FFmpeg: The Ultimate Cross-Platform Video Tool

I’ve always maintained that only cross-platform software merits long-term commitment. Final Cut Pro is indeed formidable, and Adobe’s suite is undeniably capable, but neither runs natively on every operating system. Once you’ve grown accustomed to them, you’ve effectively tied yourself to the systems they run on. Departing from a particular platform means abandoning these familiar tools, significantly increasing your sunk costs.

But fear not, FFmpeg covers our asses.

I started using it by processing some simple tasks, such as trimming the duration of video or audio clips, extracting segments, merging multiple clips, changing the format of videos (e.g. .mkv to .mp4) to make them more compatible with different devices, re-encoding video and audio (e.g. H.264 to HEVC or Opus to AAC), compressing videos, changing their resolution and burning subtitles into videos.

These tasks are a daily driver for me at certain times, but they are not worth processing by launching a large app like Final Cut Pro. After some time of learning and hands-on practice, I’ve compiled a list of frequently used commands for reference.

1. Basic Trimming

Trimming a video without re-encoding is extremely fast as it simply copies the compressed data without decoding.

Keep everything from 10 minutes onwards:

ffmpeg -t 00:10:00 -i input.mp4 -c copy output.mp4

Extract a 20-minute segment starting from 10:00:

ffmpeg -ss 00:10:00 -i input.mp4 -t 00:20:00 -c copy output.mp4

Trim the first 20 minutes:

ffmpeg -ss 00:20:00 -i input.mp4 -c copy output.mp4

2. Merging and Concatenation

If you have multiple clips with the same parameters (resolution, codec, etc.), you can merge them using the concat demuxer.

Merge clips listed in merge.txt:

ffmpeg -f concat -safe 0 -i merge.txt -c copy output.mp4

merge.txt should contain lines formatted as file 'input.mp4'. You can download a template here.

Merge clips without a text file (Shell inline list):

ffmpeg -f concat -safe 0 -i <(printf "file '%s'\n" input1.mp4 input2.mp4) -c copy output.mp4

On macOS or Linux (zsh/bash), process substitution (<(...)) feeds the file list directly from memory. This saves you from creating a physical merge.txt file on disk while keeping the blazing-fast, lossless stream copy (-c copy). All clips must still have identical codecs and parameters.

Merge clips with different parameters (concat filter):

ffmpeg -i input1.mp4 -i input2.mp4 -filter_complex \
"[0:v][0:a][1:v][1:a]concat=n=2:v=1:a=1[v][a]" \
-map "[v]" -map "[a]" output.mp4

Unlike the concat demuxer, the concat filter decodes and re-encodes the streams. This eliminates the need for an external file and seamlessly handles clips with different resolutions, framerates, or codecs, though it will take longer to encode.

Side-by-side comparison with audio (1080p, High Quality):

ffmpeg -i input1.mov -i input2.mp4 -filter_complex \
"[0:v]fps=60,scale=-2:1080[v0]; \
 [1:v]fps=60,scale=-2:1080[v1]; \
 [v0][v1]hstack=inputs=2[v]" \
-map "[v]" -map 1:a -c:v libx264 -crf 19 -preset medium -c:a aac -b:a 129k -pix_fmt yuv420p -shortest output_side_by_side_hq.mp4

Scales both inputs to 1080p height and places them side-by-side horizontally using hstack. It retains the audio track from the second video (-map 1:a), balances high quality with reasonable file size (-crf 19), and trims output to the shorter video (-shortest).

Side-by-side comparison for desktop / text clarity (1800p, Near-lossless):

ffmpeg -i input1.mov -i input2.mp4 -filter_complex \
"[0:v]fps=60,scale=-2:1800:flags=lanczos[v0]; \
 [1:v]fps=60,scale=-2:1800:flags=lanczos[v1]; \
 [v0][v1]hstack=inputs=2[v]" \
-map "[v]" -an \
-c:v libx264 -crf 12 -preset veryslow \
-x264-params "no-deblock=1:aq-mode=3:qcomp=0.8" \
-pix_fmt yuv420p -shortest output_ultra.mp4

Ideal for screen recording comparisons where text and UI sharpness matter. It scales to 1800p using the sharper lanczos algorithm, strips audio (-an), and disables in-loop deblocking (no-deblock=1) with -crf 12 to prevent fine UI details and fonts from being smoothed out.

3. Encoding for Compatibility

Sometimes you need to ensure a video plays everywhere (QuickTime, Safari, iOS, smart TVs, and web browsers) by using standard H.264 settings with 8-bit YUV 4:2:0 chroma subsampling.

High-quality H.264 re-encode for universal playback and storage:

ffmpeg -i input.mp4 -c:v libx264 -crf 18 -preset veryslow -pix_fmt yuv420p -c:a aac -b:a 129k -tag:v avc1 output.mp4

4. Burning Subtitles (Hardsubs)

Burning subtitles directly into the video stream ensures they show up on any player.

Basic subtitle burn-in:

ffmpeg -i input.mp4 -vf "subtitles=subtitle.srt" -c:a copy output.mp4

Burn subtitles with spaces in the filename (Best Practice):

ffmpeg -i input.mkv -vf "subtitles='my subtitles.srt'" -c:a copy output.mkv

Burn VTT subtitles with a specific font (Songti SC):

ffmpeg -i input.mp4 -vf "subtitles=subtitle.vtt:force_style='FontName=Songti SC'" -c:v libx264 -crf 18 -preset veryslow -pix_fmt yuv420p -c:a aac -b:a 129k -tag:v avc1 output.mp4

5. Format Conversion and Optimization

Converting between formats like WebM to MP4 or using modern codecs like HEVC (H.265).

