG messages on the pipeline's bus (see above).

Other more specific meta information like width/height/framerate of video streams or samplerate/number of channels of audio streams can be obtained from the negotiated caps on the sink pads of the sinks.


Buffering

Playbin handles buffering automatically for the most part, but applications need to handle parts of the buffering process as well. Whenever playbin is buffering, it will post BUFFERING messages on the bus with a percentage value that shows the progress of the buffering process. Applications need to set playbin to PLAYING or PAUSED state in response to these messages. They may also want to convey the buffering progress to the user in some way. Here is how to extract the percentage information from the message (requires GStreamer >= 0.10.11):
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switch (GST_MESSAGE_TYPE (msg)) {
  case GST_MESSAGE_BUFFERING: {
    gint percent = 0;
    gst_message_parse_buffering (msg, &percent);
    g_print ("Buffering (%%u percent done)", percent);
    break;
  }
  ...
}
Note that applications should keep/set the pipeline in the PAUSED state when a BUFFERING message is received with a buffer percent value < 100 and set the pipeline back to PLAYING state when a BUFFERING message with a value of 100 percent is received (if PLAYING is the desired state, that is).


Embedding the video window in your application

By default, playbin (or rather the video sinks used) will create their own window. Applications will usually want to force output to a window of their own, however. This can be done using the GstXOverlay interface, which most video sinks implement. See the documentation there for more details.


Specifying which CD/DVD device to use

The device to use for CDs/DVDs needs to be set on the source element playbin creates before it is opened. The only way to do this at the moment is to connect to playbin's "notify::source" signal, which will be emitted by playbin when it has created the source element for a particular URI. In the signal callback you can check if the source element has a "device" property and set it appropriately. In future ways might be added to specify the device as part of the URI, but at the time of writing this is not possible yet.


Handling redirects

Some elements may post 'redirect' messages on the bus to tell the application to open another location. These are element messages containing a structure named 'redirect' along with a 'new-location' field of string type. The new location may be a relative or an absolute URI. Examples for such redirects can be found in many quicktime movie trailers.


Examples

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gst-launch -v playbin uri=file:///path/to/somefile.avi
This will play back the given AVI video file, given that the video and audio decoders required to decode the content are installed. Since no special audio sink or video sink is supplied (not possible via gst-launch), playbin will try to find a suitable audio and video sink automatically using the autoaudiosink and autovideosink elements.
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gst-launch -v playbin uri=cdda://4
This will play back track 4 on an audio CD in your disc drive (assuming the drive is detected automatically by the plugin).
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gst-launch -v playbin uri=dvd://1
This will play back title 1 of a DVD in your disc drive (assuming the drive is detected automatically by the plugin).

Synopsis

Element Information

plugin

playback

author

Wim Taymans <wim.taymans@gmail.com>

class

Generic/Bin/Player

Element Pads

Details

struct GstPlayBin2

struct GstPlayBin2;

playbin element structure


enum GstPlayFlags

typedef enum {
  GST_PLAY_FLAG_VIDEO         = (1 << 0),
  GST_PLAY_FLAG_AUDIO         = (1 << 1),
  GST_PLAY_FLAG_TEXT          = (1 << 2),
  GST_PLAY_FLAG_VIS           = (1 << 3),
  GST_PLAY_FLAG_SOFT_VOLUME   = (1 << 4),
  GST_PLAY_FLAG_NATIVE_AUDIO  = (1 << 5),
  GST_PLAY_FLAG_NATIVE_VIDEO  = (1 << 6),
  GST_PLAY_FLAG_DOWNLOAD      = (1 << 7),
  GST_PLAY_FLAG_BUFFERING     = (1 << 8),
  GST_PLAY_FLAG_DEINTERLACE   = (1 << 9)
} GstPlayFlags;

Extra flags to configure the behaviour of the sinks.

GST_PLAY_FLAG_VIDEO

Enable rendering of the video stream

GST_PLAY_FLAG_AUDIO

Enable rendering of the audio stream

GST_PLAY_FLAG_TEXT

Enable rendering of subtitles

GST_PLAY_FLAG_VIS

Enable rendering of visualisations when there is no video stream.

