WebM

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WebM (file extension .webm) is a video file format developed by  Google, based upon the  Matroska (MKV) container format. WebM was originally designed to be used on webpages to save bandwidth, but it also has some benefits when it comes to video games and many other applications.

The biggest benefit of WebM over Bink (or AVI) for games is that of file size; a WebM video will be significantly smaller than that of a similar-quality Bink file as WebM has better compression than Bink. For example, the installation size of Hunt Down the Freeman decreased by 5.7 GB when switching its FMV cutscenes from Bink to WebM^[1]. Furthermore, WebM is much more common and easier to make than the Bink file format, as Bink requires the RAD Video Tools software that only takes AVI files (MP4 initially required QuickTime until the requirement was eventually removed as QuickTime for Windows is no longer supported by Apple).

WebM is supported in the following games, engines, and engine branches:

	Video codecs			Audio codecs
Implementation	VP8	VP9	AV1	Vorbis	Opus
Source 2 ( tested)	Yes	Yes	No	Yes**	Yes**
GoldSrc (since 25th anniversary update; intro video only)	Yes	Yes	No	Yes*	No
Counter-Strike: Global Offensive (since 2018 Panorama update)	Yes	Yes	No	Yes***	No
Team Fortress 2 (since April 18, 2024/64-bit update)	Yes	Yes	No	Yes	No
Strata Source	Yes	Yes	No	Yes	No
WebM Video Services for (used by Hunt Down the Freeman)	Yes	Yes	No	Yes	Yes

*Audio is read, but muted. <moddir>/sound/ui/valve_sound.wav is used instead.

**Audio is read, but muted. (only in ) If the video was unable to play due to incompatible codecs or other codecs issue, then part of the intro sounds (sounds/ui/logo_startup.vsnd_c, which is played separately) will not play or likely be played in lower volume.

***Sometimes audio plays in slower speed and lower pitch.

To convert a 1080p MP4 file to a WebM that will reliably play in the the above games and have reasonable quality and encoding speed, use the following  ffmpeg script:

ffmpeg -i input.mp4 -acodec libvorbis -ab 128k -vb 0 -crf 31 output.webm

• To increase audio quality, increase -ab.
• To increase video quality, reduce -crf. Lower values may be necessary for higher and lower resolutions to reduce macroblocking artefacts.

References

References
1. Hunt Down The Freeman - July blog: where we're at + looking for team members! - Steam News Bink video is replaced with webm (like CSGO and Source 2) and has successfully freed up 5.7GB of space

External links

•  WebM on Wikipedia