FFmpeg Video & Audio Encoding

FFmpeg Video & Audio Encoding

Complete guide to codec selection, quality optimization, and hardware acceleration.

Video Codecs

H.264 (libx264)

Most widely supported codec, excellent compression/quality balance.

Best for: Universal compatibility, streaming, web video

Quality range: CRF 17-28 (lower = better)

# High quality
ffmpeg -i input.mkv -c:v libx264 -preset slow -crf 18 -c:a copy output.mp4

# Standard quality (recommended)
ffmpeg -i input.mkv -c:v libx264 -preset medium -crf 23 -c:a copy output.mp4

# Fast encoding
ffmpeg -i input.mkv -c:v libx264 -preset fast -crf 23 -c:a copy output.mp4

H.265/HEVC (libx265)

25-50% better compression than H.264, slower encoding.

Best for: 4K video, file size reduction, archival

# High quality 4K
ffmpeg -i input.mkv -c:v libx265 -preset medium -crf 24 -c:a copy output.mp4

# Balanced quality
ffmpeg -i input.mkv -c:v libx265 -preset fast -crf 26 -c:a copy output.mp4

VP9 (libvpx-vp9)

Royalty-free, WebM format, good for YouTube and open-source projects.

Best for: YouTube, Chrome/Firefox, open platforms

# Quality-based (recommended)
ffmpeg -i input.mkv -c:v libvpx-vp9 -crf 30 -b:v 0 -c:a libopus output.webm

# Two-pass for better quality
ffmpeg -i input.mkv -c:v libvpx-vp9 -b:v 2M -pass 1 -an -f null /dev/null
ffmpeg -i input.mkv -c:v libvpx-vp9 -b:v 2M -pass 2 -c:a libopus output.webm

AV1 (libaom-av1, libsvtav1)

Next-generation codec, best compression, very slow encoding.

Best for: Future-proofing, maximum compression, low bandwidth

# Using libaom (slow, highest quality)
ffmpeg -i input.mkv -c:v libaom-av1 -crf 30 -b:v 0 -strict experimental output.mp4

# Using SVT-AV1 (faster)
ffmpeg -i input.mkv -c:v libsvtav1 -crf 30 -preset 5 output.mp4

Audio Codecs

AAC (Industry Standard)

Best quality for streaming, universal support.

# High quality
ffmpeg -i input.mp4 -c:a aac -b:a 192k output.mp4

# Standard quality
ffmpeg -i input.mp4 -c:a aac -b:a 128k output.mp4

# Low bitrate
ffmpeg -i input.mp4 -c:a aac -b:a 96k output.mp4

MP3 (libmp3lame)

Universal compatibility, good quality.

# Variable bitrate (best quality)
ffmpeg -i input.wav -c:a libmp3lame -q:a 0 output.mp3

# Constant bitrate
ffmpeg -i input.wav -c:a libmp3lame -b:a 192k output.mp3

Opus (libopus)

Best quality at low bitrates, ideal for voice and streaming.

# Voice (mono)
ffmpeg -i input.mp4 -c:a libopus -b:a 32k -ac 1 output.webm

# Music (stereo)
ffmpeg -i input.mp4 -c:a libopus -b:a 128k output.webm

FLAC (Lossless)

No quality loss, archival quality, larger files.

# Lossless audio
ffmpeg -i input.wav -c:a flac output.flac

# Extract audio losslessly
ffmpeg -i video.mp4 -c:a flac audio.flac

Quality Optimization

CRF (Constant Rate Factor)

Best for quality-focused encoding. Single-pass, adjusts bitrate for complexity.

CRF Scale:

• 0 = Lossless (huge files)
• 17-18 = Visually lossless
• 20-23 = High quality (recommended)
• 24-28 = Medium quality
• 30+ = Low quality
• 51 = Worst quality

# Visually lossless
ffmpeg -i input.mp4 -c:v libx264 -crf 18 -preset slow output.mp4

# High quality (recommended)
ffmpeg -i input.mp4 -c:v libx264 -crf 22 -preset medium output.mp4

# Balanced quality/size
ffmpeg -i input.mp4 -c:v libx264 -crf 25 -preset fast output.mp4

Bitrate-Based Encoding

Target specific file size or quality. Two-pass recommended.

# Calculate target bitrate
# bitrate = (target_size_MB * 8192) / duration_seconds - audio_bitrate

# Two-pass encoding (2600k video, 128k audio)
ffmpeg -y -i input.mkv -c:v libx264 -b:v 2600k -pass 1 -an -f null /dev/null
ffmpeg -i input.mkv -c:v libx264 -b:v 2600k -pass 2 -c:a aac -b:a 128k output.mp4

Presets (Speed vs Compression)

Trade-off between encoding speed and file size.

Available presets:

• ultrafast - Fastest, largest files
• superfast
• veryfast
• faster
• fast
• medium - Default balance
• slow - Better compression
• slower
• veryslow - Best compression
• placebo - Not recommended (minimal gains)

# Fast encoding (real-time)
ffmpeg -i input.mp4 -c:v libx264 -preset ultrafast -crf 23 output.mp4

# Balanced
ffmpeg -i input.mp4 -c:v libx264 -preset medium -crf 22 output.mp4

# Best compression (slow)
ffmpeg -i input.mp4 -c:v libx264 -preset veryslow -crf 20 output.mp4

Hardware Acceleration

NVIDIA NVENC

5-10x faster encoding, slightly larger files than software encoding.

