点播视频流
我目前正在研究直播和点播流媒体的不同流媒体方法。
我已经阅读了有关多播和单播的内容，现在我遇到了以下问题，但我找不到答案。
“是否可以通过多播进行点播流媒体？”
我的理解是，当使用多播时，媒体服务器会创建一个视频流，该视频流仅播放一次，用户可以连接并观看。
是因为多播只允许直播吗？如果没有，有人可以向我解释一下它是如何工作的吗？
I'm currently researching different streaming methods both for live and on-demand streaming.
I've read about both multicast and unicast, and now I got the following question, which I can not find an answer to.
"Is it possible to make on-demand streaming with multicast?"
The way I understand it is, that when using multicast, the media server creates a stream of the video, which only is played once, which users can connect to and watch.
It it because multicast only allows live streaming? If not can someone please explain to me how it works?
如果你对这篇内容有疑问，欢迎到本站社区发帖提问 参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。
绑定邮箱获取回复消息
由于您还没有绑定你的真实邮箱，如果其他用户或者作者回复了您的评论，将不能在第一时间通知您！
发布评论
评论（3）
从技术上来说，是的。实际上，不。
你理解正确。就是这样。
Technically, yes. Practically, no.
You understand it correctly. And that is that.
好吧，你可以做到，但更大的问题是你为什么想要它？
点播建议您在单个观众想要观看特定内容时开始广播。如果单个用户选择内容及其开始时间，为什么要多播它？
Well, you can do it, but the bigger question is why would you want it?
On-demand suggests that you start the broadcast at the time that a single viewer wants to see that particular piece of content. If a single user chooses the content and the time it is started, why would you want to multicast it?
是的，可以做到，但有一些注意事项。如果您乘坐旧飞机飞行，您可能会看到旧的娱乐系统，提供 20 个频道，每个频道上有一部电影。频道都在滚动，一旦节目结束，它们就会重新启动。这比在投影仪上只播放一个频道要好，因为它可以让用户选择观看什么内容，但不能自由选择何时观看。
现代飞行娱乐系统都是点播式的，每个乘客都可以随时观看任何电影。那么多播如何帮助解决这个问题呢？如果您检测到多个用户正在观看同一部电影，并且需要注意的是同时，您可以仅使用一个多播频道替换每个用户的流。这在技术上是精明的，但你必须问为什么要这样做？仅当通信介质可感觉或不足以同时为每个用户提供服务时，这才有意义。
设计一个无法适应每位乘客实际使用的飞行娱乐系统是有点短视的。因此，系统可以处理每个用户的流的最坏情况，这意味着多播任何内容都没有任何好处。
一些有线/卫星网络实现多播流并使用时间窗口将尽可能多的观众聚集在一起。例如，观看视频时最多等待 5 分钟，同时显示臭名昭著的短语“缓冲”。
Yes, it can be done, but there are caveats. If you take a flight on an old plane you may see an old entertainment system that offers say 20 channels with a movie on each. The channels are all rolling and once the programmes have finished they restart. This is better than having just one channel broadcast on a projector as it gives the user choice of what to watch but doesn't give them the freedom of when to watch.
Modern flight entertainment systems are all on-demand, every passenger can watch any film at any time. So how can multicast help there is the question? If you detect that multiple users are watching the same film, and the caveat being at the same time, you can replace the streams to each user with just one multicast channel. Which is technically savvy but you have to ask why would you do this? This only makes sense if the communication medium is feeliable or insufficient to serve every user simultaneously.
Designing a flight entertainment system that does not scale to every passenger actually using it is a bit short sighted. Therefore the system can handle the worst case of a stream for each user, meaning there is no benefit for multicasting anything.
Some cable/satellite networks implement multicast streaming and use time windows to group as many viewers together as possible. For example wait up to 5 minutes to watch a video whilst displaying the infamous phrase "buffering".