How to send chunks of video for streaming using HTTP protocol?

Question

I am creating an app which uses sockets to send data to other devices. I am using Http protocol to send and receive data. Now the problem is, i have to stream a video and i don't know how to send a video(or stream a video).

If the user directly jump to the middle of video then how should i send data.

Thanks...

Answer 1

HTTP wasn't really designed with streaming in mind. Honestly the best protocol is something UDP-based (SCTP is even better in some ways, but support is sketchy). However, I appreciate you may be constrained to HTTP so I'll answer your question as written.

I should also point out that streaming video is actually quite a deep topic and all I can do here is try to touch on some of the approaches that you might want to investigate. If you have control of the end-to-end solution then you have some choices to make - if you only control one end, then your choices are more or less dictated by what's available at the other end.

If you only want to play from the start of the file then it's fairly straightforward - make a standard HTTP request and just start playing as soon as you've buffered up enough video that you can finish downloading the file before you catch up with your download rate. You don't need any special server support for this and any video format will work.

Seeking is trickier. You could take the approach that sites like YouTube used to take which is to simply not allow the user to seek until the file has downloaded enough to reach that point in the video (or just leave them looking at a spinner until that point is reached). This is not the user experience that most people will expect these days, however.

To do better you need to be in control of the streaming client. I would suggest treating the file in chunks and making byte range requests for one chunk at a time. When the user seeks into the middle of the file, you can work out the byte offset into the file and start making byte range requests from that point.

If the video format contains some sort of index at the start then you can use this to work out file offsets - so, your video client would have to request at least enough to get the index before doing any seeking.

If the format doesn't have any form of index but it's encoded at a constant bit rate (CBR) then you can do an initial HEAD request and look at the Content-Length header to find the size of the file. Then, if the use seeks 40% of the way through the video, for example, you just seek to 40% of the way through the encoded frames. This relies on knowing enough about the file format that you can calculate an appropriate seek point so that you can identify framing information and the like (or at least an encoding format which allows you to resynchonise with both the audio and video streams even if you jump in at an arbitrary point in the file). This approach might also work with variable bit rate (VBR) as long as the format is such that you can recover from an arbitrary seek.

It's not ideal but as I said, HTTP wasn't really designed for streaming.

If you have control of the file format and the server, you could make life easier by making each chunk a separate resource. This is how Apple HTTP live streaming and Microsoft smooth streaming both work. They need tool support to pre-process the video, and I don't know if you have control of the server end. Might be worth looking into, however. These also do more clever tricks such as allowing a client to switch between multiple versions of the stream encoded at different bit rates to cope with differences in bandwidth.