XF 1.2 twitch.tv in bb media sites


I have been able to add a media site for twitch live streams using the following:

Match URL: http://www.twitch.tv/{$id}
Embed HTML:
<object type="application/x-shockwave-flash" height="426" width="700" id="live_embed_player_flash" data="http://www.twitch.tv/widgets/live_embed_player.swf?channel={$id}" bgcolor="#000000">
<param name="allowFullScreen" value="true" />
<param name="allowScriptAccess" value="always" />
<param name="allowNetworking" value="all" />
<param name="movie" value="http://www.twitch.tv/widgets/live_embed_player.swf" />
<param name="flashvars" value="hostname=www.twitch.tv&channel={$id}&auto_play=false&start_volume=25" />
However, the code for embedding recordings is more complex as it requires both the channel name and the recording id to be parsed e.g. http://www.twitch.tv/anubis1055/b/474488829

is it possible to use an expression to match this url? I've tried myself but cant get my head around it.

This is the line in the embed code the channel needs to fill out:

<param name='flashvars' value='channel=EXAMPLE&auto_play=false&start_volume=25&chapter_id=EXAMPLE'></object>