Audio & Video Processing

Audio & Video Processing

Complete guide for audio and video processing.

Quick Reference

FFmpeg Commands

Common Formats

Video: MP4, WebM, MKV, AVI, MOV
Audio: MP3, AAC, WAV, FLAC, OGG
Codecs: H.264, H.265/​HEVC, VP9, AV1

Installation

# Ubuntu/​Debian
sudo apt install ffmpeg

# macOS
brew install ffmpeg

# Windows (Chocolatey)
choco install ffmpeg

Video Processing

Basic Conversion

# Video format conversion
ffmpeg -i input.avi output.mp4

# With codec specification
ffmpeg -i input.mp4 -c:v libx264 -c:a aac output.mp4

Quality Control

# CRF (Constant Rate Factor) - 0-51, lower = better quality
ffmpeg -i input.mp4 -c:v libx264 -crf 23 output.mp4

# Bitrate control
ffmpeg -i input.mp4 -c:v libx264 -b:v 2M output.mp4

# Two-pass encoding for better quality
ffmpeg -i input.mp4 -c:v libx264 -b:v 2M -pass 1 -f null /​dev/​null
ffmpeg -i input.mp4 -c:v libx264 -b:v 2M -pass 2 output.mp4

Resize and Scale

# Scale to specific resolution
ffmpeg -i input.mp4 -vf "scale=1920:1080" output.mp4

# Scale maintaining aspect ratio
ffmpeg -i input.mp4 -vf "scale=1280:-1" output.mp4  # Auto height

# Scale with padding (letterbox)
ffmpeg -i input.mp4 -vf "scale=1920:1080:force_original_aspect_ratio=decrease,pad=1920:1080:(ow-iw)/​2:(oh-ih)/​2" output.mp4

