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GstPtpClock

GstPtpClock — Special clock that synchronizes to a remote time provider via PTP (IEEE1588:2008).

Properties

guint domain Read / Write / Construct Only
guint64 grandmaster-clock-id Read
GstClock * internal-clock Read
guint64 master-clock-id Read

Object Hierarchy

    GObject
    ╰── GInitiallyUnowned
        ╰── GstObject
            ╰── GstClock
                ╰── GstSystemClock
                    ╰── GstPtpClock

Includes

#include <gst/net/net.h>

Description

GstPtpClock implements a PTP (IEEE1588:2008) ordinary clock in slave-only mode, that allows a GStreamer pipeline to synchronize to a PTP network clock in some specific domain.

The PTP subsystem can be initialized with gst_ptp_init(), which then starts a helper process to do the actual communication via the PTP ports. This is required as PTP listens on ports < 1024 and thus requires special privileges. Once this helper process is started, the main process will synchronize to all PTP domains that are detected on the selected interfaces.

gst_ptp_clock_new() then allows to create a GstClock that provides the PTP time from a master clock inside a specific PTP domain. This clock will only return valid timestamps once the timestamps in the PTP domain are known. To check this, you can use gst_clock_wait_for_sync(), the GstClock::synced signal and gst_clock_is_synced().

To gather statistics about the PTP clock synchronization, gst_ptp_statistics_callback_add() can be used. This gives the application the possibility to collect all kinds of statistics from the clock synchronization.

Functions

gst_ptp_init ()

gboolean
gst_ptp_init (guint64 clock_id,
              gchar **interfaces);

Initialize the GStreamer PTP subsystem and create a PTP ordinary clock in slave-only mode for all domains on the given interfaces with the given clock_id .

If clock_id is GST_PTP_CLOCK_ID_NONE, a clock id is automatically generated from the MAC address of the first network interface.

This function is automatically called by gst_ptp_clock_new() with default parameters if it wasn't called before.

Parameters

clock_id

PTP clock id of this process' clock or GST_PTP_CLOCK_ID_NONE

 

interfaces

network interfaces to run the clock on.

[transfer none][array zero-terminated=1][allow-none]

Returns

TRUE if the GStreamer PTP clock subsystem could be initialized.

Since: 1.6


gst_ptp_deinit ()

void
gst_ptp_deinit (void);

Deinitialize the GStreamer PTP subsystem and stop the PTP clock. If there are any remaining GstPtpClock instances, they won't be further synchronized to the PTP network clock.

Since: 1.6


gst_ptp_is_initialized ()

gboolean
gst_ptp_is_initialized (void);

Check if the GStreamer PTP clock subsystem is initialized.

Returns

TRUE if the GStreamer PTP clock subsystem is intialized.

Since: 1.6


gst_ptp_is_supported ()

gboolean
gst_ptp_is_supported (void);

Check if PTP clocks are generally supported on this system, and if previous initializations did not fail.

Returns

TRUE if PTP clocks are generally supported on this system, and previous initializations did not fail.

Since: 1.6


gst_ptp_clock_new ()

GstClock *
gst_ptp_clock_new (const gchar *name,
                   guint domain);

Creates a new PTP clock instance that exports the PTP time of the master clock in domain . This clock can be slaved to other clocks as needed.

If gst_ptp_init() was not called before, this will call gst_ptp_init() with default parameters.

This clock only returns valid timestamps after it received the first times from the PTP master clock on the network. Once this happens the GstPtpClock::internal-clock property will become non-NULL. You can check this with gst_clock_wait_for_sync(), the GstClock::synced signal and gst_clock_is_synced().

Parameters

name

Name of the clock

 

domain

PTP domain

 

Since: 1.6


GstPtpStatisticsCallback ()

gboolean
(*GstPtpStatisticsCallback) (guint8 domain,
                             const GstStructure *stats,
                             gpointer user_data);

The statistics can be the following structures:

GST_PTP_STATISTICS_NEW_DOMAIN_FOUND: "domain" G_TYPE_UINT The domain identifier of the domain "clock" GST_TYPE_CLOCK The internal clock that is slaved to the PTP domain

GST_PTP_STATISTICS_BEST_MASTER_CLOCK_SELECTED: "domain" G_TYPE_UINT The domain identifier of the domain "master-clock-id" G_TYPE_UINT64 PTP clock identifier of the selected master clock "master-clock-port" G_TYPE_UINT PTP port number of the selected master clock "grandmaster-clock-id" G_TYPE_UINT64 PTP clock identifier of the grandmaster clock