GST_PLAY_FLAG_SOFT_VOLUME

Use software volume

GST_PLAY_FLAG_NATIVE_AUDIO

only allow native audio formats, this omits configuration of audioconvert and audioresample.

GST_PLAY_FLAG_NATIVE_VIDEO

only allow native video formats, this omits configuration of ffmpegcolorspace and videoscale.

GST_PLAY_FLAG_DOWNLOAD

enable progressice download buffering for selected formats.

GST_PLAY_FLAG_BUFFERING

enable buffering of the demuxed or parsed data.

GST_PLAY_FLAG_DEINTERLACE

deinterlace raw video (if native not forced).

Property Details

The "audio-sink" property

  "audio-sink"               GstElement*           : Read / Write

the audio output element to use (NULL = default sink).


The "connection-speed" property

  "connection-speed"         guint                 : Read / Write

Network connection speed in kbps (0 = unknown).

Allowed values: <= 4294967

Default value: 0


The "current-audio" property

  "current-audio"            gint                  : Read / Write

Get or set the currently playing audio stream. By default the first audio stream with data is played.

Allowed values: >= G_MAXULONG

Default value: -1


The "current-text" property

  "current-text"             gint                  : Read / Write

Get or set the currently playing subtitle stream. By default the first subtitle stream with data is played.

Allowed values: >= G_MAXULONG

Default value: -1


The "current-video" property

  "current-video"            gint                  : Read / Write

Get or set the currently playing video stream. By default the first video stream with data is played.

Allowed values: >= G_MAXULONG

Default value: -1


The "flags" property

  "flags"                    GstPlayFlags          : Read / Write

Control the behaviour of playbin.

Default value: Render the video stream|Render the audio stream|Render subtitles|Use software volume


The "frame" property

  "frame"                    GstBuffer*            : Read

Get the currently rendered or prerolled frame in the video sink. The GstCaps on the buffer will describe the format of the buffer.


The "n-audio" property

  "n-audio"                  gint                  : Read

Get the total number of available audio streams.

Allowed values: >= 0

Default value: 0


The "n-text" property

  "n-text"                   gint                  : Read

Get the total number of available subtitle streams.

Allowed values: >= 0

Default value: 0


The "n-video" property

  "n-video"                  gint                  : Read

Get the total number of available video streams.

Allowed values: >= 0

Default value: 0


The "source" property

  "source"                   GstElement*           : Read

Source element.


The "subtitle-encoding" property

  "subtitle-encoding"        gchar*                : Read / Write

Encoding to assume if input subtitles are not in UTF-8 encoding. If not set, the GST_SUBTITLE_ENCODING environment variable will be checked for an encoding to use. If that is not set either, ISO-8859-15 will be assumed.

Default value: NULL


The "subtitle-font-desc" property

  "subtitle-font-desc"       gchar*                : Write

Pango font description of font to be used for subtitle rendering.

Default value: NULL


The "suburi" property

  "suburi"                   gchar*                : Read / Write

Set the next subtitle URI that playbin will play. This property can be set from the about-to-finish signal to queue the next subtitle media file.

Default value: NULL


The "uri" property

  "uri"                      gchar*                : Read / Write

Set the next URI that playbin will play. This property can be set from the about-to-finish signal to queue the next media file.

Default value: NULL


The "video-sink" property

  "video-sink"               GstElement*           : Read / Write

the video output element to use (NULL = default sink).


The "vis-plugin" property

  "vis-plugin"               GstElement*           : Read / Write

the visualization element to use (NULL = default).


The "volume" property

  "volume"                   gdouble               : Read / Write

Get or set the current audio stream volume. 1.0 means 100%, 0.0 means mute. This uses a linear volume scale.

Allowed values: [0,10]

Default value: 1


The "mute" property

  "mute"                     gboolean              : Read / Write

Mute the audio channel without changing the volume.

Default value: FALSE


The "buffer-duration" property

  "buffer-duration"          gint64                : Read / Write

Buffer duration when buffering network streams.

Allowed values: >= G_MAXULONG

Default value: -1


The "buffer-size" property

  "buffer-size"              gint                  : Read / Write

Buffer size when buffering network streams.

