decodebin: GStreamer Base Plugins 1.0 Plugins Reference Manual

## decodebin decodebin |

## Properties

GstCaps * | caps | Read / Write
guint64 | connection-speed | Read / Write
gboolean | expose-all-streams | Read / Write
gint | high-percent | Read / Write
gint | low-percent | Read / Write
guint | max-size-buffers | Read / Write
guint | max-size-bytes | Read / Write
guint64 | max-size-time | Read / Write
gboolean | post-stream-topology | Read / Write
GstCaps * | sink-caps | Read / Write
gchar * | subtitle-encoding | Read / Write
gboolean | use-buffering | Read / Write

## Signals

gboolean | autoplug-continue | Run Last
GValueArray* | autoplug-factories | Run Last
gboolean | autoplug-query | Run Last
GstAutoplugSelectResult | autoplug-select | Run Last
GValueArray* | autoplug-sort | Run Last
void | drained | Run Last
void | unknown-type | Run Last

## Types and Values

struct | GstDecodeBin

## Object Hierarchy

        GObject
        ╰── GInitiallyUnowned
            ╰── GstObject
                ╰── GstElement
                    ╰── GstBin
                        ╰── GstDecodeBin

## Implemented Interfaces

GstDecodeBin implements GstChildProxy.

## Description

GstBin that auto-magically constructs a decoding pipeline using available decoders and demuxers via auto-plugging.

decodebin is considered stable now and replaces the old decodebin element. uridecodebin uses decodebin internally and is often more convenient to use, as it creates a suitable source element as well.

## Synopsis

### Element Information

plugin | playback
author | Edward Hervey <edward.hervey@collabora.co.uk>, Sebastian Dröge <sebastian.droege@collabora.co.uk>
class | Generic/Bin/Decoder

### Element Pads

name | sink
direction | sink
presence | always
details | ANY

name | src_%u
direction | source
presence | sometimes
details | ANY

## Functions

## Types and Values

### struct GstDecodeBin

    struct GstDecodeBin;

The opaque GstDecodeBin data structure

## Property Details

### The `“caps”` property

      “caps”                     GstCaps *

The caps on which to stop decoding.

Flags: Read / Write

### The `“connection-speed”` property

      “connection-speed”         guint64

Network connection speed in kbps (0 = unknown).

Flags: Read / Write

Allowed values: <= 18446744073709551

Default value: 0

### The `“expose-all-streams”` property

      “expose-all-streams”       gboolean

Expose all streams, including those of unknown type or that don't match the 'caps' property.

Flags: Read / Write

Default value: TRUE

### The `“high-percent”` property

      “high-percent”             gint

High threshold percent for buffering to finish.

Flags: Read / Write

Allowed values: [0,100]

Default value: 99

### The `“low-percent”` property

      “low-percent”              gint

Low threshold percent for buffering to start.

Flags: Read / Write

Allowed values: [0,100]

Default value: 10

### The `“max-size-buffers”` property

      “max-size-buffers”         guint

Max amount of buffers in the queue (0=automatic).

Flags: Read / Write

Default value: 0

### The `“max-size-bytes”` property

      “max-size-bytes”           guint

Max amount of bytes in the queue (0=automatic).

Flags: Read / Write

Default value: 0

### The `“max-size-time”` property

      “max-size-time”            guint64

Max amount of time in the queue (in ns, 0=automatic).

Flags: Read / Write

Default value: 0

### The `“post-stream-topology”` property

      “post-stream-topology”     gboolean

Post stream-topology messages.

Flags: Read / Write

Default value: FALSE

### The `“sink-caps”` property

      “sink-caps”                GstCaps *

The caps of the input data. (NULL = use typefind element).

Flags: Read / Write

### The `“subtitle-encoding”` property

      “subtitle-encoding”        gchar *

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.

Flags: Read / Write

Default value: NULL

### The `“use-buffering”` property

      “use-buffering”            gboolean

Emit GST_MESSAGE_BUFFERING based on low-/high-percent thresholds.

Flags: Read / Write

Default value: FALSE

## Signal Details

### The `“autoplug-continue”` signal

    gboolean
    user_function (GstDecodeBin *bin,
                   GstPad       *pad,
                   GstCaps      *caps,
                   gpointer      user_data)

This signal is emitted whenever decodebin finds a new stream. It is emitted before looking for any elements that can handle that stream.

Invocation of signal handlers stops after the first signal handler returns FALSE. Signal handlers are invoked in the order they were connected in.

#### Parameters

bin | The decodebin. |
pad | The GstPad. |
caps | The GstCaps found. |
user_data | user data set when the signal handler was connected. |

#### Returns

TRUE if you wish decodebin to look for elements that can handle the given `caps` . If FALSE, those caps will be considered as final and the pad will be exposed as such (see 'pad-added' signal of GstElement).

