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nmWTAI-Platform/3rd/FFmpeg-1.1/source/libvpx-1.3.0/examples/force_keyframe.txt

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@TEMPLATE encoder_tmpl.c
Forcing A Keyframe
==================
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ INTRODUCTION
This is an example demonstrating how to control placement of keyframes
on a frame-by-frame basis.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ INTRODUCTION
Configuration
-------------
Keyframes can be forced by setting the VPX_EFLAG_FORCE_KF bit of the
flags passed to `vpx_codec_control()`. In this example, we force a
keyframe every 8 frames.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PER_FRAME_CFG
if(!(frame_cnt & 7))
flags |= VPX_EFLAG_FORCE_KF;
else
flags &= ~VPX_EFLAG_FORCE_KF;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PER_FRAME_CFG
Observing The Effects
---------------------
The output of the encoder examples shows a 'K' rather than a dot '.'
when the encoder generates a keyframe. Note that every 8 frames a 'K'
is output.