queue

queue — Simple data queue

Properties

guint current-level-buffers Read
guint current-level-bytes Read
guint64 current-level-time Read
gboolean flush-on-eos Read / Write
GstQueueLeaky leaky Read / Write
guint max-size-buffers Read / Write
guint max-size-bytes Read / Write
guint64 max-size-time Read / Write
guint min-threshold-buffers Read / Write
guint min-threshold-bytes Read / Write
guint64 min-threshold-time Read / Write
gboolean silent Read / Write

Signals

void overrun Run First
void pushing Run First
void running Run First
void underrun Run First

Types and Values

struct GstQueue
enum GstQueueLeaky

Object Hierarchy

    GObject
    ╰── GInitiallyUnowned
        ╰── GstObject
            ╰── GstElement
                ╰── GstQueue

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.

Synopsis

Element Information

plugin

coreelements

author

Erik Walthinsen <omega@cse.ogi.edu>

class

Generic

Element Pads

name

sink

direction

sink

presence

always

details

ANY

name

src

direction

source

presence

always

details

ANY

Functions

Types and Values

struct GstQueue

struct GstQueue;

Opaque GstQueue structure.


enum GstQueueLeaky

Buffer dropping scheme to avoid the queue to block when full.

Members

GST_QUEUE_NO_LEAK

Not Leaky

 

GST_QUEUE_LEAK_UPSTREAM

Leaky on upstream (new buffers)

 

GST_QUEUE_LEAK_DOWNSTREAM

Leaky on downstream (old buffers)

 

Property Details

The “current-level-buffers” property

  “current-level-buffers”    guint

Current number of buffers in the queue.

Flags: Read

Default value: 0


The “current-level-bytes” property

  “current-level-bytes”      guint

Current amount of data in the queue (bytes).

Flags: Read

Default value: 0


The “current-level-time” property

  “current-level-time”       guint64

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

Flags: Read

Default value: 0


The “flush-on-eos” property

  “flush-on-eos”             gboolean

Discard all data in the queue when an EOS event is received, and pass on the EOS event as soon as possible (instead of waiting until all buffers in the queue have been processed, which is the default behaviour).

Flushing the queue on EOS might be useful when capturing and encoding from a live source, to finish up the recording quickly in cases when the encoder is slow. Note that this might mean some data from the end of the recording data might be lost though (never more than the configured max. sizes though).

Flags: Read / Write

Default value: FALSE

Since 1.2


The “leaky” property

  “leaky”                    GstQueueLeaky

Where the queue leaks, if at all.

Flags: Read / Write

Default value: Not Leaky


The “max-size-buffers” property

  “max-size-buffers”         guint

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

Flags: Read / Write

Default value: 200


The “max-size-bytes” property

  “max-size-bytes”           guint

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

Flags: Read / Write

Default value: 10485760


The “max-size-time” property

  “max-size-time”            guint64

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

Flags: Read / Write

Default value: 1000000000


The “min-threshold-buffers” property

  “min-threshold-buffers”    guint

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

Flags: Read / Write

Default value: 0


The “min-threshold-bytes” property

  “min-threshold-bytes”      guint

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

Flags: Read / Write

Default value: 0


The “min-threshold-time” property

  “min-threshold-time”       guint64

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

Flags: Read / Write

Default value: 0


The “silent” property

  “silent”                   gboolean

Don't emit queue signals. Makes queues more lightweight if no signals are needed.

Flags: Read / Write

Default value: FALSE

Signal Details

The “overrun” signal

void
user_function (GstQueue *queue,
               gpointer  user_data)

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.

Parameters

queue

the queue instance

 

user_data

user data set when the signal handler was connected.

 

Flags: Run First


The “pushing” signal

void
user_function (GstQueue *queue,
               gpointer  user_data)

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

Parameters

queue

the queue instance

 

user_data

user data set when the signal handler was connected.

 

Flags: Run First


The “running” signal

void
user_function (GstQueue *queue,
               gpointer  user_data)

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.

Parameters

queue

the queue instance

 

user_data

user data set when the signal handler was connected.

 

Flags: Run First


The “underrun” signal

void
user_function (GstQueue *queue,
               gpointer  user_data)

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.

Parameters

queue

the queue instance

 

user_data

user data set when the signal handler was connected.

 

Flags: Run First