Allowed values: >= G_MAXULONG

Default value: -1


The "text-sink" property

  "text-sink"                GstElement*           : Read / Write

the text output element to use (NULL = default textoverlay).


The "subpic-sink" property

  "subpic-sink"              GstElement*           : Read / Write

the subpicture output element to use (NULL = default dvdspu).


The "av-offset" property

  "av-offset"                gint64                : Read / Write

Control the synchronisation offset between the audio and video streams. Positive values make the audio ahead of the video and negative values make the audio go behind the video.

Default value: 0

Since 0.10.30


The "ring-buffer-max-size" property

  "ring-buffer-max-size"     guint64               : Read / Write

Max. amount of data in the ring buffer (bytes, 0 = ring buffer disabled).

Allowed values: <= G_MAXUINT

Default value: 0

Signal Details

The "about-to-finish" signal

void                user_function                      (GstPlayBin2 *playbin,
                                                        gpointer     user_data)      : Run Last

This signal is emitted when the current uri is about to finish. You can set the uri and suburi to make sure that playback continues.

This signal is emitted from the context of a GStreamer streaming thread.

playbin :

a GstPlayBin2

user_data :

user data set when the signal handler was connected.

The "audio-changed" signal

void                user_function                      (GstPlayBin2 *playbin,
                                                        gpointer     user_data)      : Run Last

This signal is emitted whenever the number or order of the audio streams has changed. The application will most likely want to select a new audio stream.

This signal may be emitted from the context of a GStreamer streaming thread. You can use gst_message_new_application() and gst_element_post_message() to notify your application's main thread.

playbin :

a GstPlayBin2

user_data :

user data set when the signal handler was connected.

The "get-audio-tags" signal

GstTagList*         user_function                      (GstPlayBin2 *playbin,
                                                        gint         stream,
                                                        gpointer     user_data)      : Action

Action signal to retrieve the tags of a specific audio stream number. This information can be used to select a stream.

playbin :

a GstPlayBin2

stream :

an audio stream number

user_data :

user data set when the signal handler was connected.

Returns :

a GstTagList with tags or NULL when the stream number does not exist.

The "get-text-tags" signal

GstTagList*         user_function                      (GstPlayBin2 *playbin,
                                                        gint         stream,
                                                        gpointer     user_data)      : Action

Action signal to retrieve the tags of a specific text stream number. This information can be used to select a stream.

playbin :

a GstPlayBin2

stream :

a text stream number

user_data :

user data set when the signal handler was connected.

Returns :

a GstTagList with tags or NULL when the stream number does not exist.

The "get-video-tags" signal

GstTagList*         user_function                      (GstPlayBin2 *playbin,
                                                        gint         stream,
                                                        gpointer     user_data)      : Action

Action signal to retrieve the tags of a specific video stream number. This information can be used to select a stream.

playbin :

a GstPlayBin2

stream :

a video stream number

user_data :

user data set when the signal handler was connected.

Returns :

a GstTagList with tags or NULL when the stream number does not exist.

The "text-changed" signal

void                user_function                      (GstPlayBin2 *playbin,
                                                        gpointer     user_data)      : Run Last

This signal is emitted whenever the number or order of the text streams has changed. The application will most likely want to select a new text stream.

This signal may be emitted from the context of a GStreamer streaming thread. You can use gst_message_new_application() and gst_element_post_message() to notify your application's main thread.

playbin :

a GstPlayBin2

user_data :

user data set when the signal handler was connected.

The "video-changed" signal

void                user_function                      (GstPlayBin2 *playbin,
                                                        gpointer     user_data)      : Run Last

This signal is emitted whenever the number or order of the video streams has changed. The application will most likely want to select a new video stream.

This signal is usually emitted from the context of a GStreamer streaming thread. You can use gst_message_new_application() and gst_element_post_message() to notify your application's main thread.

playbin :

a GstPlayBin2

user_data :

user data set when the signal handler was connected.

