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I am using Azure Blob Storage to store a video. I would like a user to be able to scroll the video to any point in time and play it from there.

For short videos, there is no problem because the whole video loads and you can do that, but for larger videos, it does not seem to work out of the box. And in some sense it makes sense - files by default do not have the functionality to be downloadable from the middle. But all decent video streaming websites offer this functionality. I must be missing some video concepts, would appreciate, if someone linked me to some articles explaining how things like this are done. Bonus points if the solution is using Microsoft Azure.

Large video example (28 secs, 126MB): https://www.w3schools.com/code/tryit.asp?filename=GP328W3SEY77

Small video example (10 secs, 1MB): https://www.w3schools.com/html/tryit.asp?filename=tryhtml5_video

eddyP23
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  • Azure Blob Storage Service is not Video Stream service. It is simply an object store. Have you looked at Azure Media Service? – Gaurav Mantri Mar 30 '21 at 09:29

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Video streaming servers or cloud services are usually dedicated specialised servers and their functionality can be quite complex.

A video 'file' typically consists of one or more video and audio tracks in a 'container' like MP4. The container will have header information and pointers to the track info.

Simple HTTP streaming of an mp4 file is possible if your server supports range requests, i.e. downloading parts of the file at a time, and if the header information is at the start of the video file - in mp4 is it usually at the end by default but can be moved to the start.

More sophisticated streaming servers, including most/all of the popular commercial services, use a dedicated streaming protocol, typically ABR HLS or DASH these days. These provide chunked multiple different bit rate versions of the video and allow the client switch between bit rates for each chunk it downloads - see more info here: https://stackoverflow.com/a/42365034/334402

The thumbnails you see when you scroll along a video timeline are actually usually a separate track in the video file or stream. They are a set of images at timepoints and the entire set of thumbnails can be downloaded quickly at the start of playback to give a view of what a particular part of the video will look like if the user wants to jump to it. When the user actually jumps to that section of the video, the client requests from the server the chunks or section of the file corresponding to that thumbnail.

Mick
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Azure CDN actually provides some nice functionality:

  • video starts to play instantly (browser doesn't need to wait for the video to fully load)
  • you can scroll back/forward in time.

(Obviously, this in addition to the standard CDN functionality of multiple PoP, caching, etc.)

The above CDN setup was tested on Standard Microsoft, but Verizon and Akamai seem to be offering similar functionality.

eddyP23
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