Yes! It's so hard to download from those sites. Most of those "download from tudou or youku" sites either don't work or force you to download some video downloader filled with malware.
Hi~There's a feasible way to solve your problems. You can try this Chinese software called big-rat（硕鼠 ）,http://www.flvcd.com/. You can easily download videos from Tudou, Youku and many other Chinese sites.
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Tudou, Youku