The "convert-frame" signal

GstBuffer*          user_function                      (GstPlayBin2 *playbin,
                                                        GstCaps     *caps,
                                                        gpointer     user_data)      : Action

Action signal to retrieve the currently playing video frame in the format specified by caps. If caps is NULL, no conversion will be performed and this function is equivalent to the "frame" property.

playbin :

a GstPlayBin2

caps :

the target format of the frame

user_data :

user data set when the signal handler was connected.

Returns :

a GstBuffer of the current video frame converted to caps. The caps on the buffer will describe the final layout of the buffer data. NULL is returned when no current buffer can be retrieved or when the conversion failed.

The "get-audio-pad" signal

GstPad*             user_function                      (GstPlayBin2 *playbin,
                                                        gint         stream,
                                                        gpointer     user_data)      : Action

Action signal to retrieve the stream-selector sinkpad for a specific audio stream. This pad can be used for notifications of caps changes, stream-specific queries, etc.

playbin :

a GstPlayBin2

stream :

an audio stream number

user_data :

user data set when the signal handler was connected.

Returns :

a GstPad, or NULL when the stream number does not exist.

The "get-text-pad" signal

GstPad*             user_function                      (GstPlayBin2 *playbin,
                                                        gint         stream,
                                                        gpointer     user_data)      : Action

Action signal to retrieve the stream-selector sinkpad for a specific text stream. This pad can be used for notifications of caps changes, stream-specific queries, etc.

playbin :

a GstPlayBin2

stream :

a text stream number

user_data :

user data set when the signal handler was connected.

Returns :

a GstPad, or NULL when the stream number does not exist.

The "get-video-pad" signal

GstPad*             user_function                      (GstPlayBin2 *playbin,
                                                        gint         stream,
                                                        gpointer     user_data)      : Action

Action signal to retrieve the stream-selector sinkpad for a specific video stream. This pad can be used for notifications of caps changes, stream-specific queries, etc.

playbin :

a GstPlayBin2

stream :

a video stream number

user_data :

user data set when the signal handler was connected.

Returns :

a GstPad, or NULL when the stream number does not exist.

The "audio-tags-changed" signal

void                user_function                      (GstPlayBin2 *playbin,
                                                        gint         stream,
                                                        gpointer     user_data)      : Run Last

This signal is emitted whenever the tags of an audio stream have changed. The application will most likely want to get the new tags.

This signal may be emitted from the context of a GStreamer streaming thread. You can use gst_message_new_application() and gst_element_post_message() to notify your application's main thread.

playbin :

a GstPlayBin2

stream :

stream index with changed tags

user_data :

user data set when the signal handler was connected.

Since 0.10.24


The "text-tags-changed" signal

void                user_function                      (GstPlayBin2 *playbin,
                                                        gint         stream,
                                                        gpointer     user_data)      : Run Last

This signal is emitted whenever the tags of a text stream have changed. The application will most likely want to get the new tags.

This signal may be emitted from the context of a GStreamer streaming thread. You can use gst_message_new_application() and gst_element_post_message() to notify your application's main thread.

playbin :

a GstPlayBin2

stream :

stream index with changed tags

user_data :

user data set when the signal handler was connected.

Since 0.10.24


The "video-tags-changed" signal

void                user_function                      (GstPlayBin2 *playbin,
                                                        gint         stream,
                                                        gpointer     user_data)      : Run Last

This signal is emitted whenever the tags of a video stream have changed. The application will most likely want to get the new tags.

This signal may be emitted from the context of a GStreamer streaming thread. You can use gst_message_new_application() and gst_element_post_message() to notify your application's main thread.

playbin :

a GstPlayBin2

stream :

stream index with changed tags

user_data :

user data set when the signal handler was connected.

Since 0.10.24


The "source-setup" signal

void                user_function                      (GstPlayBin2 *playbin,
                                                        GstElement  *source,
                                                        gpointer     user_data)      : Run Last

This signal is emitted after the source element has been created, so it can be configured by setting additional properties (e.g. set a proxy server for an http source, or set the device and read speed for an audio cd source). This is functionally equivalent to connecting to the notify::source signal, but more convenient.

This signal is usually emitted from the context of a GStreamer streaming thread.

playbin :

a GstPlayBin2

source :

source element

user_data :

user data set when the signal handler was connected.

Since 0.10.33