Chrome不会为寻找视频文件发出额外的请求

Question

我将尝试实现伪流媒体，我的html如下所示：

<video src="GetVideo.ashx?id=mp4" controls></video>

加载页面后，Chrome 28.0.1500.72 m会发送请求（即使在点击播放之前）：

GET /GetVideo.ashx?id=mp4 HTTP/1.1
Host: localhost
Connection: keep-alive
Accept-Encoding: identity;q=1, *;q=0
User-Agent: Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/28.0.1500.72 Safari/537.36
Accept: */*
Referer: http://localhost/JWPlayerTestMp4Proper.aspx
Accept-Language: ru-RU,ru;q=0.8,en-US;q=0.6,en;q=0.4
Cookie: jwplayer.volume=12
Range: bytes=0-

服务器响应如下：

HTTP/1.1 206 Partial Content
Cache-Control: private
Content-Length: 5186931
Content-Type: video/mp4
Content-Range: bytes 0-5186930/5186931
Accept-Ranges: bytes
Server: Microsoft-IIS/8.0
X-AspNet-Version: 4.0.30319
X-Powered-By: ASP.NET
Date: Mon, 22 Jul 2013 08:13:28 GMT

点击播放后文件开始播放，但问题是如果我尝试寻找未下载的部分，它不会发送该部分的请求，而是等待文件下载到指定位置。在Firefox 22.0中表现相同：第一个请求（页面加载后）：

GET http://localhost/GetVideo.ashx?id=mp4 HTTP/1.1
Host: localhost
User-Agent: Mozilla/5.0 (Windows NT 6.2; WOW64; rv:22.0) Gecko/20100101 Firefox/22.0
Accept: video/webm,video/ogg,video/*;q=0.9,application/ogg;q=0.7,audio/*;q=0.6,*/*;q=0.5
Accept-Language: ru-RU,ru;q=0.8,en-US;q=0.5,en;q=0.3
Range: bytes=0-
Referer: http://localhost/JWPlayerTestMp4Proper.aspx
Connection: keep-alive

首先响应（与Chrome相同）：

HTTP/1.1 206 Partial Content
Cache-Control: private
Content-Length: 5186931
Content-Type: video/mp4
Content-Range: bytes 0-5186930/5186931
Accept-Ranges: bytes
Server: Microsoft-IIS/8.0
X-AspNet-Version: 4.0.30319
X-Powered-By: ASP.NET
Date: Mon, 22 Jul 2013 08:28:19 GMT

第二个请求（在尝试但未下载部分后）：

GET http://localhost/GetVideo.ashx?id=mp4 HTTP/1.1
Host: localhost
User-Agent: Mozilla/5.0 (Windows NT 6.2; WOW64; rv:22.0) Gecko/20100101 Firefox/22.0
Accept: video/webm,video/ogg,video/*;q=0.9,application/ogg;q=0.7,audio/*;q=0.6,*/*;q=0.5
Accept-Language: ru-RU,ru;q=0.8,en-US;q=0.5,en;q=0.3
Range: bytes=2490368-
Referer: http://localhost/JWPlayerTestMp4Proper.aspx
Connection: keep-alive

第二个响应：

HTTP/1.1 206 Partial Content
Cache-Control: private
Content-Length: 2696563
Content-Type: video/mp4
Content-Range: bytes 2490368-5186930/5186931
Accept-Ranges: bytes
Server: Microsoft-IIS/8.0
X-AspNet-Version: 4.0.30319
X-Powered-By: ASP.NET
Date: Mon, 22 Jul 2013 08:35:34 GMT

IE 10的工作方式与Firefox相同。

Chrome希望响应头能够做出相同的行为——在跳转到未下载部分后进行其他请求。

- MnZrK

Answer 1

结果表明响应头是正确的。 问题在于我使用了长度较短的视频文件，Chrome似乎有某种优化，如果时间差太小（小于30秒左右），就不会发送额外的请求。

- MnZrK