- Qt 6.9
- Qt Multimedia
- C++ Classes
- QtMultimedia
- QAbstractVideoBuffer
- Qt 6.9.3 Reference Documentation

# QAbstractVideoBuffer Class

The QAbstractVideoBuffer class is an abstraction for video data. More...

Header: | `#include <QAbstractVideoBuffer>`
CMake: | `find_package(Qt6 REQUIRED COMPONENTS Multimedia)` `target_link_libraries(mytarget PRIVATE Qt6::Multimedia)`
qmake: | `QT += multimedia`
Since: | Qt 6.8

- List of all members, including inherited members

## Public Types

struct | MapData

## Public Functions

virtual | ~QAbstractVideoBuffer()
virtual QVideoFrameFormat | format() const = 0
virtual QAbstractVideoBuffer::MapData | map(QVideoFrame::MapMode mode) = 0
virtual void | unmap()

## Detailed Description

The QVideoFrame class makes use of a QAbstractVideoBuffer internally to reference a buffer of video data. Creating a subclass of QAbstractVideoBuffer allows you to construct video frames from preallocated or static buffers. The subclass can contain a hardware buffer, and implement access to the data by mapping the buffer to CPU memory.

The contents of a buffer can be accessed by mapping the buffer to memory using the map() function, which returns a structure containing information about plane layout of the current video data.

See also QVideoFrame, QVideoFrameFormat, and QVideoFrame::MapMode.

## Member Function Documentation

### `[virtual noexcept]` QAbstractVideoBuffer::~QAbstractVideoBuffer()

Destroys a video buffer.

### `[pure virtual]` QVideoFrameFormat QAbstractVideoBuffer::format() const

Gets QVideoFrameFormat of the underlying video buffer.

The format must be available upon construction of QVideoFrame. QVideoFrame will contain won instance of the given format, that can be detached and modified.

### `[pure virtual]` QAbstractVideoBuffer::MapData QAbstractVideoBuffer::map(QVideoFrame::MapMode mode)

Maps the planes of a video buffer to memory.

Returns a MapData structure that contains information about the plane layout of the mapped current video data. If the mapping fails, the method returns the default structure. For CPU memory buffers, the data is considered as already mapped, so the function just returns the plane layout of the preallocated underlying data.

The map mode indicates whether the contents of the mapped memory should be read from and/or written to the buffer. If the map mode includes the `QVideoFrame::ReadOnly` flag the mapped memory will be populated with the content of the buffer when initially mapped. If the map mode includes the `QVideoFrame::WriteOnly` flag the content of the possibly modified mapped memory will be written back to the buffer when unmapped.

When access to the data is no longer needed, the unmap function is called to release the mapped memory and possibly update the buffer contents.

If the format of the video data is multiplanar, the method may map the whole pixel data as a single plane. In this case, mapping a buffer with QVideoFrame will calculate additional planes from the specified line stride of the first plane, the frame height, and the data size.

### `[virtual]` void QAbstractVideoBuffer::unmap()

Releases the memory mapped by the map() function.

If the MapMode included the `QVideoFrame::WriteOnly` flag this will write the current content of the mapped memory back to the video frame.

For CPU video buffers, the function may be not overridden. The default implementation of `unmap` does nothing.

See also map().