Requirements: NVIDIA GPU (GTX 10xx or newer)

# H.264 with NVENC
ffmpeg -hwaccel cuda -i input.mp4 -c:v h264_nvenc -preset fast -crf 22 output.mp4

# H.265 with NVENC
ffmpeg -hwaccel cuda -i input.mp4 -c:v hevc_nvenc -preset slow -crf 24 output.mp4

# Quality levels (instead of CRF)
ffmpeg -hwaccel cuda -i input.mp4 -c:v h264_nvenc -preset slow -rc vbr -cq 22 output.mp4

NVENC Presets:

• default - Balanced
• slow - Better quality
• medium
• fast
• hp - High performance
• hq - High quality
• bd - Bluray disk
• ll - Low latency
• llhq - Low latency high quality
• llhp - Low latency high performance

Intel QuickSync (QSV)

Fast hardware encoding on Intel CPUs with integrated graphics.

Requirements: Intel CPU with Quick Sync Video support

# H.264 with QSV
ffmpeg -hwaccel qsv -c:v h264_qsv -i input.mp4 \
  -c:v h264_qsv -preset fast -global_quality 22 output.mp4

# H.265 with QSV
ffmpeg -hwaccel qsv -c:v hevc_qsv -i input.mp4 \
  -c:v hevc_qsv -preset medium -global_quality 24 output.mp4

# Quality levels
ffmpeg -hwaccel qsv -i input.mp4 -c:v h264_qsv -global_quality 20 output.mp4

AMD VCE/VCN

Hardware encoding on AMD GPUs.

Requirements: AMD GPU with VCE/VCN support

# H.264 with AMF
ffmpeg -hwaccel auto -i input.mp4 \
  -c:v h264_amf -quality balanced -rc cqp -qp 22 output.mp4

# H.265 with AMF
ffmpeg -hwaccel auto -i input.mp4 \
  -c:v hevc_amf -quality quality -rc cqp -qp 24 output.mp4

Apple VideoToolbox (macOS)

Hardware encoding on macOS devices.

# H.264 with VideoToolbox
ffmpeg -i input.mp4 -c:v h264_videotoolbox -b:v 2M output.mp4

# H.265 with VideoToolbox
ffmpeg -i input.mp4 -c:v hevc_videotoolbox -b:v 1.5M output.mp4

Performance Tuning

Multi-Threading

FFmpeg automatically uses multiple cores. Override if needed:

# Limit threads
ffmpeg -threads 4 -i input.mp4 -c:v libx264 output.mp4

# Auto (default)
ffmpeg -threads 0 -i input.mp4 -c:v libx264 output.mp4

Tune Options

Optimize encoder for specific content types:

# Film content
ffmpeg -i input.mp4 -c:v libx264 -tune film -crf 22 output.mp4

# Animation
ffmpeg -i input.mp4 -c:v libx264 -tune animation -crf 22 output.mp4

# Grain (film with noise)
ffmpeg -i input.mp4 -c:v libx264 -tune grain -crf 22 output.mp4

# Low latency streaming
ffmpeg -i input.mp4 -c:v libx264 -tune zerolatency -crf 22 output.mp4

# Screen content (sharp edges)
ffmpeg -i input.mp4 -c:v libx264 -tune stillimage -crf 22 output.mp4

Codec Selection Guide

Use Cases

Platform Compatibility

Best Practices

1. Use CRF for most tasks - Better than bitrate for variable content
2. Start with CRF 23 - Good balance, adjust based on results
3. Use slow preset - For archival and final delivery
4. Use fast preset - For previews and testing
5. Hardware acceleration - When speed is critical
6. Two-pass encoding - When file size is fixed
7. Match source frame rate - Don't increase FPS
8. Don't upscale resolution - Keep original or downscale
9. Test on short clips - Verify settings before full encode
10. Keep source files - Original quality for re-encoding

Troubleshooting

Poor Quality Output

# Lower CRF value
ffmpeg -i input.mp4 -c:v libx264 -crf 18 -preset slow output.mp4

# Use slower preset
ffmpeg -i input.mp4 -c:v libx264 -crf 22 -preset veryslow output.mp4

# Increase bitrate (two-pass)
ffmpeg -y -i input.mp4 -c:v libx264 -b:v 5M -pass 1 -an -f null /dev/null
ffmpeg -i input.mp4 -c:v libx264 -b:v 5M -pass 2 -c:a aac output.mp4

Slow Encoding

# Use faster preset
ffmpeg -i input.mp4 -c:v libx264 -preset ultrafast output.mp4

# Use hardware acceleration
ffmpeg -hwaccel cuda -i input.mp4 -c:v h264_nvenc output.mp4

# Reduce resolution
ffmpeg -i input.mp4 -vf scale=1280:-1 -c:v libx264 output.mp4

Large File Size

# Increase CRF
ffmpeg -i input.mp4 -c:v libx264 -crf 26 output.mp4

# Use better codec
ffmpeg -i input.mp4 -c:v libx265 -crf 26 output.mp4

# Two-pass with target bitrate
ffmpeg -y -i input.mp4 -c:v libx264 -b:v 1M -pass 1 -an -f null /dev/null
ffmpeg -i input.mp4 -c:v libx264 -b:v 1M -pass 2 -c:a aac output.mp4