VideoSync Class Reference

Virtual base class for all video synchronization classes. More...

#include <vsync.h>

Inheritance diagram for VideoSync:

Public Member Functions
	VideoSync (VideoOutput *, int fi, int ri, bool intr)
	Used by BestMethod(VideoOutput*,uint,uint,bool) to initialize video synchronization method.
virtual	~VideoSync ()
virtual QString	getName (void) const =0
	Returns name of instanciated VSync method.
virtual bool	TryInit (void)=0
	Tries to initialize VSync method.
virtual void	Start (void)
	Start VSync; must be called from main thread.
virtual int	WaitForFrame (int sync_delay)=0
	Waits for next a frame or field.
int	getRefreshInterval (void) const
	Returns the (minimum) refresh interval of the output device.
void	setRefreshInterval (int ri)
	Sets the refresh interval of the output device.
virtual void	setFrameInterval (int fi)
virtual void	Stop (void)
	Stops VSync; must be called from main thread.
Static Public Member Functions
static VideoSync *	BestMethod (VideoOutput *, uint frame_interval, uint refresh_interval, bool interlaced)
	Returns the most sophisticated video sync method available.
Protected Member Functions
int64_t	GetTime (void)
int	CalcDelay (void)
	Calculates the delay to the next frame.
void	KeepPhase (void)
	Keep our nexttrigger from drifting too close to the exact retrace.
Protected Attributes
VideoOutput *	m_video_output
int	m_frame_interval
int	m_refresh_interval
bool	m_interlaced
int64_t	m_nexttrigger
int	m_delay
Static Protected Attributes
static int	m_forceskip = 0

Detailed Description

Virtual base class for all video synchronization classes.

This set of classes implements a variety of algorithms for synching video frames to a display. The better algorithms synchronize to the display's refresh rate, and also attempt to maintain phase with respect to the vertical retrace. The poorer algorithms simply try to display frames at a regular interval.

The factory method BestMethod tries subclasses in roughly quality order until one succeeds.

A/V sync methods may supply the nominal delay per frame. Other than that, video timing is entirely up to these classes. When WaitForFrame returns, it is time to show the frame.

Definition at line 45 of file vsync.h.

Constructor & Destructor Documentation

VideoSync::VideoSync	(	VideoOutput *	video_output,
		int	fi,
		int	ri,
		bool	intr
	)

Used by BestMethod(VideoOutput*,uint,uint,bool) to initialize video synchronization method.

Definition at line 115 of file vsync.cpp.

virtual VideoSync::~VideoSync ( ) [inline, virtual]

Definition at line 50 of file vsync.h.

Member Function Documentation

virtual QString VideoSync::getName ( void ) const [pure virtual]

Returns name of instanciated VSync method.

Implemented in DRMVideoSync, RTCVideoSync, BusyWaitVideoSync, USleepVideoSync, and DummyVideoSync.

Referenced by MythPlayer::InitAVSync().

virtual bool VideoSync::TryInit ( void ) [pure virtual]

Tries to initialize VSync method.

Implemented in DRMVideoSync, RTCVideoSync, BusyWaitVideoSync, USleepVideoSync, and DummyVideoSync.

void VideoSync::Start ( void ) [virtual]

Start VSync; must be called from main thread.

Start(void), WaitForFrame(void), and Stop(void) should always be called from same thread, to prevent bad interactions with threads.

Reimplemented in DRMVideoSync.

Definition at line 131 of file vsync.cpp.

Referenced by MythPlayer::DisplayPauseFrame(), MythPlayer::InitAVSync(), MythPlayer::PrebufferEnoughFrames(), and MythPlayer::VideoStart().

virtual int VideoSync::WaitForFrame ( int sync_delay ) [pure virtual]

Waits for next a frame or field.

Returns delay to real frame timing in usec

Start(void), WaitForFrame(void), and Stop(void) should always be called from same thread, to prevent bad interactions with threads.

Parameters:

sync_delay

time until the desired frame or field

See also:: CalcDelay(void), KeepPhase(void)

Implemented in DRMVideoSync, RTCVideoSync, BusyWaitVideoSync, USleepVideoSync, and DummyVideoSync.

Referenced by MythPlayer::AVSync().

int VideoSync::getRefreshInterval ( void ) const [inline]

Returns the (minimum) refresh interval of the output device.

Definition at line 78 of file vsync.h.

Referenced by MythPlayer::CanSupportDoubleRate(), and MythPlayer::ReinitVideo().

void VideoSync::setRefreshInterval ( int ri ) [inline]

Sets the refresh interval of the output device.

Definition at line 80 of file vsync.h.

Referenced by MythPlayer::ReinitVideo().

virtual void VideoSync::setFrameInterval ( int fi ) [inline, virtual]

Definition at line 82 of file vsync.h.

Referenced by MythPlayer::ChangeSpeed(), and MythPlayer::SetVideoParams().

virtual void VideoSync::Stop ( void ) [inline, virtual]

Stops VSync; must be called from main thread.

Start(void), WaitForFrame(void), and Stop(void) should always be called from same thread, to prevent bad interactions with threads.

Definition at line 90 of file vsync.h.

VideoSync * VideoSync::BestMethod	(	VideoOutput *	video_output,
		uint	frame_interval,
		uint	refresh_interval,
		bool	interlaced
	)			`[static]`

Returns the most sophisticated video sync method available.

Definition at line 76 of file vsync.cpp.

Referenced by MythPlayer::VideoStart().

int64_t VideoSync::GetTime ( void ) [protected]

Definition at line 124 of file vsync.cpp.

Referenced by CalcDelay(), and Start().

int VideoSync::CalcDelay ( void ) [protected]

Calculates the delay to the next frame.

Regardless of the timing method, if delay is greater than four full frames (could be greater than 20 or greater than 200), we don't want to freeze while waiting for a huge delay. Instead, contine playing video at half speed and continue to read new audio and video frames from the file until the sync is 'in the ballpark'. Also prevent the nexttrigger from falling too far in the past in case we are trying to speed up video output faster than possible.

Definition at line 147 of file vsync.cpp.

Referenced by USleepVideoSync::WaitForFrame(), BusyWaitVideoSync::WaitForFrame(), RTCVideoSync::WaitForFrame(), and DRMVideoSync::WaitForFrame().

void VideoSync::KeepPhase ( void ) [protected]

Keep our nexttrigger from drifting too close to the exact retrace.

If delay is near zero, some frames will be delay < 0 and others delay > 0 which would cause continous rapid fire stuttering. This method is only useful for those sync methods where WaitForFrame targets hardware retrace rather than targeting nexttrigger. NOTE: deprecated in favor of handling phase issues in mythplayer's AVSync.

Definition at line 192 of file vsync.cpp.