Flash H.264 "Intelligent" Fast-start... compared..

[Deke Ryland]

I've worked with progressive download Quicktime H.264 web videos that play in Quicktime Player and really like how Quicktime intelligently knew when it could start playing the video when it realized that the user has downloaded enough and was downloading the rest fast enough to watch the video in its entirety without any hiccups or stops.

I was wondering if the new Flash H.264 progressive download videos with Flash Player (any flv players embedded in web pages) worked the same exact way? And if they were just as effective at determining that proper "start time" to eliminate any hiccups or stops at later points in the video.

Thanks for your help.

[Josh Chesarek]

I have not seen anything like that yet. But it would be a cool feature. I will have to forward that to the JW Forums and maybe it could be included right now most players just let you set a time to buffer. IE: Download first 20 seconds before playing.

[Jon Fairhurst]

In Flash you program your own player. You can set it to buffer a certain period (say 5 seconds), and if you're crafty, you can calculate the time needed.

Of course, nothing can predict if your connection will get slower or faster in the future, so any predictive algorithm will be wrong sometimes.

[Stephen Duke]

Hi Deke,

Welcome to the world of indeterminate data flows.

One of the main banes of internet web video delivery (as opposed to say, broadcast) is that we never know what lies between us (the client) and the server providing the video, during (and here's the real catch), the play of the video. It can change!

What does this mean? A scenario :

Let's say you host a video that I want to play.

I can test a connection between you and me, and know that this connection is good for a 300kbps. This tell me that it is going to take 60 seconds to download a file the size of 2.2 megaabytes.

The video I want to play is a 60 second video that is 3 megabytes in size. So, it will stutter if I attempt to play the video as I'm downloading it unless I buffer the first potion of the video. In this case, at least 0.8 megabytes. (Note: you may see some compressors offering 'fast start', well they are compressing the first portion to give you more video time for the data downloaded.)

However, as I mentioned, the internet is an indeterminate medium. So, as I'm downloading the video that bandwidth changes, and I no longer have a 300Kbps connection, but a 128 Kbps connection, and my calculations have just gone up the wazzoo and my video will stutter. And, in flash, a video will not resuming playing until its buffer is full.

With the quicktime player, if you are downloading progressive videos from you web site, then they will also stutter as the bandwidth changes.


So, to help we need to incorporate what is known as 'dynamic buffering' and 'dynamic delivery'. These methods should not only deliver the appropriate video size and buffer size based on our calculated connection at the start of downloading, but also monitor the connection and alter the buffering during download. A video will not START to play until its buffer is full again. (Note: in the case of streaming media, also alter the quality of the video during delivery based of connection performance).

So, basic common method for flash is:

Calculate the connection speed, and set the initial buffer size to 120% of the minimum required size

When ever the buffer is full, make the buffer size BIG, 60 seconds or more. (to hold more data should the bandwidth lower during download)

Once the buffer is empty (low bandwidth), change the buffer size back to 120% of the minium required size.

If you are using a CDN to deliver you videos, then ask them what methods they have available for dynamic delivery.


steve

[Mark Scott]

I'm new and just looking into web delivery. Any chance you could share info on the file type and deliver method you are using on your website. I played several of your reels and all but one buffered perfectly.

Thanks Mark