VideoSync Class Reference

#include <vsync.h>

Inheritance diagram for VideoSync:

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 an additonal delay per frame. Other than that, video timing is entirely up to these classes. When WaitForFrame returns, it is time to show the frame.

There is some basic support for interlaced video timing where the fields need to be displayed sequentially. Passing true for the interlaced flags for the constructors, BestMethod, and SetFrameInterval will cause us to wait for half the specified frame interval, if the refresh rate is sufficient to do so.

Definition at line 58 of file vsync.h.


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 void	WaitForFrame (int sync_delay)=0
	Waits for next a frame or field.
virtual void	AdvanceTrigger (void)=0
	Use the next frame or field for CalcDelay(void) and WaitForFrame(int).
void	SetFrameInterval (int fi, bool interlaced)
	Change frame interval and interlacing attributes.
bool	UsesFieldInterval (void) const
	Returns true AdvanceTrigger(void) advances a field at a time.
bool	UsesFrameInterval (void) const
	Returns true AdvanceTrigger(void) advances a frame at a time.
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
void	UpdateNexttrigger (void)
	Internal method to tells video synchronization method to use the next frame (or field, if interlaced) for CalcDelay() and WaitForFrame().
int	CalcDelay (void)
	Calculates the delay to the next frame.
void	KeepPhase (void)
	Keep our nexttrigger from drifting too close to the exact retrace.
Static Protected Member Functions
static void	OffsetTimeval (struct timeval &tv, int offset)
Protected Attributes
VideoOutput *	m_video_output
int	m_frame_interval
int	m_refresh_interval
bool	m_interlaced
struct timeval	m_nexttrigger
int	m_delay
Static Protected Attributes
static int	m_forceskip = 0

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 114 of file vsync.cpp.

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

Definition at line 63 of file vsync.h.

Member Function Documentation

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

Returns name of instanciated VSync method.

Implemented in DRMVideoSync, nVidiaVideoSync, OpenGLVideoSync, RTCVideoSync, BusyWaitVideoSync, and USleepVideoSync.

Referenced by NuppelVideoPlayer::InitAVSync().

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

Tries to initialize VSync method.

Implemented in DRMVideoSync, nVidiaVideoSync, OpenGLVideoSync, RTCVideoSync, BusyWaitVideoSync, and USleepVideoSync.

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 pthreads.

Reimplemented in DRMVideoSync, nVidiaVideoSync, and OpenGLVideoSync.

Definition at line 127 of file vsync.cpp.

Referenced by NuppelVideoPlayer::DisplayPauseFrame(), NuppelVideoPlayer::InitAVSync(), NuppelVideoPlayer::OutputVideoLoop(), NuppelVideoPlayer::PrebufferEnoughFrames(), OpenGLVideoSync::Start(), nVidiaVideoSync::Start(), and DRMVideoSync::Start().

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

Waits for next a frame or field.

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

Parameters:

sync_delay

time until the desired frame or field

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

Implemented in DRMVideoSync, nVidiaVideoSync, OpenGLVideoSync, RTCVideoSync, BusyWaitVideoSync, and USleepVideoSync.

Referenced by NuppelVideoPlayer::AVSync().

virtual void VideoSync::AdvanceTrigger ( void ) [pure virtual]

Use the next frame or field for CalcDelay(void) and WaitForFrame(int).

Implemented in DRMVideoSync, nVidiaVideoSync, OpenGLVideoSync, RTCVideoSync, BusyWaitVideoSync, and USleepVideoSync.

Referenced by NuppelVideoPlayer::AVSync().

void VideoSync::SetFrameInterval	(	int	fi,
		bool	interlaced
	)

Change frame interval and interlacing attributes.

Definition at line 135 of file vsync.cpp.

Referenced by NuppelVideoPlayer::DoPause(), NuppelVideoPlayer::DoPlay(), NuppelVideoPlayer::FallbackDeint(), NuppelVideoPlayer::OutputVideoLoop(), and NuppelVideoPlayer::SetScanType().

bool VideoSync::UsesFieldInterval ( void ) const [inline]

Returns true AdvanceTrigger(void) advances a field at a time.

Definition at line 96 of file vsync.h.

Referenced by NuppelVideoPlayer::OutputVideoLoop(), and NuppelVideoPlayer::SetScanType().

bool VideoSync::UsesFrameInterval ( void ) const [inline]

Returns true AdvanceTrigger(void) advances a frame at a time.

Definition at line 98 of file vsync.h.

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 pthreads.

Definition at line 106 of file vsync.h.

Referenced by OpenGLVideoSync::~OpenGLVideoSync().

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 73 of file vsync.cpp.

Referenced by NuppelVideoPlayer::OutputVideoLoop().

void VideoSync::OffsetTimeval	(	struct timeval &	tv,
		int	offset
	)			`[static, protected]`

Definition at line 146 of file vsync.cpp.

Referenced by CalcDelay(), KeepPhase(), UpdateNexttrigger(), USleepVideoSync::WaitForFrame(), BusyWaitVideoSync::WaitForFrame(), RTCVideoSync::WaitForFrame(), OpenGLVideoSync::WaitForFrame(), nVidiaVideoSync::WaitForFrame(), and DRMVideoSync::WaitForFrame().

void VideoSync::UpdateNexttrigger ( void ) [protected]

Internal method to tells video synchronization method to use the next frame (or field, if interlaced) for CalcDelay() and WaitForFrame().

Definition at line 166 of file vsync.cpp.

Referenced by USleepVideoSync::AdvanceTrigger(), BusyWaitVideoSync::AdvanceTrigger(), RTCVideoSync::AdvanceTrigger(), OpenGLVideoSync::AdvanceTrigger(), nVidiaVideoSync::AdvanceTrigger(), and DRMVideoSync::AdvanceTrigger().

int VideoSync::CalcDelay ( void ) [protected]

Calculates the delay to the next frame.

Regardless of the timing method, if delay is greater than two 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'.

Definition at line 185 of file vsync.cpp.

Referenced by USleepVideoSync::WaitForFrame(), BusyWaitVideoSync::WaitForFrame(), RTCVideoSync::WaitForFrame(), OpenGLVideoSync::WaitForFrame(), nVidiaVideoSync::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.

Definition at line 220 of file vsync.cpp.

Referenced by OpenGLVideoSync::AdvanceTrigger(), nVidiaVideoSync::AdvanceTrigger(), and DRMVideoSync::AdvanceTrigger().