Encoding video for the web

encoding-video.md

Encoding Video

Installing

Install FFmpeg with homebrew. You'll need to install it with a couple flags for webm and the AAC audio codec.

brew install ffmpeg --with-libvpx --with-libvorbis --with-fdk-aac --with-opus

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

brew reinstall ffmpeg --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 -vcodec h264 -acodec 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 -vcodec libx264 -pix_fmt yuv420p -profile:v baseline -level 3 output.mp4

Convert to WebM

VP8

libvpx is the VP8 video encoder for ​WebM. FFmpeg and WebM Encoding Guide will walk you through webm specifics.

In this example, input.mov is converted to output.webm with a constant rate factor of 10 (lower is higher quality) at a bitrate of 1M. Changing the bitrate to something lower (e.g. 700K) will result in lower file sizes and lower quality. If your video does not have audio, you may leave off the -acodec libvorbis part.

ffmpeg -i input.mov -vcodec libvpx -qmin 0 -qmax 50 -crf 10 -b:v 1M -acodec libvorbis output.webm

VP9

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

Here's an example from the FFmpeg guide:

ffmpeg -i input.mov -vcodec libvpx-vp9 -b:v 1M -acodec 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

Support

As of January 2015, all major browsers support MP4.

Data current as of May 2019. Sources:

• jwplayer's research
• caniuse for AV1
• caniuse for MPEG-4/H.264
• caniuse for HEVC/H.265
• caniuse for WebM

Browser	AV1	H264	H265	VP8	VP9	AAC	MP3	VORBIS	OPUS
Chrome for Desktop	70	30	-	30	30	30	30	30	33
Chrome for Android	-	30	-	30	30	30	30	30	-
IE	-	9	101	-	-	9	9	-	-
IE Mobile	-	10	-	-	-	10	10	-	-
Edge	75	12	121	-	142	12	12	-	14
Firefox for Desktop	67	22	-	20	28	22	22	20	20
Firefox for Android	-	20	-	20	28	20	20	20	20
Safari for Mac	-	3	113	-	-	3	3	-	-
Safari for iOS	-	3	113	-	-	3	3	-	-
Opera for Desktop	57	25	-	11	16	-	-	11	12
Android Stock Browser	-	2.3	-	4.0	5	2.3	2.3	4.0	-

Notes

1. Supported only for devices with hardware support.
2. Edge 14+ has partial support for VP9
3. Supported only on macOS High Sierra and onwards.

Recommended markup

Since all browsers support MP4, we can use WebM's VP9 codec for modern browsers and fall back to MP4s for the rest.

<video>
  <source src="path/to/video.webm" type="video/webm; codecs=vp9,vorbis">
  <source src="path/to/video.mp4" type="video/mp4">
</video>

Creating thumbnail images from the video

Here's their guide. Output a single frame from the video.

ffmpeg -i input.mp4 -ss 00:00:14.435 -vframes 1 out.png

Output one image every second as a jpg.

ffmpeg -i input.mp4 -vf fps=1 out%3d.jpg

Reversing a video

FFmpeg now has a reverse filter. Usage: (source from this video.stackexchange answer)

For video only:

ffmpeg -i input.mp4 -vf reverse reversed.mp4

For audio and video:

ffmpeg -i input.mp4 -vf reverse -af areverse reversed.mp4

This filter buffers the entire clip. For larger files, segment the file, reverse each segment and then concat the reversed segments.

Funny results I have to say. I have 1m 19s animated video. Original MP4 1080p file has 108MiB.

MP4 takes few seconds and resulting file is 14.2MiB
VP8 takes around 1m and file is 10MiB
VP9 takes around 2m and file is 15.7MiB
VP9 (google recomended) takes around hour and file is 13.9MiB

Can't see any benefits of VP9 or it's animated video same special case?
-- @zajca

I shared the same sentiment when I started pasting these command snippets into my terminal. Then I realise, these command snippets vary in output options, in terms of their encoding speed, output resolution, frame rate, bitrate and quality.

So I have decided to make a few things constant.

• preset medium, unrestricted threads, same speed
• resolution 720p
• frame rate 24
• fixed average bitrate 500 / 1000

And here is my result and my opinion

Codec	Average bitrate	Size	Time taken (s)	My quality rating
x264	1000k	3.705 mb	Video duration (s) / 5	6.5 / 10
x264	500k	1.857 mb	Video duration (s) / 5	4 / 10
vp8	500k	1.909 mb	Video duration (s) / 1.5	6.5 / 10
vp9	500k	1.661 mb	Video duration (s) / 0.07	7 / 10

In my context,

• given the same compression settings, vp9 seems to have a better visual quality compared to vp8.
• vp9 / vp8 output seems to output same visual quality with half the file size compared to x264

