Issue with jerky/stuttering video in Unreal Flash Player

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Issue with jerky/stuttering video in Unreal Flash Player

Postby Locutus » Thu May 16, 2013 9:54 am

Hello!

I'm experiencing issues with non-smooth/jerky/stuttering playback in Unreal Flash Player.

I installed the free version of UMS on a Windows VM of mine and created a live broadcast of type RTMP Rebroadcast. I'm streaming to that using XSplit on my home PC. Streaming and watching with the Unreal Streaming Media Player (UMS protocol) and KM Player (RTMP protocol) works all okay; stream is butter smooth.

But on Unreal Flash Player which I installed on a web page of mine, the video is very jerky, as if every other to every third frame gets dropped/repeated.

If you need further information about my setup, please let me know! Otherwise I'd be very grateful for hints, because I spent like 10 hours now trying to find out why XSplit/UMS/Flash cannot stream smoothly, while sites like Twitch.tv can... Are they using a better flash player, or a better server?

Thanks a lot in advance!
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Re: Issue with jerky/stuttering video in Unreal Flash Player

Postby admin » Thu May 16, 2013 10:46 am

Try to set a bigger buffer length in Unreal Flash Player.
You may also try to use another Flash player such as JW player.
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Re: Issue with jerky/stuttering video in Unreal Flash Player

Postby Locutus » Thu May 16, 2013 1:11 pm

Thanks for your reply!

Buffer time is already set to 5 seconds, still Flash is noticeably jerkier than UMP or KMPlayer... It's most visible in scrolling texts, or slow motions in front of the webcam.

Using a different flash player didn't change much, I tried JW Player and Flowplayer. Both look mostly the same. Is there any advice in terms of codec or flash settings? I mean, Twitch must be doing something different compared to the players I tried, since it's much smoother there.
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Re: Issue with jerky/stuttering video in Unreal Flash Player

Postby Locutus » Thu May 16, 2013 1:13 pm

It's not always that it drops frames, sometimes the scrolling text speeds up and slows down too, as if the local graphics wasn't rendering the video at a constant speed. This occurs in USMP too, just much less noticeable.
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Re: Issue with jerky/stuttering video in Unreal Flash Player

Postby Locutus » Thu May 16, 2013 1:22 pm

Another observation:

The more stuff I have active in the XSplit scene (webcam, videos, screen region), the jerkier the flash video becomes. Right now I have webcam, three videos and a screen region active, and the scrolltext is nearly down to 3 fps. Whereas the USMP video stays almost the same smoothness.
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Re: Issue with jerky/stuttering video in Unreal Flash Player

Postby Locutus » Fri May 17, 2013 6:09 am

More information. It seems that Unreal Media Server does *something* to the stream to give flashplayer a hard time decoding it, is that possible?

I did a test with the following constellation:

XSplit to capture screen, play media file, show webcam
Flash Media Live Encoder to encode (because XSplit doesn't work with MistServer)
MistServer instead of Unreal Media Server
Flowplayer as flash player
Chrome as browser

And playback is as smooth as I'd expect, even when watching it on the same PC.

Any idea why playback works here, and is very very jerky when using UMS? Does it do any transcoding/modification of the stream?
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Re: Issue with jerky/stuttering video in Unreal Flash Player

Postby Locutus » Fri May 17, 2013 9:51 am

I think I found the culprit.

FMLE uses the H.264 "Baseline" profile by default. XSplit uses "Main" or even something higher. When I force XSplit to use Baseline, I get a much smoother flash playback. Looks very good so far.
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Re: Issue with jerky/stuttering video in Unreal Flash Player

Postby admin » Fri May 17, 2013 2:45 pm

Adobe Flash player is known to have pretty bad h.264 decoder. The quaity of decoding is lower than, for example, Windows 7 built-in h.264 decoder that is used when playing in USMP.
Flash player tries not to monopolize the CPU for decoding. You probably have a large resolution frame with a lot of happenings. Notice the CPU usage on the player computer. Also, this may depend on Graphics card of player computer. Flash player may fail to use hardware acceleration, hence CPU is too busy, hence Flash player shits.
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Re: Issue with jerky/stuttering video in Unreal Flash Player

Postby Locutus » Sat May 18, 2013 7:29 am

Thanks again for your feedback, admin! I'll look into the hardware acceleration thing. I know that I checked that it is turned on in the Flash options, but you never know.
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