LearningAPI » Uncategorized

Dynamic Streaming Follow-Up (& Improvements)

Larry B — Thu, 08 Apr 2010 13:13:28 +0000

My Dynamic Streaming article on streamingmedia.com generated some follow-up over at Longtail Video, home of the JW FLV Player. In an email exchange, JW himself, Jeroen Wijering, explained how the JW was handling stream switching, and that in response to my test results, they'd made some changes for the next release (5.2). You will find excerpts of the ensuing email discussion in the comment section of the article page, appearing shortly. In that discussion, Jereon offers a terrific explanation of how it works, and confirms two of the rules of thumb I deduced in my testing:

Encode with a fixed keyframe interval, ideally every 2 seconds or so
Use a bufferlength about 2x the keyframe interval

To quote Jeroen:

Herein lies the tradeoff to be made for dynamic streaming. Higher bufferlengths decrease the likelihood of playback stuttering, but slow down any responses to screensize / bandwidth increases. Hence the rules of thumb for short keyframe intervals and "2x keyframe" bufferlengths.

I've updated the Dynamic Streaming example page to load a build of the player that contains the fix. My testing shows that it performs beautifully - on par with the 1080p player at switching both up and down, with seamless playback during the switch. This will be part of the next release of JW Player, 5.2, now scheduled for around the end of May.

I haven't had any communication from anyone involved with Flowplayer. Their dynamic streaming implementation as tested for this article (bandwidth-check plugin 3.1.3) remains not really useful for during-playback streaming, although it was fine a selecting the correct stream at startup.

Bookmark to:

Dynamic Streaming & Stream Switching with Flash Video

Larry B — Fri, 26 Mar 2010 14:17:44 +0000

My latest article, How to do Dynamic Streaming with Flash Media Server, has been published at streamingmedia.com. There’s a page with code examples and demos of dynamic streaming on this site, as well.

I’d expected that writing this article was going to be an easy, quick process of explaining how to encode multiple files and set up a playlist in a couple of popular Flash video players (JW FLV Player 5.1 and Flowplayer 3.1.5). My problems started when I decided to actually test out the process as documented by Adobe and the player vendors by creating actual bandwidth fluctuations and watching the behavior of the player.

Imagine my surprise when things didn’t always work very well. I started to wonder if the dynamic streaming technology wasn’t really ready for prime-time. Some research led to finding and testing the 1080p player (from flashstreamworks.com), which had simply outstanding switching performance – on the same videos from the same server. So the technology definitely works. [whew!]

After much research, talking to the vendors, and more testing, I came up with some guidelines that make things work pretty well in all the players. Still, there remains some room for improvement in the implementations of dynamic streaming in the popular players I tested, particularly when it comes to detecting bandwidth changes and then smoothly switching streams during playback.

Bookmark to:

Flash Video Performance on the Mac – Finally Some Real Data

Larry B — Mon, 01 Mar 2010 14:15:59 +0000

Is Flash video on a Mac a CPU hog? More than on Windows? If so, why?

Thankfully, someone’s finally done a test to put some data behind the anecdotes. (Doh! Why I didn’t think of doing that?!?) Jan Ozer over at the Streaming Learning Center hastested Flash video vs. HTML5 video, covering all the browsers on both Windows and (Intel) Mac, and Flash versions 10.0 and (the new, performance-optimized) 10.1.

It’s hard to summarize the findings without leaving out important detail, so I recommend looking at Jan’s data directly. The tables are revealing. But in a nutshell, Jan found that where the video decoder can access hardware acceleration, performance is excellent, and where it can’t…not so much. This means that on Windows, Flash is actually slightly more CPU-efficient than HTML5. On the Mac, where Apple has not made API hooks to its graphics hardware acceleration available to software developers, Flash and HTML5 are both hogs – unless you’re using HTML5 in Safari. It suggests that Apple is using graphics acceleration APIs that it’s keeping from others who are developing applications for the Mac. (Kinda smells like what Microsoft was accused of years ago – keeping various Windows APIs secret so that its non-OS products would always have an advantage over competitors. Microsoft has denied this. )

Is it fair – or smart – to withhold powerful APIs from the devleopers who create the applications that make your computer useful and relevant to users? At best. it’s disingenuous for Apple to criticize Adobe for Flash performance on the Mac while keeping access to hardware acceleration under wraps.

In any case, Jan’s tests show that Adobe is continuing to work on this (to the extent that it can). Video performance in Flash 10.1 is improved over 10.0 on both Mac and Windows. On Windows, the difference is dramatic.

Bookmark to: