Comment 28 for bug 323649

That depends on you. You can wait until its in the repos, or do it yourself. I prefer to have an official version from the repos together with the patched version (in case I screw something in the source code).

The file is in totem-2.30.2.tar.bz2 which can be downloaded from the main totem page.
Its located in: <your unpacked folder>/src/plugins/youtube/totem-youtube.c

These are the lines used to construct the movie uri:

529: video_uri_string = g_string_new ("http://www.youtube.com/get_video?video_id=");
530: g_string_append_uri_escaped (video_uri_string, video_id, NULL, TRUE);
531: g_string_append (video_uri_string, "&t=");
532: g_string_append_uri_escaped (video_uri_string, t_param, NULL, TRUE);
533: g_string_append (video_uri_string, fmt_param);

Youtube now requires a mendatory "&asv=" parameter in the uri, so you just need to add one line after the above code:

534: g_string_append (video_uri_string, "&asv=");