Donson Intelligent Editing

Comprehensive guide for professional video and audio manipulation using FFmpeg and FFprobe.

Core Concepts

FFmpeg is the leading multimedia framework, able to decode, encode, transcode, mux, demux, stream, filter and play almost anything that humans and machines have created. It is a command-line tool that processes streams through a complex pipeline of demuxers, decoders, filters, encoders, and muxers.

Common Operations

# Basic Transcoding (MP4 to MKV)
ffmpeg -i input.mp4 output.mkv

# Change Video Codec (to H.265/HEVC)
ffmpeg -i input.mp4 -c:v libx265 -crf 28 -c:a copy output.mp4

# Extract Audio (No Video)
ffmpeg -i input.mp4 -vn -c:a libmp3lame -q:a 2 output.mp3

# Resize/Scale Video
ffmpeg -i input.mp4 -vf "scale=1280:720" output.mp4

# Cut Video (Start at 10s, Duration 30s)
ffmpeg -i input.mp4 -ss 00:00:10 -t 00:00:30 -c copy output.mp4

# Fast Precise Cut (Re-encoding only the cut points is complex, so standard re-encoding is safer for precision)
ffmpeg -ss 00:00:10 -i input.mp4 -to 00:00:40 -c:v libx264 -crf 23 -c:a aac output.mp4

# Concatenate Files (using demuxer)
# Create filelist.txt: file 'part1.mp4' \n file 'part2.mp4'
ffmpeg -f concat -safe 0 -i filelist.txt -c copy output.mp4

# Speed Up/Slow Down Video (2x speed)
ffmpeg -i input.mp4 -filter_complex "[0:v]setpts=0.5*PTS[v];[0:a]atempo=2.0[a]" -map "[v]" -map "[a]" output.mp4

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Processing Categories & When to Use

Codecs & Quality

| Option | Use When | |-----------|----------| | -c:v libx264 | Standard H.264 encoding (best compatibility) | | -c:v libx265 | H.265/HEVC encoding (best compression/quality) | | -crf [0-51] | Constant Rate Factor (lower is higher quality, 18-28 recommended) | | -preset | Encoding speed vs compression (ultrafast, medium, veryslow) | | -c:a copy | Pass-through audio without re-encoding (saves time/quality) |

Filters & Manipulation

| Filter | Use When | |-----------|----------| | scale | Changing resolution (e.g., scale=1920:-1 for 1080p width) | | crop | Removing edges (e.g., crop=w:h:x:y) | | transpose | Rotating video (1=90deg CW, 2=90deg CCW) | | fps | Changing frame rate (e.g., fps=30) | | drawtext | Adding text overlays/watermarks | | overlay | Picture-in-picture or adding image watermarks | | fade | Adding fade-in/out effects (e.g., fade=in:0:30 for first 30 frames) | | volume | Adjusting audio levels (e.g., volume=1.5 for 150% volume) | | setpts | Changing video speed (e.g., setpts=0.5*PTS for double speed) | | atempo | Changing audio speed without pitch shift (0.5 to 2.0) |

Inspection & Metadata

| Tool/Option | Use When | |-----------|----------| | ffprobe -v error -show_format -show_streams | Getting detailed technical info of a file | | -metadata title="Name" | Setting global metadata tags | | -map | Selecting specific streams (e.g., -map 0:v:0 -map 0:a:1) |

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Advanced: Complex Filtergraphs

Use filter_complex when you need to process multiple inputs or create non-linear filter chains.

# Example: Adding a watermark at the bottom right
ffmpeg -i input.mp4 -i watermark.png -filter_complex "overlay=main_w-overlay_w-10:main_h-overlay_h-10" output.mp4

# Example: Vertical Stack (2 videos)
ffmpeg -i top.mp4 -i bottom.mp4 -filter_complex "vstack=inputs=2" output.mp4

# Example: Side-by-Side (2 videos)
ffmpeg -i left.mp4 -i right.mp4 -filter_complex "hstack=inputs=2" output.mp4

# Example: Grid (4 videos 2x2)
ffmpeg -i v1.mp4 -i v2.mp4 -i v3.mp4 -i v4.mp4 -filter_complex "[0:v][1:v]hstack=inputs=2[top];[2:v][3:v]hstack=inputs=2[bottom];[top][bottom]vstack=inputs=2" output.mp4

# Example: Fade Transition (Simple crossfade between two clips)
# Requires manual offset calculation, using xfade is better
ffmpeg -i input1.mp4 -i input2.mp4 -filter_complex "xfade=transition=fade:duration=1:offset=9" output.mp4

Hardware Acceleration

| Platform | Codec | Command | |----------|-------|---------| | NVIDIA (NVENC) | H.264 | -c:v h264_nvenc | | Intel (QSV) | H.264 | -c:v h264_qsv | | Apple (VideoToolbox) | H.265 | -c:v hevc_videotoolbox |

Constraints & Error Handling

1. Stream Mapping: Always use -map for complex files to ensure you get the right audio/subtitle tracks.
2. Seeking: Put -ss *before* -i for fast seeking (input seeking), or *after* -i for accurate seeking (output seeking).
3. Format Support: Ensure the output container (extension) supports the codecs you've chosen.