FFmpeg Deinterlace: Top or Bottom Field First

Deinterlacing video correctly requires knowing the correct field order (parity)—either Top Field First (TFF) or Bottom Field First (BFF). This article explains how to specify and override field parity in FFmpeg using deinterlacing filters like yadif and bwdif, ensuring smooth playback without interlacing artifacts or judder.

Specifying Parity with the Yadif Filter

The most common filter for deinterlacing in FFmpeg is yadif (Yet Another Deinterlacing Filter). You can control the field order using the parity parameter.

The parity parameter accepts the following values: * -1 (Auto): Automatically detects the field parity from the input metadata (default). * 0 (TFF): Forces Top Field First. * 1 (BFF): Forces Bottom Field First.

Command Examples:

To force Top Field First (TFF) deinterlacing:

ffmpeg -i input.mp4 -vf "yadif=mode=0:parity=0" output.mp4

To force Bottom Field First (BFF) deinterlacing:

ffmpeg -i input.mp4 -vf "yadif=mode=0:parity=1" output.mp4

(Note: mode=0 outputs one frame for each frame, whereas mode=1 outputs one frame for each field, doubling the framerate).

Specifying Parity with the Bwdif Filter

If you are using bwdif (Bob Weaver Deinterlacing Filter), which often provides better visual quality than yadif, the syntax for specifying field parity remains the same.

The parity parameter values for bwdif are: * -1: Auto-detect * 0: Top Field First (TFF) * 1: Bottom Field First (BFF)

Command Example:

To deinterlace using bwdif with forced Top Field First:

ffmpeg -i input.mp4 -vf "bwdif=mode=0:parity=0" output.mp4

Overriding Metadata with Setfield

If the input file has incorrect container metadata, FFmpeg’s auto-detection will fail. You can explicitly set the field order of the input stream before it reaches the deinterlacer by using the setfield filter in your filter chain.

Command Example:

To mark the input as TFF and then apply deinterlacing:

ffmpeg -i input.mp4 -vf "setfield=tff,yadif=mode=0:parity=-1" output.mp4