VP8 encoder keyframe interval

[Matthew Heaney]

Does anyone know the magic incantation to force the VP8 video encoder
to honor the keyframe interval settings? I set the min and max
keyframe distance parameters to the same value (50, as the framerate
is 25 fps), and the keyframe mode to "disabled", yet the compressor is
only giving me a single keyframe at the beginning of the clip (which
is about 147 sec). What other settings should I use to get a keyframe
every 2 sec?

Thanks,
Matt

[James Zern]

The encoder wrapper in libvpx special cases min=max when the mode is
_AUTO and will force the encoder to produce keyframes on that
interval. To my knowledge _DISABLED will in fact disable key frame
production.

From vp8_cx_iface.c:vp8e_encode
/* Handle fixed keyframe intervals */
if (ctx->cfg.kf_mode == VPX_KF_AUTO
&& ctx->cfg.kf_min_dist == ctx->cfg.kf_max_dist)
{
if (++ctx->fixed_kf_cntr > ctx->cfg.kf_min_dist)
{
flags |= VPX_EFLAG_FORCE_KF;
ctx->fixed_kf_cntr = 0;
}
}

[Andy Shaules]

Disabled means you will pass in flag to encode function when you want a key
frame

Re-enable key frame and you will be good to go.

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