WebM

WebM support is (hopefully) the newest addition to 4chan. This wiki page is meant to serve as an instructional tool to help you get started converting your content to WebM for posting.

WebM {is being, was} tested in these threads:

• https://rbt.asia/g/thread/S41184007
• https://rbt.asia/g/thread/S41183707
• https://rbt.asia/g/thread/S41178861
• https://rbt.asia/g/thread/S41190521

... and on a few /jp/ threads.

Converting with ffmpeg

Note: avconv and ffmpeg are not entirely drop-in replacements. Make sure you know which one you are using.

Linux and OS X Scripts

If you're using OS X or Linux, you probably know how to save and execute these scripts already, but here's a quick overview:

1. Create a file, such as ~/bin/my_script.sh
2. Copy and paste the code into this file with your favorite editor.
3. Open a shell. Run the command chmod +x ~/bin/my_script.sh
4. The script can now be called as ~/bin/my_script.sh some_file.type or if you have your PATH set correctly, my_script.sh some_file.type

Basic .gif to .webm

#!/bin/bash
out=${1%%.gif}.webm
ffmpeg -i $1 -c:v libvpx -crf 32 -b:v 300K $out

Basic video to .webm

#!/bin/bash
ffmpeg -i $1 -c:v libvpx -an $1.webm

Windows

After installing ffmpeg/avconv, most of these commands can be saved as .bat files and placed in the folder of the media file you wish to work with. Or you can just run them from the command prompt, assuming you have your PATH set correctly.

Basic .gif to .webm

Basic video to .webm

ffmpeg.exe -i "C:\Users\Anon\Input_File.mkv" -ss 30 -t 15 -codec:v vp8 -an "C:\Users\Anon\Output_File.webm"

Heftier video to .webm

@echo off
rem about 3megabyte in bit 3*1024*1024*8*0.95
set /A MAXSIZE=23907532
set WIDTH=720
ffmpeg -i %1 2> webm.tmp
for /F "tokens=1,2,3,4,5,6 delims=:., " %%i in (webm.tmp) do (
    if "%%i"=="Duration" call :calcLength %%j %%k %%l %%m
)
del webm.tmp
SET /a BITRATE=%MAXSIZE%/%VSECONDS%
ffmpeg -y -i %1 -threads 0 -sn -an -c:v libvpx -b:v %BITRATE% -vf scale=-1:%WIDTH% -quality best -cpu-used 0 -slices 8 -auto-alt-ref 1 -f webm -pass 1 NUL
ffmpeg -y -i %1 -threads 0 -sn -an -c:v libvpx -b:v %BITRATE% -vf scale=-1:%WIDTH% -quality best -cpu-used 0 -slices 8 -auto-alt-ref 1 -f webm -pass 2 "%~n1.webm"
del ffmpeg2pass-0.log > NUL
goto :EOF
:calcLength
FOR /F "tokens=* delims=0" %%A IN ("%3") DO SET /A s=%%A
FOR /F "tokens=* delims=0" %%A IN ("%2") DO SET /A s=s+%%A*60
FOR /F "tokens=* delims=0" %%A IN ("%1") DO SET /A s=s+%%A*60*60
set /A VSECONDS=s

Other WebM Creation

Please see Reccomended_software for a list of good software for handling video files such as WebM.

Sources and Resources

1. https://trac.ffmpeg.org/wiki/vpxEncodingGuide
2. WebM of a WebM tutorial: https://rbt.asia/boards/g/img/0411/75/1396646705233.webm