Step by Step Windows 7 webM guide (with AviDemux and FFMPEG):
Setup:
1. Download and install Avidemux:
http://fixounet.free.fr/avidemux/
2. Download FFmpeg:
http://www.ffmpeg.org/download.html
3. Copy ffmpeg.exe to your home folder (e.g. "C:\Users\<Username> for Windows 7)
Conversion
1. Download source video (for youtube, you can use
http://keepvid.com/ )
2. Open video in Avidemux. Set begin point ("A") and end point ("B") for webm
3. Select MP4v2 Muxer in Output Window
4. File->Save video. Select your home folder and use .mp4 extension (e.g yourvideo.mp4)
5. open console (type "cmd" in start menu)
6. copy paste the following in the console (after changing parameters)
Code:
ffmpeg -i yourvideo.mp4 -vf scale=500:-1 -c:v libvpx -crf 10 -b:v 2M -c:a libvorbis yourvideo.webm
-vf scale sets the video resolution, 500 for 500 pixel width. Remove it if you want to keep original resolution
-crf is the quality setting, 10 default, 4 minimum (lower=better)
-b:v is the target bit rate, 2M for 2 Mbit per second (higher = better)
libvpx is the codec, libvpx-vp9 for VP9 instead of vp8
7. upload the .webm video to a .webm compatible hoster, e.g.
http://pomf.se/
8. copy paste the URL into your neogaf reply.