Suppose a server is hosting a video file. Why is it that sometimes, it requires a full download before playing. Sometimes, I can stream it?

Question

Someone told me that some servers configure it that allow streaming of a file.

OR

Is it a file-encoding problem, not a server configuration problem?

Given a link of the video file, how do I check if that person allows streaming (or play only once downloaded) ? Headers?

Answer 1

As long as the encoding format is such that the information in the file is chronological with respect to the video frames, there is no theoretical possible way for a server to allow downloading but not playing. Think about it. If you have the data, and it's playable after downloading, that portion is playable before downloading is complete.

Answer 2

In order for a file to be streamable, all of the information necessary to initialize the decode and playback engines must be at the beginning of the file. Not all file formats are designed in that way. (for instance, with AVI files usually the index is at the end).

But the server must also be configured to stream. Transferring a file over HTTP or FTP is a different protocol than streaming the file.

So it's both, for streaming to work everything has to be setup correctly, the server and the file must support it. If either one is not set up correctly, then transferring the file usually works. Transferring the file is the conservative or fallback solution.