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The QAbstractVideoSurface class is a base class for video presentation surfaces. More...
#include <QAbstractVideoSurface>
This class is under development and is subject to change.
This class is not part of the Qt GUI Framework Edition.
Inherits QObject.
This class was introduced in Qt 4.6.
enum | Error { NoError, UnsupportedFormatError, IncorrectFormatError, StoppedError, ResourceError } |
QAbstractVideoSurface ( QObject * parent = 0 ) | |
~QAbstractVideoSurface () | |
Error | error () const |
virtual bool | isFormatSupported ( const QVideoSurfaceFormat & format, QVideoSurfaceFormat * similar = 0 ) const |
bool | isStarted () const |
virtual bool | present ( const QVideoFrame & frame ) = 0 |
virtual bool | start ( const QVideoSurfaceFormat & format ) |
virtual void | stop () |
virtual QList<QVideoFrame::PixelFormat> | supportedPixelFormats ( QAbstractVideoBuffer::HandleType type = QAbstractVideoBuffer::NoHandle ) const = 0 |
QVideoSurfaceFormat | surfaceFormat () const |
void | startedChanged ( bool started ) |
void | supportedFormatsChanged () |
void | surfaceFormatChanged ( const QVideoSurfaceFormat & format ) |
void | setError ( Error error ) |
The QAbstractVideoSurface class is a base class for video presentation surfaces.
The QAbstractVideoSurface class defines the standard interface that video producers use to inter-operate with video presentation surfaces. It is not supposed to be instantiated directly. Instead, you should subclass it to create new video surfaces.
A video surface presents a continuous stream of identically formatted frames, where the format of each frame is compatible with a stream format supplied when starting a presentation.
A list of pixel formats a surface can present is given by the supportedPixelFormats() function, and the isFormatSupported() function will test if a complete video format is supported. In some cases when a format is not supported; isFormatSupported() may suggest a similar format. For example if a surface supports fixed set of resolutions it may suggest the smallest supported resolution that contains the proposed resolution.
The start() function takes a supported format and enables a video surface. Once started a surface will begin displaying the frames it receives in the present() function. Surfaces may hold a reference to the buffer of a presented video frame until a new frame is presented or streaming is stopped. The stop() function will disable a surface and a release any video buffers it holds references to.
This enum describes the errors that may be returned by the error() function.
Constant | Value | Description |
---|---|---|
QAbstractVideoSurface::NoError | 0 | No error occurred. |
QAbstractVideoSurface::UnsupportedFormatError | 1 | A video format was not supported. |
QAbstractVideoSurface::IncorrectFormatError | 2 | A video frame was not compatible with the format of the surface. |
QAbstractVideoSurface::StoppedError | 3 | The surface has not been started. |
QAbstractVideoSurface::ResourceError | 4 | The surface could not allocate some resource. |
Constructs a video surface with the given parent.
Destroys a video surface.
Returns the last error that occurred.
If a surface fails to start(), or stops unexpectedly this function can be called to discover what error occurred.
See also setError().
Tests a video format to determine if a surface can accept it. If the format isn't supported the surface may suggest a similar format that is supported.
Returns true if the format is supported by the surface, and false otherwise.
Indicates whether a video surface has been started.
Returns true if the surface has been started, and false otherwise.
Presents a video frame.
Returns true if the frame was presented, and false if an error occurred.
Not all surfaces will block until the presentation of a frame has completed. Calling present() on a non-blocking surface may fail if called before the presentation of a previous frame has completed. In such cases the surface may not return to a ready state until it's had an opportunity to process events.
If present() fails for any other reason the surface will immediately enter the stopped state and an error() value will be set.
A video surface must be in the started state for present() to succeed, and the format of the video frame must be compatible with the current video surface format.
See also error().
Sets the value of error() to error.
See also error().
Starts a video surface presenting format frames.
Returns true if the surface was started, and false if an error occurred.
See also isStarted() and stop().
Signals that the started state of a video surface has changed.
See also isStarted(), start(), and stop().
Stops a video surface presenting frames and releases any resources acquired in start().
See also isStarted() and start().
Signals that the set of formats supported by a video surface has changed.
See also supportedPixelFormats() and isFormatSupported().
Returns a list of pixel formats a video surface can present for a given handle type.
The pixel formats returned for the QAbstractVideoBuffer::NoHandle type are valid for any buffer that can be mapped in read-only mode.
Types that are first in the list can be assumed to be faster to render.
Returns the format of a video surface.
Signals that the configured format of a video surface has changed.
See also surfaceFormat() and start().
Copyright © 2009 Nokia Corporation and/or its subsidiary(-ies) | Trademarks | Qt 4.6.0 |