Re: [PATCH] v4l: add V4L2_CID_MPEG_VIDEO_FORCE_FRAME_TYPE

On Wed, Jan 13, 2016 at 11:02 PM, Nicolas Dufresne
[off-list ref] wrote:

Le mercredi 13 janvier 2016 à 20:03 +0800, Wu-Cheng Li a écrit :

quoted

Some drivers also need a control like
V4L2_CID_MPEG_MFC51_VIDEO_FORCE_FRAME_TYPE to force an encoder frame
type. This patch adds a general V4L2_CID_MPEG_VIDEO_FORCE_FRAME_TYPE.

This control only affects the next queued buffer. There's no need to
clear the value after requesting an I frame. But all controls are set
in v4l2_ctrl_handler_setup. So a default DISABLED value is required.
Basically this control is like V4L2_CTRL_TYPE_BUTTON with parameters.
How to prevent a control from being set in v4l2_ctrl_handler_setup so
DISABLED value is not needed? Does it make sense not to set a control
if it is EXECUTE_ON_WRITE?

I don't like the way it's implemented. I don't know any decoder that
have a frame type forcing feature other they I-Frame. It would be much
more natural to use a toggle button control (and add more controls for
other types when needed) then trying to merge hypothetical toggles into
something that manually need to be set and disabled.

Using a button control sounds like a good idea. I'll discuss with other people
and reply tomorrow.

quoted

Wu-Cheng Li (1):
  v4l: add V4L2_CID_MPEG_VIDEO_FORCE_FRAME_TYPE.

 Documentation/DocBook/media/v4l/controls.xml | 23
+++++++++++++++++++++++
 drivers/media/v4l2-core/v4l2-ctrls.c         | 13 +++++++++++++
 include/uapi/linux/v4l2-controls.h           |  5 +++++
 3 files changed, 41 insertions(+)