Game streaming site Twitch has started muting the audio of any video that is detected to include unauthorized audio—which is to say, any video that includes any reasonably mainstream background music.

While Twitch's main purpose is to be a platform for live game streams, which are, for the time being, unaffected, it also has a substantial library of archived broadcasts and highlight clips. These archives and highlights will have their audio muted if they're detected to contain any music owned or controlled by clients of Audible Magic, a music matching and recognition service already used by Vimeo, Facebook, and others. Twitch archives are stored in 30-minute chunks, and if any infringing audio is found in a chunk, the entirety of that section will be muted.

Earlier today, the company announced that full stream archival is being removed, but highlight clips will remain.

The impact of this is far-reaching, with an enormous quantity of Twitch's video on demand (VOD) content being muted. Twitch streamers routinely listen to music while streaming, and e-sports broadcasts often play music between matches. All are now silent. This includes high-profile events such as Valve's Dota 2 tournament, The International 4, and Twitch's own weekly gaming show, Twitch Weekly. Twitch says that even in-game audio will trigger the muting if it is detected by Audible Magic's system. This includes not only games, such as the Grand Theft Auto series, that license various songs, but also music written solely for those games, with videos of games like Mike Tyson's Punch Out being muted.

The new policy comes as rumors about Twitch and Google continue to swirl around. The advertising giant is believed to be in negotiations to buy Twitch for $1 billion. While neither company has made the sale official, evidence continues to mount that Twitch is streamlining and tidying up its operations to make it more attractive to a buyer. Yesterday Justin.tv, the streaming site that begat Twitch, announced its immediate closure, leaving Twitch as its sole streaming service.

Getting its copyright house in order is a logical next step—while the RIAA would likely see little gain from suing Twitch, suing a Google-owned Twitch could be a whole lot more lucrative.

One slightly surprising aspect is that Twitch is using Audible Magic's service for copyright enforcement; if Google is indeed to buy the company, one might have expected Twitch to switch to YouTube's Content ID system instead.