[MPlayer-dev-eng] New filter vf_ivtc, smart dropping of every 5th frame

[Johannes Guenther]

D Richard Felker III wrote:
> On Sun, Feb 16, 2003 at 10:22:46PM +0100, Johannes Guenther wrote:
>> Using only the (difference to the) last frame may lead to false
>> decisions. To decide whether to drop the frame in progress or not you
>> would need a threshold for the difference since the duplicated frame will
>> not be 100% the same (compression artefacts, etc.). But frames in dark
>> scenes with little motion will also fall under this threshold. With some
>> heuristics (drop only one frames out of five) you can avoid some of
>> this mistakes, but not all.
> Are you sure?? Unless the encoder used was totally broken, the
> duplicate frame will have all its macroblocks encoded as no change,
> and this should be bit-for-bit identical to the previous one.

In a ideal world...
Ok, serious: if you have good quality source material this may be true.
But if it comes to tv-captures (my case) it is not (noise).

Even without noise it depends on the encoder: Consider a high motion
scene where a frame gets encoded with some compression artefacts
(because the encoder is short of bits) and then suddenly the next frame
(the duplicate) has no motion at all. But no motion does not mean no
difference to the predecessor frame since that frame was altered by its
compression artefacts, thus the encoder will use the remaining bits to
enhance the quality of the duplicate (eliminate the compression
artefacts).

Greets,
	Johannes
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