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diff --git a/Documentation/media/uapi/v4l/selection-api-005.rst b/Documentation/media/uapi/v4l/selection-api-005.rst deleted file mode 100644 index 5b47a28ac6d7..000000000000 --- a/Documentation/media/uapi/v4l/selection-api-005.rst +++ /dev/null @@ -1,34 +0,0 @@ -.. -*- coding: utf-8; mode: rst -*- - -******************************** -Comparison with old cropping API -******************************** - -The selection API was introduced to cope with deficiencies of previous -:ref:`API <crop>`, that was designed to control simple capture -devices. Later the cropping API was adopted by video output drivers. The -ioctls are used to select a part of the display were the video signal is -inserted. It should be considered as an API abuse because the described -operation is actually the composing. The selection API makes a clear -distinction between composing and cropping operations by setting the -appropriate targets. The V4L2 API lacks any support for composing to and -cropping from an image inside a memory buffer. The application could -configure a capture device to fill only a part of an image by abusing -V4L2 API. Cropping a smaller image from a larger one is achieved by -setting the field ``bytesperline`` at struct -:c:type:`v4l2_pix_format`. -Introducing an image offsets could be done by modifying field ``m_userptr`` -at struct -:c:type:`v4l2_buffer` before calling -:ref:`VIDIOC_QBUF`. Those operations should be avoided because they are not -portable (endianness), and do not work for macroblock and Bayer formats -and mmap buffers. The selection API deals with configuration of buffer -cropping/composing in a clear, intuitive and portable way. Next, with -the selection API the concepts of the padded target and constraints -flags are introduced. Finally, struct :c:type:`v4l2_crop` -and struct :c:type:`v4l2_cropcap` have no reserved -fields. Therefore there is no way to extend their functionality. The new -struct :c:type:`v4l2_selection` provides a lot of place -for future extensions. Driver developers are encouraged to implement -only selection API. The former cropping API would be simulated using the -new one. |