Video Editor - FFmpeg & Encoding Expert Expert guidance for video editing, encoding, and processing with ffmpeg. This skill covers container formats, codecs, encoding best practices, and quality optimization for video production workflows. When to Use This Skill Use this skill when: Encoding or transcoding video files Converting between container formats (MKV, MP4, etc.) Optimizing encoding settings for quality or file size Troubleshooting video quality issues Working with color spaces and color matrices Hardsubbing or softsubbing videos Preparing videos for specific platforms or devices Understanding why a video looks wrong after processing Core Concepts Container vs. Codec This distinction is critical. File extensions like .mkv or .mp4 are container formats that package already-compressed streams. The actual compression happens through codecs like H.264, H.265, VP9, or AV1. Concept What It Is Examples Container Wrapper that holds video/audio/subtitle streams MKV, MP4, AVI, MOV, WebM Codec Algorithm that compresses/decompresses video H.264, H.265/HEVC, VP9, AV1 Encoder Software that implements a codec x264, x265, libvpx, NVENC Remuxing vs. Reencoding Operation What It Does Quality Impact Speed Remuxing Moves streams between containers without re-compression None (lossless) Very fast Reencoding Decodes and re-encodes video with new settings Always loses quality Slow Rule of thumb: If you only need to change the container format, remux. Only reencode when absolutely necessary. Quality Principles What "Quality" Actually Means Video quality measures how closely the output resembles the source . Every processing step moves the video further from the original. There is no way to add quality - only preserve or lose it. Common Misconceptions Myth Reality Higher resolution = better quality Resolution is just dimensions; a 720p video can look better than a 4K one Higher bitrate = better quality Encoder efficiency matters more; same quality at different sizes is possible H.265 is always 50% smaller Depends on encoder settings; poorly-configured H.265 can be worse than H.264 Hardware encoding is fine for quality Hardware encoders (NVENC, QuickSync) sacrifice quality for speed AI upscaling improves quality Upscaling adds artificial detail that wasn't in the source The Encoding Quality Hierarchy From most to least important: Encoder settings (CRF, preset, tuning) Encoder choice (x264/x265 vs. hardware encoders) Codec (H.265 vs. H.264 vs. VP9) Quick Reference: FFmpeg Commands Remux (Change Container, No Quality Loss)

MKV to MP4 (preserves all streams)

ffmpeg -i input.mkv -c copy output.mp4

MP4 to MKV

ffmpeg -i input.mp4 -c copy output.mkv Basic Encoding

Encode with x264, copy audio

ffmpeg -i input.mkv -c:a copy -c:v libx264 -preset slower -crf 20 output.mkv

Encode with x265

ffmpeg -i input.mkv -c:a copy -c:v libx265 -preset slower -crf 22 output.mkv Quality-Focused Encoding

High-quality x264 for animation

ffmpeg -i input.mkv -c:a copy -c:v libx264 -preset slower -crf 18 \ -x264-params bframes = 8 output.mkv

High-quality x265

ffmpeg -i input.mkv -c:a copy -c:v libx265 -preset slower -crf 20 \ -x265-params bframes = 8 output.mkv Encoding Settings Deep Dive CRF (Constant Rate Factor) CRF controls quality vs. file size tradeoff. Lower = higher quality, larger file. CRF Range Quality Level Typical Use 0 Lossless Archival, intermediate 15-18 Visually lossless High-quality archival 19-23 High quality General use, streaming 24-28 Medium quality Web, mobile 29+ Low quality Previews, thumbnails Note: CRF values aren't directly comparable between encoders. x265 CRF 22 ≈ x264 CRF 20. Preset Presets control encoding speed vs. compression efficiency. Preset Speed File Size Use When ultrafast Fastest Largest Live streaming fast Fast Large Quick transcodes medium Moderate Moderate Default slow Slow Smaller Quality-focused slower Very slow Even smaller Recommended for quality veryslow Extremely slow Smallest Maximum compression Recommendation: Use slower for quality-focused encoding. The difference between slower and veryslow is minimal for significant time cost. Tune Options Tune Best For film Live-action with film grain animation Cartoons, anime, flat areas grain Preserve film grain stillimage Slideshow, static content fastdecode Playback on weak devices

Animation tuning

ffmpeg -i input.mkv -c:v libx264 -preset slower -crf 20 -tune animation output.mkv Container-Specific Considerations MKV (Matroska) Pros: Supports virtually any codec Multiple audio/subtitle tracks Chapter markers Variable frame rate support Cons: Less compatible with some devices/software Some streaming services don't accept it MP4 Pros: Universal compatibility Web-friendly Hardware decoder support everywhere Cons: Limited subtitle format support Stricter codec requirements Constant frame rate expected Converting MKV to MP4 for Editing Software Some editing software requires constant frame rate MP4. Use this two-pass approach:

