queue

queue — Simple asynchronous data queue.

Synopsis

                    GstQueue;
                    GstQueueSize;

Object Hierarchy

  GObject
   +----GstObject
         +----GstElement
               +----GstQueue

Properties

  "current-level-buffers"    guint                 : Read
  "current-level-bytes"      guint                 : Read
  "current-level-time"       guint64               : Read
  "leaky"                    GstQueueLeaky         : Read / Write
  "max-size-buffers"         guint                 : Read / Write
  "max-size-bytes"           guint                 : Read / Write
  "max-size-time"            guint64               : Read / Write
  "min-threshold-buffers"    guint                 : Read / Write
  "min-threshold-bytes"      guint                 : Read / Write
  "min-threshold-time"       guint64               : Read / Write

Signals

  "overrun"                                        : Run First
  "running"                                        : Run First
  "underrun"                                       : Run First
  "pushing"                                        : Run First

Description

Data is queued until one of the limits specified by the "max-size-buffers", "max-size-bytes" and/or "max-size-time" properties has been reached. Any attempt to push more buffers into the queue will block the pushing thread until more space becomes available.

The queue will create a new thread on the source pad to decouple the processing on sink and source pad.

You can query how many buffers are queued by reading the "current-level-buffers" property. You can track changes by connecting to the notify::current-level-buffers signal (which like all signals will be emitted from the streaming thread). The same applies to the "current-level-time" and "current-level-bytes" properties.

The default queue size limits are 200 buffers, 10MB of data, or one second worth of data, whichever is reached first.

As said earlier, the queue blocks by default when one of the specified maximums (bytes, time, buffers) has been reached. You can set the "leaky" property to specify that instead of blocking it should leak (drop) new or old buffers.

The "underrun" signal is emitted when the queue has less data than the specified minimum thresholds require (by default: when the queue is empty). The "overrun" signal is emitted when the queue is filled up. Both signals are emitted from the context of the streaming thread.

Element Information

plugin

 coreelements

author

 Erik Walthinsen <omega@cse.ogi.edu>

class

 Generic

name

 src

direction

 source

presence

 always

details

 ANY

name

 sink

direction

 sink

presence

 always

details

 ANY

Details

GstQueue

typedef struct _GstQueue GstQueue;

Opaque GstQueue structure.

GstQueueSize

typedef struct {
    guint   buffers;
    guint   bytes;
    guint64 time;
} GstQueueSize;

Structure describing the size of a queue.

guint buffers;

 number of buffers

guint bytes;

 number of bytes

guint64 time;

 amount of time

Property Details

The "current-level-buffers" property

  "current-level-buffers"    guint                 : Read

Current number of buffers in the queue.

Default value: 0

The "current-level-bytes" property

  "current-level-bytes"      guint                 : Read

Current amount of data in the queue (bytes).

Default value: 0

The "current-level-time" property

  "current-level-time"       guint64               : Read

Current amount of data in the queue (in ns).

Default value: 0

The "leaky" property

  "leaky"                    GstQueueLeaky         : Read / Write

Where the queue leaks, if at all.

Default value: Not Leaky

The "max-size-buffers" property

  "max-size-buffers"         guint                 : Read / Write

Max. number of buffers in the queue (0=disable).

Default value: 200

The "max-size-bytes" property

  "max-size-bytes"           guint                 : Read / Write

Max. amount of data in the queue (bytes, 0=disable).

Default value: 10485760

The "max-size-time" property

  "max-size-time"            guint64               : Read / Write

Max. amount of data in the queue (in ns, 0=disable).

Default value: 1000000000

The "min-threshold-buffers" property

  "min-threshold-buffers"    guint                 : Read / Write

Min. number of buffers in the queue to allow reading (0=disable).

Default value: 0

The "min-threshold-bytes" property

  "min-threshold-bytes"      guint                 : Read / Write

Min. amount of data in the queue to allow reading (bytes, 0=disable).

Default value: 0

The "min-threshold-time" property

  "min-threshold-time"       guint64               : Read / Write

Min. amount of data in the queue to allow reading (in ns, 0=disable).

Default value: 0

Signal Details

The "overrun" signal

void                user_function                      (GstQueue *queue,
                                                        gpointer  user_data)      : Run First

Reports that the buffer became full (overrun). A buffer is full if the total amount of data inside it (num-buffers, time, size) is higher than the boundary values which can be set through the GObject properties.

queue :

 the queue instance

user_data :

 user data set when the signal handler was connected.

The "running" signal

void                user_function                      (GstQueue *queue,
                                                        gpointer  user_data)      : Run First

Reports that enough (min-threshold) data is in the queue. Use this signal together with the underrun signal to pause the pipeline on underrun and wait for the queue to fill-up before resume playback.

queue :

 the queue instance

user_data :

 user data set when the signal handler was connected.

The "underrun" signal

void                user_function                      (GstQueue *queue,
                                                        gpointer  user_data)      : Run First

Reports that the buffer became empty (underrun). A buffer is empty if the total amount of data inside it (num-buffers, time, size) is lower than the boundary values which can be set through the GObject properties.

queue :

 the queue instance

user_data :

 user data set when the signal handler was connected.

The "pushing" signal

void                user_function                      (GstQueue *queue,
                                                        gpointer  user_data)      : Run First

Reports when the queue has enough data to start pushing data again on the source pad.

queue :

 the queue instance

user_data :

 user data set when the signal handler was connected.
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