Compress a video to 720p MP4 (H.264) with audio re-encoding:

ffmpeg -i input.mp4 -vf scale=1280:720 -c:v libx264 -crf 23 -preset slow -pix_fmt yuv420p -c:a aac -b:a 129k -tag:v avc1 output.mp4

Compress a video to 10-bit 1080p MP4 (H.265) with original audio codec:

ffmpeg -i input.mp4 -vf scale=1920:1080 -c:v libx265 -crf 28 -preset slow -pix_fmt yuv420p10le -c:a copy -tag:v hvc1 output.mp4

6. macOS Hardware Acceleration (VideoToolbox)

If you’re on a Mac, using videotoolbox will significantly speed up the encoding process and save battery.

Fast H.264 and Apple native AAC re-encoding:

ffmpeg -hwaccel videotoolbox -i input.webm -c:v h264_videotoolbox -b:v 5000k -c:a aac_at -q:a 0 -tag:v avc1 output.mp4

Fast 10-bit HEVC (H.265) and Apple native AAC re-encoding:

ffmpeg -hwaccel videotoolbox -i input.webm -c:v hevc_videotoolbox -b:v 3000k -pix_fmt p010le -c:a aac_at -q:a 0 -tag:v hvc1 output.mp4

HEVC and aac_at with Burned Subtitles:

ffmpeg -i input.webm -vf subtitles=subtitle.vtt -c:v hevc_videotoolbox -b:v 2500k -pix_fmt p010le -c:a aac_at -q:a 0 -tag:v hvc1 output.mp4

H.264 with Burned Subtitles (Custom Font for Chinese):

ffmpeg -i input.webm -vf "subtitles=subtitle.vtt:force_style='FontName=Songti SC'" -c:v h264_videotoolbox -b:v 4000k -c:a aac_at -q:a 0 -tag:v avc1 output.mp4

HEVC with Burned Subtitles (Custom Font for Chinese):

ffmpeg -i input.webm -vf "subtitles=subtitle.vtt:force_style='FontName=Songti SC'" -c:v hevc_videotoolbox -pix_fmt p010le -b:v 2500k -c:a aac_at -q:a 0 -tag:v hvc1 output.mp4

7. Audio Extraction

Extracting high-quality audio from video files.

Extract audio to M4A without re-encoding (Fastest, Original Quality):

ffmpeg -i input.mp4 -vn -c:a copy output.m4a

Extract audio to M4A using libfdk_aac re-encoding (VBR scale: 1 - 5, 5 is the highest quality):

ffmpeg -i input.mp4 -vn -c:a libfdk_aac -vbr 5 output.m4a

Extract audio to M4A using aac_at re-encoding (macOS Native, 0 - 14, 0 is the highest quality):

ffmpeg -i input.mp4 -vn -c:a aac_at -q:a 0 output.m4a

Advice for macOS Users (Homebrew & Audio Encoders)

If you find that some of these commands fit your requirements, or if you’re interested in exploring more of what FFmpeg has to offer and are ready to install it on your Mac, here is some practical guidance.

First, an important clarification: you do not need third-party taps just to get high-quality AAC audio on macOS. Standard Homebrew FFmpeg (brew install ffmpeg) already has Apple’s native aac_at (AudioToolbox AAC) enabled out of the box. aac_at is widely regarded as one of the best AAC encoders available, rivaling or exceeding libfdk_aac without compiling anything from source.

However, if you want non-free libraries like Fraunhofer’s FDK AAC (libfdk_aac) for cross-platform script parity, or other optional features not included in core Homebrew even with brew install ffmpeg-full, you can use the homebrew-ffmpeg/homebrew-ffmpeg tap. According to the official FFmpeg macOS compilation guide:

Since v2.0, Homebrew does not offer options for its core formulae anymore. Users who want to build ffmpeg with additional libraries (including non-free ones) need to use so-called taps from third party repositories. These repositories are not maintained by Homebrew.

To install FFmpeg with custom options via the tap:

brew tap homebrew-ffmpeg/ffmpeg
brew install homebrew-ffmpeg/ffmpeg/ffmpeg --with-<option1> --with-<option2> ...

For example, to build with libfdk_aac:

brew install homebrew-ffmpeg/ffmpeg/ffmpeg --with-libfdk-aac

Troubleshooting

While building with custom options increases flexibility, it comes with a maintenance cost. After running brew upgrade, you may occasionally notice your custom FFmpeg build breaking with dynamic linker dyld errors. This happens when Homebrew updates a shared library dependency (such as x264 or openssl) to a new version path, leaving your custom-compiled FFmpeg linked to the old, deleted path.

Fortunately, it is easy to repair. Simply reinstall FFmpeg to recompile it against the updated libraries:

brew reinstall homebrew-ffmpeg/ffmpeg/ffmpeg

Homebrew remembers the --with-* options you originally selected and reapplies them during the reinstall.

In the next blog, I’ll introduce another free software that can cooperate with FFmpeg and make it even stronger.