curl - 为什么 Curl 会忽略给定的范围？

Question

我需要使用 Curl 下载 Youtube 视频的特定部分。 (假设我想下载前 2MB)我在 Curl 中使用 -r 开关来实现这一点。它适用于非 YouTube 链接，但 Youtube 链接会忽略我用 -r 指定的范围。 Curl 下载整个视频文件，而不是下载我想要的 block 。我该怎么做？
提前致谢!

(我使用的示例代码:)

curl --cookie "VISITOR_INFO1_LIVE=EIBGUtRnRx4; demographics=d9e6a6b806922b989c443b57cc40cf59e3QDAAAAYWdlaRQAAAB0BgAAAGdlbmRlcnQBAAAAbTA=; s_tempdata-336183159=ei=xBC_UeOJLs6hkgXB7oGwDw&ved=CDcQvxs; s_tempdata-3430648675=ei=xBC_UeOJLs6hkgXB7oGwDw&ved=CEwQvxs; s_tempdata-877158463=ei=xBC_UeOJLs6hkgXB7oGwDw&ved=CF8Qvxs; s_tempdata-2333910030=ei=xBC_UeOJLs6hkgXB7oGwDw&ved=CHsQvxs; s_tempdata-3498387738=ei=xBC_UeOJLs6hkgXB7oGwDw&ved=CDIQvxs; s_tempdata-106278690=ved=CFcQvxs&ei=Q9LCUfqrJMK0kgX3ioGgBw; s_tempdata-1014563062=ved=CFoQvxs&ei=cxDEUf3OAsiekQXjiYCACA; d9ji4.resume=uFMMXRoSxnA:183; s_tempdata-1950472349=ei=ywzMUcPiJqekmQXrtIC4Cw&ved=CCMQvxs; s_tempdata-350957551=ei=UxDMUaWGJOTnmAWnmIHICg&ved=CDMQvxs; s_tempdata-3561588006=ei=MD_MUZyPGeTnmAX3koHgBw&ved=CDIQvxs; s_tempdata-1460032003=ei=1VDOUbSyIYjOmgXtyYGAAQ&ved=CA0Qvxs; s_tempdata-2286494229=ei=lFXOUfiMLerbmAXrgoG4Aw&ved=CIABEL8b; s_tempdata-1936772083=ei=lFXOUfiMLerbmAXrgoG4Aw&ved=CH0Qvxs; s_tempdata-190970993=feature=g-high-crv&ei=S9zOUZzYLsi3ygHS9YD4BA&ved=CIgBEPklKAE; __utma=27069237.288981257.1372343761.1372343761.1372511855.2; __utmb=27069237.5.10.1372511855; __utmz=27069237.1372343761.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none); __utmc=27069237; YSC=TwN0bcR_vzM; recently_watched_video_id_list=cc05ffe7b8a53d9d2dbcb9695b1b5354WwEAAABzCwAAAEhTZUltcWJWMzBz; ACTIVITY=1372523413722; PREF=f1=50000000&fv=11.2.202&al=en;" -o ~/Downloads/File.part -r 0-2000000 "http://r4---sn-nau-jhcl.c.youtube.com/videoplayback?id=1d27889aa6d5df4b&ipbits=8&factor=1.25&ms=au&mt=1372523374&fexp=925614%2C906370%2C912519%2C904825%2C900222%2C909546%2C906397%2C928201%2C929123%2C929915%2C929906%2C929907%2C929125%2C929127%2C925714%2C929917%2C929919%2C931202%2C912512%2C912515%2C912521%2C906838%2C906840%2C931913%2C904830%2C919373%2C933701%2C904122%2C900816%2C909421%2C912711%2C907228&mv=m&burst=40&algorithm=throttle-factor&expire=1372545822&sver=3&source=youtube&newshard=yes&cp=U0hWR1VPU19HTENONl9NSVdJOkNGQUpTdVJvVnY0&upn=a9WEy2DAZiY&ip=103.21.166.17&key=yt1&itag=34&sparams=algorithm%2Cburst%2Ccp%2Cfactor%2Cid%2Cip%2Cipbits%2Citag%2Csource%2Cupn%2Cexpire&signature=399599C4C262CCEAED9AB8AEA48A71DDFADFB7CF.08C556136636AFD52BE0318D3E4AECAC1ABFB7C5"

Answer 1

YouTube 服务器似乎不支持范围参数或忽略它。来自cURL docs :

4.11 Why does my HTTP range requests return the full document?

Because the range may not be supported by the server, or the server may choose to ignore it and return the full document anyway.