ffmpeg-ambient-audio

name	ffmpeg-ambient-audio
title	Generate Ambient Background Music with FFmpeg
description	Create layered ambient pad music using FFmpeg's aevalsrc filter. Generates loopable 15-second clips with slow vibrato, shimmer, and exponential decay, then loops to target duration. Mixes into video at low volume for BGM.
author	Hermi
date	2026-04-16T00:00:00.000Z
tags	["audio","ffmpeg","manim","bgm","ambient"]

When to Use

Create layered ambient pad music using FFmpeg's aevalsrc filter. Generates loopable 15-second clips with slow vibrato, shimmer, and exponential decay, then loops to target duration. Mixes into video at low volume for BGM.

Overview

Generates quiet ambient background music for tutorial/animation videos using pure FFmpeg — no external audio files or Python audio libraries needed.

Prerequisites

• FFmpeg installed (usually available)

Step‑by‑Step Procedure

1. Generate a 15-second ambient loop

ffmpeg -y -f lavfi \
  -i "aevalsrc='0.3*sin(2*PI*65.41*t)+0.25*sin(2*PI*98.0*t*(1+0.01*sin(2*PI*0.15*t)))+0.2*sin(2*PI*130.81*t)+0.15*sin(2*PI*164.81*t)*(0.5+0.5*sin(2*PI*0.05*t))+0.08*sin(2*PI*329.63*t)*exp(-0.02*t)':s=44100:d=15:c=stereo" \
  -af "afade=t=in:st=0:d=3,afade=t=out:st=12:d=3" \
  -c:a libvorbis -b:a 128k loop.ogg

Layered notes (C major chord progression):

• 65.41 Hz (C2) — deep bass drone, 30%
• 98.0 Hz (G2) — mid pad with slow vibrato, 25%
• 130.81 Hz (C3) — upper pad, 20%
• 164.81 Hz (E3) — shimmer with slow pulsing, 15%
• 329.63 Hz (C4) — ethereal high tone with exponential decay, 8%

Fade in/out of 3 seconds each for seamless looping.

2. Extend to full video duration

ffmpeg -y -stream_loop -1 -i loop.ogg -t <DURATION> -c:a libvorbis -b:a 128k bgm.ogg

-stream_loop -1 repeats until -t duration is reached.

3. Mix into video

If video has no audio track:

ffmpeg -y -i video.mp4 -i bgm.ogg \
  -filter_complex "[1:a]volume=0.15[a]" \
  -map 0:v -map "[a]" \
  -c:v copy -c:a aac -b:a 192k -shortest output.mp4

If video has existing audio, mix BGM underneath:

ffmpeg -y -i video.mp4 -i bgm.ogg \
  -filter_complex "[1:a]volume=0.15[a];[0:a][a]amix=inputs=2:duration=first:dropout_transition=3[aout]" \
  -map 0:v -map "[aout]" \
  -c:v copy -c:a aac -b:a 192k -shortest output.mp4

4. Verify

ffprobe -v quiet -show_entries format=duration,size \
  -show_entries stream=codec_type,codec_name -of json output.mp4

Key Parameters

Parameter	Purpose
s=44100	Sample rate (44.1 kHz CD quality)
c=stereo	Stereo output
afade=t=in/out	Smooth fade for loop seams
volume=0.15	BGM volume (15% — quiet background)
amix=dropout_transition=3	Graceful audio track blending
-shortest	Stop at shortest input (video duration)

Pitfalls

• Don't use raw sine waves without mixing — pure sine tones sound harsh. Layer at low volumes for ambient texture.
• Volume 0.15 is quiet — if too quiet, try 0.20-0.25. If too loud, try 0.10.
• -stream_loop -1 means infinite loop — always pair with -t <seconds>.
• Check if video has audio first (ffprobe -select_streams a), because the mix command differs.
• Vorbis for BGM (smaller file), AAC for final video output (better compatibility).

Verification

After mixing, the output video should have:

• Ambient pad music playing quietly underneath
• No audio clipping or distortion
• Smooth fade-in and fade-out at start/end
• Duration matches the video