A little YouTube video quality problem is puzzling me right now, if I upload a 480p video I get what looks like artifacts produced by a bad de-interlacing algorithm:
If I however scale the video to 1280x1024 before the upload, the result in 480p on YouTube looks fine and close to the original 480p data:
Searching around on the net hasn't brought any clues so far. The original video was produced with HandBrake and matches from what I can tell YouTubes recommended video formats.
Uploading the video as 360p directly doesn't seem to have this problem, but that of course means lower quality then 480p.
Update: I still have no idea on the cause of the pixelation or how to fix it without reencoding, a rencoding of the video into flv however seems to work:
mencoder inputvideo.mkv -oac mp3lame -ovc lavc -lavcopts vcodec=flv:vbitrate=500:trell:v4mv:mv0:mbd=2:cbp:aic:cmp=3:subcmp=3 -o outputvideo.flv
Update: The problem seems to be h.264/x264 specific, Using MPEG4 as codec works as well:
mencoder raw.avi -o mplayer-mpeg4.avi -oac mp3lame -ovc lavc -lavcopts vcodec=mpeg4:mbd=1:vbitrate=800
Update: I solved the problem now with the MPEG4 codec for those of my videos that had that issue. While doing so I ran into the problem that Youtube doesn't offer import/export of annotations, thus no way to copy over annotations from the badly encoded video to the cleaned up one, luckily there is a workaround. This video explains how one can import and export annotations. Short summary, use
http://www.google.com/reviews/y/read2?video_id=YOUR_VIDEO_ID_HERE to get an xml of your annotation and then the Firefox Tamper Data Add-On to fudge your annotations into a POST request.
Update: Two questions on the YouTube help forum referencing this problem: