multifdsink

multifdsink — Send data to multiple filedescriptors

Properties

gboolean handle-read Read / Write

Signals

void add Action
void add-full Action
void client-added Run Last
void client-fd-removed Run Last
void client-removed Run Last
GstStructure* get-stats Action
void remove Action
void remove-flush Action

Types and Values

Object Hierarchy

    GObject
    ╰── GInitiallyUnowned
        ╰── GstObject
            ╰── GstElement
                ╰── GstBaseSink
                    ╰── GstMultiHandleSink
                        ╰── GstMultiFdSink

Description

This plugin writes incoming data to a set of file descriptors. The file descriptors can be added to multifdsink by emitting the “add” signal. For each descriptor added, the “client-added” signal will be called.

The multifdsink element needs to be set into READY, PAUSED or PLAYING state before operations such as adding clients are possible.

A client can also be added with the “add-full” signal that allows for more control over what and how much data a client initially receives.

Clients can be removed from multifdsink by emitting the “remove” signal. For each descriptor removed, the “client-removed” signal will be called. The “client-removed” signal can also be fired when multifdsink decides that a client is not active anymore or, depending on the value of the “recover-policy” property, if the client is reading too slowly. In all cases, multifdsink will never close a file descriptor itself. The user of multifdsink is responsible for closing all file descriptors. This can for example be done in response to the “client-fd-removed” signal. Note that multifdsink still has a reference to the file descriptor when the “client-removed” signal is emitted, so that "get-stats" can be performed on the descriptor; it is therefore not safe to close the file descriptor in the “client-removed” signal handler, and you should use the “client-fd-removed” signal to safely close the fd.

Multifdsink internally keeps a queue of the incoming buffers and uses a separate thread to send the buffers to the clients. This ensures that no client write can block the pipeline and that clients can read with different speeds.

When adding a client to multifdsink, the “sync-method” property will define which buffer in the queued buffers will be sent first to the client. Clients can be sent the most recent buffer (which might not be decodable by the client if it is not a keyframe), the next keyframe received in multifdsink (which can take some time depending on the keyframe rate), or the last received keyframe (which will cause a simple burst-on-connect). Multifdsink will always keep at least one keyframe in its internal buffers when the sync-mode is set to latest-keyframe.

There are additional values for the “sync-method” property to allow finer control over burst-on-connect behaviour. By selecting the 'burst' method a minimum burst size can be chosen, 'burst-keyframe' additionally requires that the burst begin with a keyframe, and 'burst-with-keyframe' attempts to burst beginning with a keyframe, but will prefer a minimum burst size even if it requires not starting with a keyframe.

Multifdsink can be instructed to keep at least a minimum amount of data expressed in time or byte units in its internal queues with the “time-min” and “bytes-min” properties respectively. These properties are useful if the application adds clients with the “add-full” signal to make sure that a burst connect can actually be honored.

When streaming data, clients are allowed to read at a different rate than the rate at which multifdsink receives data. If the client is reading too fast, no data will be send to the client until multifdsink receives more data. If the client, however, reads too slowly, data for that client will be queued up in multifdsink. Two properties control the amount of data (buffers) that is queued in multifdsink: “buffers-max” and “buffers-soft-max”. A client that falls behind by “buffers-max” is removed from multifdsink forcibly.

A client with a lag of at least “buffers-soft-max” enters the recovery procedure which is controlled with the “recover-policy” property. A recover policy of NONE will do nothing, RESYNC_LATEST will send the most recently received buffer as the next buffer for the client, RESYNC_SOFT_LIMIT positions the client to the soft limit in the buffer queue and RESYNC_KEYFRAME positions the client at the most recent keyframe in the buffer queue.

multifdsink will by default synchronize on the clock before serving the buffers to the clients. This behaviour can be disabled by setting the sync property to FALSE. Multifdsink will by default not do QoS and will never drop late buffers.

Synopsis

Element Information

plugin

tcp

author

Thomas Vander Stichele <thomas at apestaart dot org>, Wim Taymans <wim@fluendo.com>

class

Sink/Network

Element Pads

name

sink

direction

sink

presence

always

details

ANY

Functions

Types and Values

struct GstMultiFdSink

struct GstMultiFdSink;

The multifdsink object structure.


enum GstRecoverPolicy

Possible values for the recovery procedure to use when a client consumes data too slow and has a backlag of more that soft-limit buffers.

Members

GST_RECOVER_POLICY_NONE

no recovering is done

 

GST_RECOVER_POLICY_RESYNC_LATEST

client is moved to last buffer

 

GST_RECOVER_POLICY_RESYNC_SOFT_LIMIT

client is moved to the soft limit

 

GST_RECOVER_POLICY_RESYNC_KEYFRAME

client is moved to latest keyframe

 

enum GstSyncMethod

This enum defines the selection of the first buffer that is sent to a new client.

Members

GST_SYNC_METHOD_LATEST

client receives most recent buffer

 

GST_SYNC_METHOD_NEXT_KEYFRAME

client receives next keyframe

 

GST_SYNC_METHOD_LATEST_KEYFRAME

client receives latest keyframe (burst)

 

GST_SYNC_METHOD_BURST

client receives specific amount of data

 

GST_SYNC_METHOD_BURST_KEYFRAME

client receives specific amount of data starting from latest keyframe

 

GST_SYNC_METHOD_BURST_WITH_KEYFRAME

client receives specific amount of data from a keyframe, or if there is not enough data after the keyframe, starting before the keyframe

 

enum GstClientStatus

This specifies the reason why a client was removed from multisocketsink and is received in the "client-removed" signal.

