How to Use the fspp Filter in FFmpeg

This guide explains how to use the fspp (Fast Simple Post Processing) filter in FFmpeg to improve video quality. You will learn what the filter does, its key parameters, and practical command-line examples to reduce compression artifacts, banding, and blockiness in your videos.

What is the fspp Filter?

The fspp filter is a fast post-processing filter in FFmpeg designed to reduce compression artifacts (such as blockiness and ringing) from heavily compressed videos. It is a faster, optimized alternative to the standard spp (Simple Post Processing) filter. It works by applying a Discrete Cosine Transform (DCT) based thresholding algorithm to smooth out unwanted noise while preserving sharp edges.

Basic Syntax

To apply the fspp filter, use the -vf (video filter) flag in your FFmpeg command:

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

Key Parameters

You can customize the behavior of the fspp filter using several parameters, passed as key=value pairs separated by colons:

• quality: Sets the quality of the post-processing.
  • Acceptable values: 4 (good/default) or 5 (best quality, but slower).
• qp: Forces a constant quantization parameter (QP). If not specified, the filter uses the QP from the source video.
• strength: Adjusts the filter strength.
  • Range: -15 to 32. The default is 0 (automatic based on QP). Higher values result in stronger deblocking but may blur fine details.
• use_bframe_qp: Enables or disables the use of B-frame QP.
  • Values: 0 (disabled) or 1 (enabled, default).

Practical Examples

1. Maximum Quality Deblocking

To get the highest quality deblocking and artifact reduction, set the quality parameter to 5:

ffmpeg -i input.mp4 -vf fspp=quality=5 output.mp4

2. Increasing Filter Strength for Highly Compressed Videos

If your input video is highly pixelated or blocky, you can manually increase the filter strength:

ffmpeg -i input.mp4 -vf fspp=quality=4:strength=10 output.mp4

3. Forcing a Constant Quantization Parameter (QP)

If your input video lacks QP metadata (which is common with some modern web formats), you can force a QP value to make the filter work effectively:

ffmpeg -i input.mp4 -vf fspp=qp=25 output.mp4

When to Use fspp

The fspp filter is highly effective when restoring low-bitrate archive videos, old cell phone footage, or highly compressed internet streams. Because it is computationally lighter than spp and uspp, it is ideal for systems with limited processing power.