ffmpeg-post-production

FFmpeg Post-Production

Finish and deliver video with commands that are checked against the FFmpeg docs, not remembered from a forum.

When to Use

• Trimming, joining, or reframing renders and screen recordings
• Normalizing audio loudness before publishing
• Adding captions (soft track or burned in)
• Producing web/social deliverables and thumbnails from a master

When NOT to Use

• Creating motion graphics from scratch: use Remotion or HyperFrames (see video-production-pipeline)
• Generating captions from speech: see captions-and-transcription (this skill only applies them)

Workflow

Step 1: Inspect Before You Touch

ffprobe -v error -show_entries format=duration:stream=index,codec_type,codec_name,width,height,r_frame_rate,sample_rate \
  -of default=noprint_wrappers=1 input.mp4

Check the filters you plan to use exist in this build. Caption burn-in needs a build configured with --enable-libass; some packaged builds omit it.

ffmpeg -hide_banner -filters | grep -E ' (subtitles|ass|loudnorm|thumbnail|xfade) '

Always write to a new output file. Never overwrite the source; keep the master untouched.

Step 2: Trim

# Frame-accurate: re-encode. -ss before -i seeks fast; with transcoding, accurate seek is the default.
ffmpeg -ss 00:00:02 -to 00:00:05 -i input.mp4 -c:v libx264 -crf 18 -preset medium -c:a aac clip.mp4

# Fast, no quality loss, but cuts land on keyframes (the clip may start early or run long).
ffmpeg -ss 2 -i input.mp4 -t 3 -c copy clip_copy.mp4

-to and -t are mutually exclusive; -t wins if both are given. Use stream copy only when keyframe-accurate cuts are acceptable.

Step 3: Concatenate

Concat demuxer, for files with identical streams (same codecs, resolution, time base):

printf "file 'intro.mp4'\nfile 'main.mp4'\nfile 'outro.mp4'\n" > list.txt
ffmpeg -f concat -safe 0 -i list.txt -c copy joined.mp4

-safe 0 allows absolute or unusual paths in the list; omit it when all paths are simple relative names. If the inputs differ (different encoders or sizes), re-encode them to a common format first, or use a crossfade (Step 5).