Parity Filters

AviSynth includes these filters to change the parity state of a clip:

AssumeFrameBased / AssumeFieldBased

AviSynth keeps track of whether a given clip is field-based or frame-based. If the clip is field-based it also keeps track of the parity of each field – that is, whether it's the top or the bottom field. If the clip is frame-based it keeps track of the dominant field in each frame – that is, which field in the frame comes first when they are separated.

However, this information isn't necessarily correct, because field information usually isn't stored in video files and AviSynth's source filters just guess at it. AssumeFrameBased and AssumeFieldBased let you tell AviSynth the correct type of a clip. See this Doom9 thread for a bit more information.

AssumeFrameBased throws away the existing information and assumes that the clip is frame-based, with the bottom (even) field dominant in each frame. This happens to be what the source filters guess. If you want the top field dominant, use ComplementParity afterwards.

AssumeFieldBased throws away the existing information and assumes that the clip is field-based, with the even-numbered fields being bottom fields and the odd-numbered fields being top fields. If you want it the other way around, use ComplementParity afterwards.

Syntax and Parameters

AssumeFrameBased (clip)
AssumeFieldBased (clip)
clip

Source clip; all color formats supported.

AssumeTFF / AssumeBFF

AviSynth keeps track of whether a given clip is field-based or frame-based. If the clip is field-based it also keeps track of the parity of each field – that is, whether it's the top or the bottom field. If the clip is frame-based it keeps track of the dominant field in each frame – that is, which field in the frame comes first when they're separated.

However, this information isn't necessarily correct, because field information usually isn't stored in video files and AviSynth's source filters just normally default to assuming bottom field first (with the exception of the MPEG2Source plugin, which gets it right!). AssumeTFF and AssumeBFF let you tell AviSynth what you believe the field order a clip has.

AssumeTFF sets the field order to Top Field First and AssumeBFF to Bottom Field First. They do not change the actual field order, just the internal state flags in AviSynth relating to the source clip used.

Syntax and Parameters

AssumeTFF (clip)
AssumeBFF (clip)
clip

Source clip; all color formats supported.

Examples

AviSource("test.avi")
AssumeTFF()
SeparateFields()

Will always return the top field of the first frame followed by the bottom field of the first frame and so on.

AviSource("test.avi")
AssumeBFF()
SeparateFields()

Will always return the bottom field of the first frame followed by the top field of the first frame and so on.

ComplementParity

If the input clip is field-based, ComplementParity changes top fields to bottom fields and vice-versa. If the input clip is frame-based, it changes each frame's dominant field (bottom-dominant to top-dominant and vice-versa).

It does not change the actual field order, just the internal state flags in AviSynth relating to the source clip used.

Syntax and Parameters

ComplementParity (clip)
clip

Source clip; all color formats supported.

Changelog

Version

Changes

AviSynth 2.0.3

Added AssumeBFF / AssumeTFF filters.

$Date: 2022/03/17 21:41:11 $