Members

GST_CLIENT_STATUS_OK

client is ok

 

GST_CLIENT_STATUS_CLOSED

client closed the socket

 

GST_CLIENT_STATUS_REMOVED

client is removed

 

GST_CLIENT_STATUS_SLOW

client is too slow

 

GST_CLIENT_STATUS_ERROR

client is in error

 

GST_CLIENT_STATUS_DUPLICATE

same client added twice

 

GST_CLIENT_STATUS_FLUSHING

client is flushing out the remaining buffers.

 

Property Details

The “handle-read” property

  “handle-read”              gboolean

Handle client reads and discard the data.

Flags: Read / Write

Default value: TRUE

Signal Details

The “add” signal

void
user_function (GstMultiFdSink *gstmultifdsink,
               gint            fd,
               gpointer        user_data)

Hand the given open file descriptor to multifdsink to write to.

Parameters

gstmultifdsink

the multifdsink element to emit this signal on

 

fd

the file descriptor to add to multifdsink

 

user_data

user data set when the signal handler was connected.

 

Flags: Action


The “add-full” signal

void
user_function (GstMultiFdSink              *gstmultifdsink,
               gint                         fd,
               GstMultiHandleSinkSyncMethod sync,
               GstFormat                    format_min,
               guint64                      value_min,
               GstFormat                    format_max,
               guint64                      value_max,
               gpointer                     user_data)

Hand the given open file descriptor to multifdsink to write to and specify the burst parameters for the new connection.

Parameters

gstmultifdsink

the multifdsink element to emit this signal on

 

fd

the file descriptor to add to multifdsink

 

sync

the sync method to use

 

format_min

the format of value_min

 

value_min

the minimum amount of data to burst expressed in format_min units.

 

format_max

the format of value_max

 

value_max

the maximum amount of data to burst expressed in format_max units.

 

user_data

user data set when the signal handler was connected.

 

Flags: Action


The “client-added” signal

void
user_function (GstMultiFdSink *gstmultifdsink,
               gint            fd,
               gpointer        user_data)

The given file descriptor was added to multifdsink. This signal will be emitted from the streaming thread so application should be prepared for that.

Parameters

gstmultifdsink

the multifdsink element that emitted this signal

 

fd

the file descriptor that was added to multifdsink

 

user_data

user data set when the signal handler was connected.

 

Flags: Run Last


The “client-fd-removed” signal

void
user_function (GstMultiFdSink *gstmultifdsink,
               gint            fd,
               gpointer        user_data)

The given file descriptor was removed from multifdsink. This signal will be emitted from the streaming thread so applications should be prepared for that.

In this callback, gstmultifdsink has removed all the information associated with fd and it is therefore not possible to call get-stats with fd . It is however safe to close() and reuse fd in the callback.

Parameters

gstmultifdsink

the multifdsink element that emitted this signal

 

fd

the file descriptor that was removed from multifdsink

 

user_data

user data set when the signal handler was connected.

 

Flags: Run Last


The “client-removed” signal

void
user_function (GstMultiFdSink                *gstmultifdsink,
               gint                           fd,
               GstMultiHandleSinkClientStatus status,
               gpointer                       user_data)

The given file descriptor is about to be removed from multifdsink. This signal will be emitted from the streaming thread so applications should be prepared for that.

gstmultifdsink still holds a handle to fd so it is possible to call the get-stats signal from this callback. For the same reason it is not safe to close() and reuse fd in this callback.

Parameters

gstmultifdsink

the multifdsink element that emitted this signal

 

fd

the file descriptor that is to be removed from multifdsink

 

status

the reason why the client was removed

 

user_data

user data set when the signal handler was connected.

 

Flags: Run Last


The “get-stats” signal

GstStructure*
user_function (GstMultiFdSink *gstmultifdsink,
               gint            fd,
               gpointer        user_data)

Get statistics about fd . This function returns a GValueArray to ease automatic wrapping for bindings.

Parameters

gstmultifdsink

the multifdsink element to emit this signal on

 

fd

the file descriptor to get stats of from multifdsink

 

user_data

user data set when the signal handler was connected.

 

Returns

a GValueArray with the statistics. The array contains guint64 values that represent respectively: total number of bytes sent, time when the client was added, time when the client was disconnected/removed, time the client is/was active, last activity time (in epoch seconds), number of buffers dropped. All times are expressed in nanoseconds (GstClockTime). The array can be 0-length if the client was not found.

Flags: Action


The “remove” signal

void
user_function (GstMultiFdSink *gstmultifdsink,
               gint            fd,
               gpointer        user_data)

Remove the given open file descriptor from multifdsink.

Parameters

gstmultifdsink

the multifdsink element to emit this signal on

 

fd

the file descriptor to remove from multifdsink

 

user_data

user data set when the signal handler was connected.

 

Flags: Action


The “remove-flush” signal

void
user_function (GstMultiFdSink *gstmultifdsink,
               gint            fd,
               gpointer        user_data)

Remove the given open file descriptor from multifdsink after flushing all the pending data to the fd.

Parameters

gstmultifdsink

the multifdsink element to emit this signal on

 

fd

the file descriptor to remove from multifdsink

 

user_data

user data set when the signal handler was connected.

 

Flags: Action

See Also

tcpserversink