[koakuma-chan]

> Why would the browser send byte range requests for video tags if it expects to play the file back linearly from beginning to end anyway?

Probably because byte range is required for seeking, and playing from the beginning is equivalent to seeking at 0.

> Wouldn't that be additional overhead/round-trips?

No because the range of the initial byte range request is the whole file (`bytes=0-`).

[EE84M3i]

My original comment was about the commenter I replied to saying:

> To my knowledge, video stream requests chunks by range and is largely client controlled. It isn't a single, long lived http connection.

Wouldn't a byte range request for the whole file fall under the "single, long lived http connection"? Sure it could be terminated early and another request made for seeking, but regardless the video can start before the whole file is downloaded, assuming it's encoded correctly?

[koakuma-chan]

> Wouldn't a byte range request for the whole file fall under the "single, long lived http connection"?

Yes, it would (though a better description would be "a single, long lived http request" because this doesn't have anything to do with connections), and wewewedxfgdf also replied Yes.

> Sure it could be terminated early and another request made for seeking, but regardless the video can start before the whole file is downloaded, assuming it's encoded correctly?

Yes.

[tedunangst]

The client doesn't want to eat the whole file, so it uses a range request for just the beginning of the file, and then the next part as needed.

[koakuma-chan]

The client would actually request the whole file and then terminate the request if the file is no longer needed. This is what browsers do at least.

[lxgr]

Both are possible, and in fact I could imagine not all servers being too happy with having to trickle data over a persistent HTTP connection through the entire length of the video, with an almost always full TCP send buffer at the OS level.

[koakuma-chan]

> Both are possible

It is possible if you are in control of the client, but no browser would stream an mp4 file request by request.

> with an almost always full TCP send buffer at the OS level

This shouldn't be a problem because there is flow control. Also the data would probably be sent to the kernel in small chunks, not the whole file at once.

[lxgr]

> It is possible if you are in control of the client, but no browser would stream an mp4 file request by request.

I believe most browsers do it like that, these days: https://developer.mozilla.org/en-US/docs/Web/Media/Guides/Au...

> This shouldn't be a problem because there is flow control.

It's leveraging flow control, but as I mentioned this might be less efficient (in terms of server memory usage and concurrent open connections, depending on client buffer size and other variables) than downloading larger chunks and closing the HTTP connection in between them.

Many wireless protocols also prefer large, infrequent bursts of transmissions over a constant trickle.

[tsimionescu]

Are you sure browsers would try to download an entire, say, 10h video file instead of just some chunks of it?

[koakuma-chan]

Common sense tells me there should be some kind of limit, but I don't know what it is, whether it's standardized and whether it exists. I just tested and Firefox _buffered_ (according to the time range) the first 27_000~ seconds, but in the dev tools the request appeared as though still loading. Chrome downloaded the first 10.2 MB (according to dev tools) and stopped (but meanwhile the time range was growing from zero approximately by one second every second, even though the browser already stopped downloading). After it played for a bit, Chrome downloaded 2.6 more MB _using the same request_. In both cases the browser requested the whole file, but not necessarily downloaded the whole file.