ARDOUR::Engine_Slave Class Reference

#include <slave.h>

Inheritance diagram for ARDOUR::Engine_Slave:

Public Member Functions
	Engine_Slave (AudioEngine &)
	~Engine_Slave ()
bool	speed_and_position (double &speed, framepos_t &pos)
bool	starting () const
bool	locked () const
bool	ok () const
framecnt_t	resolution () const
bool	requires_seekahead () const
bool	is_always_synced () const
Public Member Functions inherited from ARDOUR::Slave
	Slave ()
virtual	~Slave ()
virtual framecnt_t	seekahead_distance () const
virtual bool	give_slave_full_control_over_transport_speed () const
virtual std::string	approximate_current_delta () const

Private Attributes
AudioEngine &	engine
bool	_starting

Detailed Description

Definition at line 494 of file slave.h.

Constructor & Destructor Documentation

Engine_Slave::Engine_Slave

(

AudioEngine &

e

)

Definition at line 30 of file engine_slave.cc.

Engine_Slave::~Engine_Slave

(

)

Definition at line 39 of file engine_slave.cc.

Member Function Documentation

bool ARDOUR::Engine_Slave::is_always_synced ( ) const

inlinevirtual

Returns

- when returning true, ARDOUR will use transport speed 1.0 no matter what the slave returns

Reimplemented from ARDOUR::Slave.

Definition at line 507 of file slave.h.

bool Engine_Slave::locked ( ) const

virtual

reports to ARDOUR whether the Slave is currently synced to its external time source.

Returns

- when returning false, the transport will stop rolling

Implements ARDOUR::Slave.

Definition at line 44 of file engine_slave.cc.

bool Engine_Slave::ok ( ) const

virtual

reports to ARDOUR whether the slave is in a sane state

Returns

- when returning false, the transport will be stopped and the slave disconnected from ARDOUR.

Implements ARDOUR::Slave.

Definition at line 50 of file engine_slave.cc.

bool ARDOUR::Engine_Slave::requires_seekahead ( ) const

inlinevirtual

Returns

- when returning true, ARDOUR will wait for seekahead_distance() before transport starts rolling

Implements ARDOUR::Slave.

Definition at line 506 of file slave.h.

framecnt_t ARDOUR::Engine_Slave::resolution ( ) const

inlinevirtual

Returns

- the timing resolution of the Slave - If the distance of ARDOURs transport to the slave becomes greater than the resolution, sound will stop

Implements ARDOUR::Slave.

Definition at line 505 of file slave.h.

bool Engine_Slave::speed_and_position ( double &  speed, framepos_t &  position  )

virtual

This is the most important function to implement: Each process cycle, Session::follow_slave will call this method. and after the method call they should

Session::follow_slave will then try to follow the given position using a delay locked loop (DLL), starting with the first given transport speed. If the values of speed and position contradict each other, ARDOUR will always follow the position and disregard the speed. Although, a correct speed is important so that ARDOUR can sync to the master time source quickly.

For background information on delay locked loops, see http://www.kokkinizita.net/papers/usingdll.pdf

The method has the following precondition:

• Slave::ok() should return true, otherwise playback will stop immediately and the method will not be called
• when the references speed and position are passed into the Slave they are uninitialized

After the method call the following postconditions should be met:

• The first position value on transport start should be 0, otherwise ARDOUR will try to locate to the new position rather than move to it
• the references speed and position should be assigned to the Slaves current requested transport speed and transport position.
• Slave::resolution() should be greater than the maximum distance of ARDOURs transport position to the slaves requested transport position.
• Slave::locked() should return true, otherwise Session::no_roll will be called
• Slave::starting() should be false, otherwise the transport will not move until it becomes true *

Parameters

speed	- The transport speed requested
position	- The transport position requested

Returns

- The return value is currently ignored (see Session::follow_slave)

Implements ARDOUR::Slave.

Definition at line 56 of file engine_slave.cc.

bool ARDOUR::Engine_Slave::starting ( ) const

inlinevirtual

reports to ARDOUR whether the slave is in the process of starting to roll

Returns

- when returning false, transport will not move until this method returns true

Reimplemented from ARDOUR::Slave.

Definition at line 502 of file slave.h.

Member Data Documentation

bool ARDOUR::Engine_Slave::_starting

private

Definition at line 511 of file slave.h.

AudioEngine& ARDOUR::Engine_Slave::engine

private

Definition at line 510 of file slave.h.

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The documentation for this class was generated from the following files:

• /usr/local/music/src/ardour/4.0/libs/ardour/ardour/slave.h
• /usr/local/music/src/ardour/4.0/libs/ardour/engine_slave.cc