Abstract

author: Jonas Tingeborn
version: 1.0
category: Frame Rate Conversion
license: BSD
prerequisites:

  • FFmpegSource or some other video source filter that is able to properly read VFR clips

  • A timecodes file for the VFR clip, in matroska timecodes v2 format.

Description

This plugin converts variable frame rate clips to constant frame rate by introducing null frames.

By specifying a constant target frame rate (CFR) in the form of a numerator and denominator that yield a frame rate higher than the average frame rate of variable frame rate (VFR) clip, the plugin will insert null frames (exact copies of previous frame(s)) where needed to keep the framerate constant.

The foreseen values of this feature include:

  • Players or encoders that can’t deal with variable frames, either at all or by loosing audio sync, will be able to properly play a clip transcoded using this filter.

  • Since no frames are destroyed, and no frames created (only duplicated), it allows other filters, or encoders to simply drop duplicate frames when encoding, which should get the clip back to a VFR clip at the original frame rate, while still giving you the option to process the clip in avisynth without loss of audio sync.

  • Also, since only frame duping is done, it opens up for the possibility of intelligent post-processing, such as with mvtools, where dupe frames can be interpolated away, yielding a smoother playback experience.

Function signature

VfrToCfr(clip, "fpsnum", "fpsden", "debug")

Parameters

fpsnum

Numerator of the target FPS.
For example, if you wanted your target clip to have a constant NTSC frame rate, then this value would be 30000.
This parameter is mandatory.

fpsden

Denominator of the target FPS.
For a target NTSC frame rate, you’d set this to 1001 as 30000/1001 = 29.97.
This parameter is mandatory.

debug

Whether or not to show internal information (render it on top of the video)
This parameter is optional and defaults to false.

Example use

Convert a realmedia VFR video clip to CFR FILM

ffvideosource( "myclip.rm", timecodes="timecodes.txt" )
vfrtocfr( timecodes="timecodes.txt", fpsnum=24000, fpsden=1001 )

audiodub( ffaudiosource("myclip.rm") )

Hint: ffaudiosource may fail to load realmedia audio if it’s in cook format, so in that case just dump the audio to a wave file and load that file instead using wavsource or ffaudiosource.

Changelog

2013-01-15 v1.0

initial version