Expand for commands

ffmpeg -y -an -i input.mov \
  -pass 1 -b:v 500K \
  -threads 0 -speed 4 -preset medium \
  -vf scale=-1:720 -r 24 \
  -c:v libx264 \
  -pix_fmt yuv420p -profile:v baseline -level 3.0 -movflags +faststart \
  -f mp4 \
  /dev/null
ffmpeg -y -an -i input.mov \
  -pass 2 -b:v 500K \
  -threads 0 -speed 0 -preset medium \
  -vf scale=-1:720 -r 24 \
  -c:v libx264 \
  -pix_fmt yuv420p -profile:v baseline -level 3.0 -movflags +faststart \
  -f mp4 \
  output-x264-500k.mp4



ffmpeg -y -an -i input.mov \
  -pass 1 -b:v 1000K \
  -threads 0 -speed 4 -preset medium \
  -vf scale=-1:720 -r 24 \
  -c:v libx264 \
  -pix_fmt yuv420p -profile:v baseline -level 3.0 -movflags +faststart \
  -f mp4 \
  /dev/null
ffmpeg -y -an -i input.mov \
  -pass 2 -b:v 1000K \
  -threads 0 -speed 0 -preset medium \
  -vf scale=-1:720 -r 24 \
  -c:v libx264 \
  -pix_fmt yuv420p -profile:v baseline -level 3.0 -movflags +faststart \
  -f mp4 \
  output-x264-1000k.mp4



ffmpeg -y -an -i input.mov \
  -pass 1 -b:v 500K \
  -threads 0 -speed 4 -preset medium \
  -vf scale=-1:720 -r 24 \
  -c:v libvpx \
  -tile-columns 0 -frame-parallel 0 -auto-alt-ref 1 -lag-in-frames 25 -g 9999 -aq-mode 0 \
  -f webm \
  /dev/null
ffmpeg -y -an -i input.mov \
  -pass 2 -b:v 500K \
  -threads 0 -speed 0 -preset medium \
  -vf scale=-1:720 -r 24 \
  -c:v libvpx \
  -tile-columns 0 -frame-parallel 0 -auto-alt-ref 1 -lag-in-frames 25 -g 9999 -aq-mode 0 \
  -f webm \
  output-vp8-500k.webm



ffmpeg -y -an -i input.mov \
  -pass 1 -b:v 500K \
  -threads 0 -speed 4 -preset medium \
  -vf scale=-1:720 -r 24 \
  -c:v libvpx-vp9 \
  -tile-columns 0 -frame-parallel 0 -auto-alt-ref 1 -lag-in-frames 25 -g 9999 -aq-mode 0 \
  -f webm \
  /dev/null
ffmpeg -y -an -i input.mov \
  -pass 2 -b:v 500K \
  -threads 0 -speed 0 -preset medium \
  -vf scale=-1:720 -r 24 \
  -c:v libvpx-vp9 \
  -tile-columns 0 -frame-parallel 0 -auto-alt-ref 1 -lag-in-frames 25 -g 9999 -aq-mode 0 \
  -f webm \
  output-vp9-500k.webm

Thank you @Vestride for a very nice writeup!

Thank you so much for the tutorial. I'm building a streaming plattform and I was wondering if you can convert uploaded videos to mp4 (for browser support) using ffmpeg. It works fine but one big problem is the speed and propably quality (not tested). But if you convert to webm, you'll loose all the quality.

Which codec to use with opencv videowriter() when deploying to heroku, because majority of codec are not working on deploying my flask app. I have added the ffmpeg buildpack as well, but still the error shows up.

amazeballs! thanks

Thanks for posting, this helped my solve my issues. I ran into this problem quite a bit with moviepy and webm/H.264 encoded videos. A set of moviepy write_videofile params that worked for all browsers was:

        result.write_videofile(f"{out_filename}",
                               fps=25,
                               codec='libx264',
                               bitrate='5000k',
                               preset='superfast',
                               logger=None,
                               temp_audiofile=tmp_audio_file,
                               audio_codec="aac",
                               ffmpeg_params=["-vf","scale=1024:-2","-pix_fmt","yuv420p","-level","3"]
                               )

Setting scale was needed to ensure video width/height we divisible by 2.

Note that the method specified to install FFmpeg with options no longer works; example error "Error: invalid option: --with-libvpx"

Any solution/workaround?

Edit:

With the latest homebrew (brew update), it seems that these flags no longer exist for ffmpeg and all the "--with-FOO" options listed here are installed by default. I just tried it out and all the builds appear to work!

brew install ffmpeg
==> Installing dependencies for ffmpeg: aom, frei0r, fribidi, pcre, glib, pixman, cairo, graphite2, harfbuzz, libass, libbluray, libogg, libvorbis, libvpx, opencore-amr, opus, rtmpdump, flac, libsndfile, libsamplerate, rubberband, sdl2, snappy, speex, giflib, webp, leptonica, tesseract, theora, x264 and x265
…

Or you can just upload to youtube, let him process the video then download 🐸🐸🐸

Will x265 be supported better in the future? I am currently transcoding all my ancient .mpg files
recorded in the 1990s or before to x265. Size reduction is great, but if I can not view it in the
browser then this is not so good - I need some of these videos for elderly relatives who are
still alive but may not be alive in the next some years ...

Also, can someone update this? Right now it has "Data current as of May 2019"; or perhaps
someone can link in here to a more recent comparison? I found this here via StackOverflow
links actually.