How to Deinterlace Video with FFmpeg BWDIF

This article provides a quick and practical guide on how to deinterlace interlaced video files using FFmpeg’s high-quality bwdif (Bob Weaver Deinterlacing Filter). You will learn the basic command syntax, how the filter parameters work, and how to choose between outputting standard framerate or double framerate (bobbing) for smoother motion.

Why Use the BWDIF Filter?

The bwdif filter is a modern, motion-adaptive deinterlacing filter in FFmpeg. It is based on the popular yadif (Yet Another Deinterlacing Filter) but incorporates algorithms from the Weston 3D deinterlacer. This combination results in significantly better image quality, fewer visual artifacts, and sharper edges than older deinterlacing methods, while still maintaining fast processing speeds.

Basic Command Syntax

The most straightforward way to apply the bwdif filter is to use the -vf (video filter) flag in your FFmpeg command:

ffmpeg -i input.mp4 -vf bwdif output.mp4

This command uses the default settings of bwdif, which automatically detects the field order (top field first or bottom field first) and outputs one progressive frame for each interlaced frame (maintaining the original framerate).

Fine-Tuning BWDIF Parameters

To get the best results, you can customize the three primary parameters of the bwdif filter: mode, parity, and deint. The syntax for specifying these options is bwdif=mode:parity:deint.

1. Mode (Framerate Options)

The mode parameter determines how many frames are output per second: * 0 (or send_frame): Outputs 1 frame for each input frame. (Standard framerate, e.g., 30i becomes 30p). * 1 (or send_field): Outputs 1 frame for each input field. This is known as “bobbing” and doubles the framerate (e.g., 30i/60 fields per second becomes 60p), resulting in much smoother motion.

2. Parity (Field Order)

The parity parameter specifies which field is processed first. While FFmpeg usually detects this automatically, you can set it manually if the auto-detection fails: * -1 (or auto): Automatic detection (default). * 0 (or tff): Top field first. * 1 (or bff): Bottom field first.

3. Deint (Deinterlacing Target)

The deint parameter controls which frames the filter processes: * 0 (or all): Deinterlaces all frames (default). * 1 (or interlaced): Only deinterlaces frames that are flagged as interlaced.

Actionable Examples

Example 1: High-Quality Double Framerate (Smooth Motion)

To achieve the smoothest playback for sports or fast-moving footage, double the framerate by sending one frame per field:

ffmpeg -i input.ts -vf bwdif=mode=send_field:parity=auto:deint=all -c:v libx264 -crf 20 -c:a copy output.mp4

(Alternative short syntax: -vf bwdif=1:-1:0)

Example 2: Standard Framerate (Compatibility)

If you need to keep the original framerate (for example, converting 29.97i to 29.97p) to save file space or for specific device compatibility:

ffmpeg -i input.ts -vf bwdif=mode=send_frame:parity=auto:deint=all -c:v libx264 -crf 20 -c:a copy output.mp4

(Alternative short syntax: -vf bwdif=0:-1:0)