ffmpeg code snippets

ffmpeg-helper.md

Encoding Video

Installing

Install FFmpeg with homebrew. All codecs.

brew install ffmpeg --with-fdk-aac --with-ffplay --with-freetype --with-libass --with-libquvi --with-libvorbis --with-libvpx --with-opus --with-x265

If you already have ffmpeg installed, but not with the other libraries, use the reinstall command.

brew reinstall ffmpeg --with-libvpx --with-opus

FFmpeg options. The -c:v option is an alias for -vcodec and -c:a is an alias for -acodec. -crf is Constant Rate Factor.

Constant Rate Factor

This method allows the encoder to attempt to achieve a certain output quality for the whole file when output file size is of less importance. This provides maximum compression efficiency with a single pass. Each frame gets the bitrate it needs to keep the requested quality level. The downside is that you can't tell it to get a specific filesize or not go over a specific size or bitrate.

Convert to MP4

When converting to an MP4, you want to use the h264 video codec and the aac audio codec because IE11 and earlier only support this combination. The FFmpeg and H.264 Encoding Guide can walk you through some of the H.264 specific options.

ffmpeg -i input.mov -c:v h264 -c:a aac -strict -2 output.mp4

For maximum compatibility, use the profile option. This may, however, increase the bit rate quite a bit. You can disable the audio stream with the -an option. -pix_fmt yuv420p is for Apple Quicktime support.

In this example, input.mov is converted to output.mp4 with maximum compatibility, with Quicktime support, and without an audio stream.

ffmpeg -an -i input.mov -c:v libx264 -pix_fmt yuv420p -profile:v baseline -level 3 output.mp4

Convert to WebM

VP9

VP9 can encode videos at half the file size 👏 Check out Google's VP9 encoding guide for the recommend settings or the FFmpeg VP9 guide.

Here's an example from the FFmpeg guide:

ffmpeg -i input.mov -c:v libvpx-vp9 -b:v 1M -c:a libvorbis output.webm

And here's Google's "Best Quality (Slowest) Recommended Settings". You need to run the first line(s). It will create a log file (and warn you the out.webm is empty). On the second pass, the video will be output.

ffmpeg -i <source> -c:v libvpx-vp9 -pass 1 -b:v 1000K -threads 1 -speed 4 \
  -tile-columns 0 -frame-parallel 0 -auto-alt-ref 1 -lag-in-frames 25 \
  -g 9999 -aq-mode 0 -an -f webm /dev/null


ffmpeg -i <source> -c:v libvpx-vp9 -pass 2 -b:v 1000K -threads 1 -speed 0 \
  -tile-columns 0 -frame-parallel 0 -auto-alt-ref 1 -lag-in-frames 25 \
  -g 9999 -aq-mode 0 -c:a libopus -b:a 64k -f webm out.webm

Using max threads for a little faster encoding. (Also almost lossless video)

• -threads 0 only uses 1 core, -threads 8 uses 2 cores, and -threads 16 uses 4 cores.

ffmpeg -i input.mp4 -c:v libvpx-vp9 -crf 10 -threads 16 -b:v 5000k -c:a libvorbis output.webm

Referenced from Vestride