[theora] Encoder keyframe frequency limited to >32

Andrew Bisson Andrew.Bisson at gossinteractive.com
Thu Apr 8 03:43:08 PDT 2010

I am using the directshow Theora encoder to compress a live video
stream.  A dump of the encoder settings is given below.  The starred
settings have been explicitly configured and the others are defaulted or
derived values.
These settings produce an even, dark (almost black) recorded result as
does any recording with Keyframe Freq  <= 32.  Keyframe Freq >32 works
perfectly.  The incoming video is at 5 fps.  
Although I can't find explicit documentation I presume that the Keyframe
Frequency is actually the keyframe interval measured in frames (what
h.264 would call GOP.)
 I need frequent keyframes  for input to a video editor although the
Changelog would suggest that perhaps this is not necessary (seeking to
non-keyframes is possible)

The Theora filter is Version 0.82.16930

**** Theora settings ****
Quality Mode                = False *
Quality                     = 10 *
Target Bitrate              = 256000 *
Keyframe Bitrate            = 384000
Fixed Keyframe Interval     = True *
Keyframe Freq               = 32 *
Keyframe Freq Min           = 8
Keyframe Auto Threshold     = 80
Sharpness                   = 0 *
Noise Sensitivity           = 1 *
Allow Dropped Frames        = False 
Quick Mode                  = True


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