GST_PTP_STATISTICS_PATH_DELAY_MEASURED: "domain" G_TYPE_UINT The domain identifier of the domain "mean-path-delay-avg" GST_TYPE_CLOCK_TIME Average mean path delay "mean-path-delay" GST_TYPE_CLOCK_TIME Latest mean path delay "delay-request-delay" GST_TYPE_CLOCK_TIME Delay of DELAY_REQ / DELAY_RESP messages

GST_PTP_STATISTICS_TIME_UPDATED: "domain" G_TYPE_UINT The domain identifier of the domain "mean-path-delay-avg" GST_TYPE_CLOCK_TIME Average mean path delay "local-time" GST_TYPE_CLOCK_TIME Local time that corresponds to ptp-time "ptp-time" GST_TYPE_CLOCK_TIME Newly measured PTP time at local-time "estimated-ptp-time" GST_TYPE_CLOCK_TIME Estimated PTP time based on previous measurements "discontinuity" G_TYPE_INT64 Difference between estimated and measured PTP time "synced" G_TYPE_BOOLEAN Currently synced to the remote clock "r-squared" G_TYPE_DOUBLE R² of clock estimation regression "internal-time" GST_TYPE_CLOCK_TIME Internal time clock parameter "external-time" GST_TYPE_CLOCK_TIME External time clock parameter "rate-num" G_TYPE_UINT64 Internal/external rate numerator "rate-den" G_TYPE_UINT64 Internal/external rate denominator "rate" G_TYPE_DOUBLE Internal/external rate

If FALSE is returned, the callback is removed and never called again.

Parameters

domain

PTP domain identifier

 

stats

New statistics

 

user_data

Data passed to gst_ptp_statistics_callback_add()

 

gst_ptp_statistics_callback_add ()

gulong
gst_ptp_statistics_callback_add (GstPtpStatisticsCallback callback,
                                 gpointer user_data,
                                 GDestroyNotify destroy_data);

Installs a new statistics callback for gathering PTP statistics. See GstPtpStatisticsCallback for a list of statistics that are provided.

Parameters

callback

GstPtpStatisticsCallback to call

 

user_data

Data to pass to the callback

 

destroy_data

GDestroyNotify to destroy the data

 

Returns

Id for the callback that can be passed to gst_ptp_statistics_callback_remove()

Since: 1.6


gst_ptp_statistics_callback_remove ()

void
gst_ptp_statistics_callback_remove (gulong id);

Removes a PTP statistics callback that was previously added with gst_ptp_statistics_callback_add().

Parameters

id

Callback id to remove

 

Since: 1.6

Types and Values

GST_PTP_CLOCK_ID_NONE

#define GST_PTP_CLOCK_ID_NONE ((guint64) -1)

struct GstPtpClock

struct GstPtpClock;

Opaque GstPtpClock structure.


GST_PTP_STATISTICS_BEST_MASTER_CLOCK_SELECTED

#define GST_PTP_STATISTICS_BEST_MASTER_CLOCK_SELECTED "GstPtpStatisticsBestMasterClockSelected"

GST_PTP_STATISTICS_NEW_DOMAIN_FOUND

#define GST_PTP_STATISTICS_NEW_DOMAIN_FOUND           "GstPtpStatisticsNewDomainFound"

GST_PTP_STATISTICS_PATH_DELAY_MEASURED

#define GST_PTP_STATISTICS_PATH_DELAY_MEASURED        "GstPtpStatisticsPathDelayMeasured"

GST_PTP_STATISTICS_TIME_UPDATED

#define GST_PTP_STATISTICS_TIME_UPDATED               "GstPtpStatisticsTimeUpdated"

Property Details

The “domain” property

  “domain”                   guint

The PTP domain.

Flags: Read / Write / Construct Only

Allowed values: <= 255

Default value: 0


The “grandmaster-clock-id” property

  “grandmaster-clock-id”     guint64

Grand Master Clock ID.

Flags: Read

Default value: 0


The “internal-clock” property

  “internal-clock”           GstClock *

Internal clock.

Flags: Read


The “master-clock-id” property

  “master-clock-id”          guint64

Master Clock ID.

Flags: Read

Default value: 0

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