Trim and Cut

# Cut from timestamp to timestamp
ffmpeg -i input.mp4 -ss 00:01:00 -to 00:02:00 -c copy output.mp4

# Cut with duration
ffmpeg -i input.mp4 -ss 00:01:00 -t 30 -c copy output.mp4

# Fast seek (put -ss before input)
ffmpeg -ss 00:01:00 -i input.mp4 -t 30 -c copy output.mp4

Add Watermark

# Image watermark
ffmpeg -i input.mp4 -i logo.png -filter_complex "overlay=10:10" output.mp4

# Bottom right corner
ffmpeg -i input.mp4 -i logo.png -filter_complex "overlay=W-w-10:H-h-10" output.mp4

# Text watermark
ffmpeg -i input.mp4 -vf "drawtext=text='Copyright':fontsize=24:fontcolor=white:x=10:y=10" output.mp4

Audio Processing

Extract Audio

# Extract audio track
ffmpeg -i video.mp4 -vn -c:a copy audio.aac

# Convert to MP3
ffmpeg -i video.mp4 -vn -c:a libmp3lame -q:a 2 audio.mp3

Audio Conversion

# WAV to MP3
ffmpeg -i input.wav -c:a libmp3lame -b:a 320k output.mp3

# FLAC to MP3
ffmpeg -i input.flac -c:a libmp3lame -q:a 0 output.mp3

Audio Normalization

# Loudnorm filter (EBU R128)
ffmpeg -i input.mp3 -af loudnorm=I=-16:LRA=11:TP=-1.5 output.mp3

# Volume adjustment
ffmpeg -i input.mp3 -af "volume=2.0" output.mp3  # 2x louder

Merge Audio/​Video

# Replace audio track
ffmpeg -i video.mp4 -i audio.mp3 -c:v copy -c:a aac -map 0:v -map 1:a output.mp4

Thumbnails and Screenshots

Single Thumbnail

# At specific time
ffmpeg -i video.mp4 -ss 00:00:05 -frames:v 1 thumbnail.jpg

# Specific size
ffmpeg -i video.mp4 -ss 00:00:05 -frames:v 1 -vf "scale=320:180" thumbnail.jpg

Multiple Thumbnails

# Every N seconds
ffmpeg -i video.mp4 -vf "fps=1/​10" thumbnails_%03d.jpg  # Every 10 seconds

# Thumbnail sprite/​grid
ffmpeg -i video.mp4 -vf "fps=1/​10,scale=160:90,tile=10x10" sprite.jpg

GIF Creation

# Simple GIF
ffmpeg -i video.mp4 -ss 0 -t 5 -vf "fps=10,scale=320:-1" output.gif

# High quality GIF with palette
ffmpeg -i video.mp4 -ss 0 -t 5 -vf "fps=10,scale=320:-1:flags=lanczos,palettegen" palette.png
ffmpeg -i video.mp4 -i palette.png -ss 0 -t 5 -filter_complex "[0:v]fps=10,scale=320:-1:flags=lanczos[x];[x][1:v]paletteuse" output.gif

Streaming Formats

HLS (HTTP Live Streaming)

ffmpeg -i input.mp4 \
  -c:v libx264 -c:a aac \
  -hls_time 10 \
  -hls_list_size 0 \
  -hls_segment_filename "segment_%03d.ts" \
  output.m3u8

DASH

ffmpeg -i input.mp4 \
  -c:v libx264 -c:a aac \
  -f dash \
  output.mpd

Live Streaming

Stream to RTMP

# Stream file to RTMP
ffmpeg -re -i input.mp4 -c copy -f flv rtmp://server/​live/​stream

# Stream to YouTube
ffmpeg -i input.mp4 \
  -c:v libx264 -preset medium -b:v 4M \
  -c:a aac -b:a 128k \
  -f flv rtmp://a.rtmp.youtube.com/​live2/​YOUR_STREAM_KEY

Python Integration

FFmpeg Subprocess

import subprocess
import json

def get_video_info(video_path):
    """Get video metadata using ffprobe"""
    cmd = [
        'ffprobe',
        '-v', 'quiet',
        '-print_format', 'json',
        '-show_format',
        '-show_streams',
        video_path
    ]
    result = subprocess.run(cmd, capture_output=True, text=True)
    return json.loads(result.stdout)

def transcode_video(input_path, output_path, crf=23):
    """Transcode video with FFmpeg"""
    cmd = [
        'ffmpeg', '-i', input_path,
        '-c:v', 'libx264', '-crf', str(crf),
        '-c:a', 'aac',
        '-y', output_path
    ]
    subprocess.run(cmd, check=True)

MoviePy

from moviepy.editor import VideoFileClip

def process_video(input_path, output_path):
    clip = VideoFileClip(input_path)
    trimmed = clip.subclip(10, 60)
    resized = trimmed.resize(height=720)
    resized.write_videofile(output_path, codec='libx264')
    clip.close()

Encoding Presets

# Web-optimized MP4
ffmpeg -i input.mp4 \
  -c:v libx264 -preset slow -crf 22 \
  -c:a aac -b:a 128k \
  -movflags +faststart \
  output.mp4

# Archive quality
ffmpeg -i input.mp4 \
  -c:v libx264 -preset veryslow -crf 18 \
  -c:a flac \
  archive.mkv

# Mobile-optimized
ffmpeg -i input.mp4 \
  -c:v libx264 -preset fast -crf 28 \
  -vf "scale='min(720,iw)':-2" \
  -c:a aac -b:a 96k \
  mobile.mp4

Best Practices

1. Use hardware acceleration - NVENC, VAAPI, VideoToolbox
2. Optimize for web - faststart flag for streaming
3. Choose right codec - H.264 for compatibility, VP9/​AV1 for quality
4. Appropriate CRF - 18-23 for quality, 28+ for size
5. Two-pass for size - When file size matters
6. Process async - Queue long operations
7. Generate previews - Thumbnails and sprites
8. Validate input - Check format before processing
9. Clean temp files - Remove intermediate files
10. Monitor resources - CPU/​memory limits

When to Use This Skill

• Video format conversion
• Audio extraction and processing
• Thumbnail generation
• Streaming setup (HLS/​DASH)
• Video compression and optimization
• Batch media processing
• Live streaming configuration