Step 1: Initial remux with timescale adjustment

ffmpeg -i input.mkv -c copy -video_track_timescale 24000 intermediate.mp4

Step 2: Fix timestamps

ffmpeg

-i

intermediate.mp4

-c

copy

\

-bsf:v

"setts=dts=1001round(DTS/1001):pts=1001round(PTS/1001)"

output.mp4

Color Space & Color Management

Understanding Color Metadata

Videos store colors in YCbCr format with metadata specifying:

Color matrix

How to convert YCbCr to RGB (BT.709, BT.601)

Color range

Limited (16-235) vs. Full (0-255)

Chroma location

Where color samples are positioned Common Issues Symptom Likely Cause Washed out colors Wrong color range (Limited treated as Full) Crushed blacks/blown whites Wrong color range (Full treated as Limited) Greenish/pinkish tint Wrong color matrix Colors look "off" after encode Mismatched color metadata Preserving Color Information

Explicitly preserve color metadata

ffmpeg -i input.mkv -c:v libx264 -preset slower -crf 20 \ -colorspace bt709 -color_primaries bt709 -color_trc bt709 output.mkv Hardsubbing (Burning In Subtitles) Using FFmpeg

Hardsub from external subtitle file

ffmpeg -i input.mkv -vf "subtitles=subs.ass" -c:v libx264 -preset slower -crf 20 output.mkv

Hardsub from embedded subtitle track

ffmpeg -i input.mkv -vf "subtitles=input.mkv:si=0" -c:v libx264 -preset slower -crf 20 output.mkv Using mpv (Better for Complex Subtitles) mpv handles complex ASS subtitles (styling, positioning) more accurately: mpv --no-config input.mkv -o output.mkv \ --audio = no \ --ovc = libx264 \ --ovcopts = preset = slower,crf = 20 ,bframes = 8 What to Avoid Tools Tool Problem Handbrake Unpredictable settings, hides important options Online converters Quality loss, privacy concerns "AI upscalers" Add fake detail, move further from source Windows built-in tools Poor quality, limited options Practices Practice Why It's Bad Unnecessary sharpening Adds artifacts, moves from source Upscaling to higher resolution Doesn't add real detail Multiple reencodes Quality loss compounds Using NVENC for quality Hardware encoders prioritize speed over quality Frame rate interpolation Adds fake frames with artifacts Recommended Tools Essential Tool Purpose ffmpeg Swiss army knife for video processing MediaInfo Inspect video properties and metadata mpv Superior media player, encoding support MKVToolNix GUI for MKV muxing operations Specialized Tool Purpose Aegisub Subtitle editing HandBrake Simple transcoding (use with caution) yt-dlp Download online videos Troubleshooting Video Won't Play Check codec support on target device Try remuxing to different container Verify file isn't corrupted: ffmpeg -v error -i file.mkv -f null - Colors Look Wrong After Encoding Compare color metadata: mediainfo input.mkv vs. mediainfo output.mkv Check color range (Limited vs. Full) Check color matrix (BT.709 vs. BT.601) Explicitly set color parameters in ffmpeg command File Size Too Large Increase CRF (e.g., 20 → 23) Use slower preset for better compression Consider x265 for better efficiency Check if you're unnecessarily encoding (remux instead) Encoding Takes Forever Use faster preset (but accept larger file) Check if hardware encoding is acceptable for your use case Ensure source isn't being decoded unnecessarily Audio/Video Out of Sync Check source file for sync issues first Use -async 1 for audio sync correction Try remuxing instead of reencoding Examples Archive a Blu-ray Rip ffmpeg -i input.mkv -c:a copy -c:v libx265 -preset slower -crf 18 \ -x265-params bframes = 8 output.mkv Prepare for YouTube Upload ffmpeg -i input.mkv -c:a aac -b:a 384k -c:v libx264 -preset slower -crf 18 \ -profile:v high -level 4.2 -pix_fmt yuv420p output.mp4 Quick Preview/Proxy ffmpeg -i input.mkv -c:a aac -b:a 128k -c:v libx264 -preset fast -crf 28 \ -vf scale = 640 :-2 output.mp4 Extract Audio Only

Copy audio stream (no re-encoding)

ffmpeg -i input.mkv -vn -c:a copy output.mka

Convert to MP3

ffmpeg -i input.mkv -vn -c:a libmp3lame -b:a 320k output.mp3 Trim Without Re-encoding

Trim from 1:00 to 2:30

ffmpeg -i input.mkv -ss 00:01:00 -to 00:02:30 -c copy output.mkv Resources FFmpeg Documentation FFmpeg Wiki x264 Settings Guide x265 Settings Guide MediaInfo mpv Manual