The attached file documents the new, experimental, video output
overlays. These are for the 2.6.22 kernel.
While I'm happy with how it is used, the one thing that I am not sure
about is the name 'video output overlay'. I wonder if I shouldn't
rename it to 'Video Output OSD'. In theory at least it is possible to
have an MPEG decoder that mixes the video output with an OSD
framebuffer and then overlays that with a graphics card framebuffer.
Some feedback on this is welcome.
Regards,
Hans
Documentation for the new, experimental video output overlay buffer type.
Add a new section after section 4.3 (Video Output Interface):
Section 4.4. Video Output Overlay Interface
Status: experimental.
Also known as On-Screen Display
Video output overlay devices have the ability to mix the output video with a
framebuffer image. It is used to achieve the On-Screen Display feature.
Contrary to the Video Overlay Interface this framebuffer is normally
implemented on the video output board and not in the graphics card.
The actual operation of a video output overlay interface is identical
to that of the video overlay, see section 4.2 for more information.
4.4.1. Querying Capabilities
Devices supporting the video output overlay interface set the
V4L2_CAP_VIDEO_OUTPUT_OVERLAY flag in the capabilities field of struct
v4l2_capability returned by the VIDIOC_QUERYCAP.
ioctl VIDIOC_QUERYCAP: add the following to Table 2 (Device Capabilities Flags):
V4L2_CAP_VIDEO_OUTPUT_OVERLAY 0x00000400 The device supports the video output
overlay interface. This is typically used for On-Screen
Displays.
Status: experimental.
Section 3.5 (Buffers), Table 3-2 (enum v4l2_buf_type): add the following:
V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY 8 Buffer for a video output overlay, see
Section 4.4.
Status: experimental.
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