Flags: Run Last

### The `“autoplug-factories”` signal

    GValueArray*
    user_function (GstDecodeBin *bin,
                   GstPad       *pad,
                   GstCaps      *caps,
                   gpointer      user_data)

This function is emited when an array of possible factories for `caps` on `pad` is needed. Decodebin will by default return an array with all compatible factories, sorted by rank.

If this function returns NULL, `pad` will be exposed as a final caps.

If this function returns an empty array, the pad will be considered as having an unhandled type media type.

Only the signal handler that is connected first will ever by invoked. Don't connect signal handlers with the G_CONNECT_AFTER flag to this signal, they will never be invoked!

#### Parameters

bin | The decodebin. |
pad | The GstPad. |
caps | The GstCaps found. |
user_data | user data set when the signal handler was connected. |

#### Returns

a GValueArray* with a list of factories to try. The factories are by default tried in the returned order or based on the index returned by "autoplug-select".

Flags: Run Last

### The `“autoplug-query”` signal

    gboolean
    user_function (GstDecodeBin *bin,
                   GstPad       *pad,
                   GstElement   *child,
                   GstQuery     *query,
                   gpointer      user_data)

This signal is emitted whenever an autoplugged element that is not linked downstream yet and not exposed does a query. It can be used to tell the element about the downstream supported caps for example.

#### Parameters

bin | The decodebin. |
pad | The GstPad. |
child | The child element doing the query |
query | The GstQuery. |
user_data | user data set when the signal handler was connected. |

#### Returns

TRUE if the query was handled, FALSE otherwise.

Flags: Run Last

### The `“autoplug-select”` signal

    GstAutoplugSelectResult
    user_function (GstDecodeBin      *bin,
                   GstPad            *pad,
                   GstCaps           *caps,
                   GstElementFactory *factory,
                   gpointer           user_data)

This signal is emitted once decodebin has found all the possible GstElementFactory that can be used to handle the given `caps` . For each of those factories, this signal is emitted.

The signal handler should return a GST_TYPE_AUTOPLUG_SELECT_RESULT enum value indicating what decodebin should do next.

A value of GST_AUTOPLUG_SELECT_TRY will try to autoplug an element from `factory` .

A value of GST_AUTOPLUG_SELECT_EXPOSE will expose `pad` without plugging any element to it.

A value of GST_AUTOPLUG_SELECT_SKIP will skip `factory` and move to the next factory.

The signal handler will not be invoked if any of the previously registered signal handlers (if any) return a value other than GST_AUTOPLUG_SELECT_TRY. Which also means that if you return GST_AUTOPLUG_SELECT_TRY from one signal handler, handlers that get registered next (again, if any) can override that decision.

#### Parameters

bin | The decodebin. |
pad | The GstPad. |
caps | The GstCaps. |
factory | A GstElementFactory to use. |
user_data | user data set when the signal handler was connected. |

#### Returns

a GST_TYPE_AUTOPLUG_SELECT_RESULT that indicates the required operation. the default handler will always return GST_AUTOPLUG_SELECT_TRY.

Flags: Run Last

### The `“autoplug-sort”` signal

    GValueArray*
    user_function (GstDecodeBin *bin,
                   GstPad       *pad,
                   GstCaps      *caps,
                   GValueArray  *factories,
                   gpointer      user_data)

Once decodebin has found the possible GstElementFactory objects to try for `caps` on `pad` , this signal is emited. The purpose of the signal is for the application to perform additional sorting or filtering on the element factory array.

The callee should copy and modify `factories` or return NULL if the order should not change.

Invocation of signal handlers stops after one signal handler has returned something else than NULL. Signal handlers are invoked in the order they were connected in. Don't connect signal handlers with the G_CONNECT_AFTER flag to this signal, they will never be invoked!

#### Parameters

bin | The decodebin. |
pad | The GstPad. |
caps | The GstCaps. |
factories | A GValueArray of possible GstElementFactory to use. |
user_data | user data set when the signal handler was connected. |

#### Returns

A new sorted array of GstElementFactory objects.

Flags: Run Last

### The `“drained”` signal

    void
    user_function (GstDecodeBin *bin,
                   gpointer      user_data)

This signal is emitted once decodebin has finished decoding all the data.

#### Parameters

bin | The decodebin |
user_data | user data set when the signal handler was connected. |

Flags: Run Last

### The `“unknown-type”` signal

    void
    user_function (GstDecodeBin *bin,
                   GstPad       *pad,
                   GstCaps      *caps,
                   gpointer      user_data)

This signal is emitted when a pad for which there is no further possible decoding is added to the decodebin.

#### Parameters

bin | The decodebin. |
pad | The new pad containing caps that cannot be resolved to a 'final' stream type. |
caps | The GstCaps of the pad that cannot be resolved. |
user_data | user data set when the signal handler was connected. |

Flags: Run Last