Possible bitrate bursts too high on ATEM Mini Pro ISO?

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KenJohnson

  • Posts: 5
  • Joined: Sun Mar 07, 2021 8:40 pm
  • Real Name: Ken Johnson

Possible bitrate bursts too high on ATEM Mini Pro ISO?

PostSat Aug 06, 2022 1:27 am

We have been streaming with our ATEM Mini Extreme ISO (and our Atem Mini before it) for several years with no issues. We use CASTR and send video to them for restreaming to YouTube and Facebook.

This has worked well until a couple weeks ago when suddenly Facebook started disconnecting our stream several times each event. We have been troubleshooting with CASTR for a couple weeks and reset the CASTR-Facebook connection multiple times, confirmed we were using their preferred version of the ATEM Streaming.xml file (which really looks like the default one included in the latest software), and while Facebook continues to drop - YouTube is 100% stable.

CASTR did note that they thought our bitrate was jumping a bit high and we agree. We stream at 1080p30 as we have for the last few years without issue and use the Streaming High setting.

According to the Streaming.xml config file in the CASTR section (and just about all others) we should not be exceeding 6kbps while using this setting
<profile>
<name>Streaming High</name>
<config resolution="1080p" fps="60">
<bitrate>9000000</bitrate>
<audio-bitrate>128000</audio-bitrate>
<keyframe-interval>2</keyframe-interval>
</config>
<config resolution="1080p" fps="30">
<bitrate>6000000</bitrate>
<audio-bitrate>128000</audio-bitrate>
<keyframe-interval>2</keyframe-interval>
</config>
</profile>


However we routinely see spikes to 6.8 - and occasionally see a sudden spike to 14 or 15 for a few seconds.

Monitoring - these do seem to possibly correspond to the Facebook drops (not surprising).

We did upgrade to 8.8 a few weeks back, but that did not come with a firmware upgrade so we are still on 8.6.1 as we have been for a long while.

Am I missing something obvious that might be causing the ATEM to occasionaly disrespect the limit and sometimes just outright blast past it?

I have been using computers long enough to know they generally only do what you tell them to do so I'm at a loss as to what I might have wrong if anything.

We have confirmed we've restarted the software and even the atem after confirming we've saved a good copy of streamining.xml in the ATEM Software directory.

We've even setup a Restream.io premium account and while i haven't seen a Facebook drop just yet - Restream is similarly complaining about our sending stream occasionally going out of Facebook and YouTube's preferred limits.

I created a custom setting for 5Mbps and that does seem to have an effect as it averages down around 5Mbps when I use it - but it occasionally spikes up to 6 still, and has even done the 14Mbps spike once.

Thanks for helping me see what I'm possibly missing :-)
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Robert Betzner

  • Posts: 434
  • Joined: Fri Sep 28, 2012 7:54 am
  • Location: Cologne, Germany

Re: Possible bitrate bursts too high on ATEM Mini Pro ISO?

PostSat Aug 06, 2022 7:37 am

Hi Ken,

we don't use the ATEM Mini but we used the Webpresenter HD which should be similar regarding the streaming engine.

I've mentioned this before and talked about the issue with a BMD Rep. but they didn't seem to care. All BMD encoders have the problem that they do variable bitrate not constant bitrate. You can easy test this by setting your Atem to 4MBit video bitrate and switching from a camera image to a still image or a powerpoint slide and back to the camera after 30 seconds. With the camera image you will have a avarage bitrate about 4MBit as set in the profile but as soon as you switch to the still image, the bitrate will drop to around 300-500kBit. That is not the problem but when you switch back to a camera the encoder will spike and go up to 9-10MBit to keep up with the sudden changes in the frame. That spike overpowers most of all network connections and of course most CDNs.

That is why we trashed all of our Web Presenters and bought other encoders that won't exceed the setting that we make. IMHO all BMD encoders are not reliable and prone to pass over the bitrate everytime when coming from a low complexity content to a high complexity one. They are IMHO simply not suitable for solid streaming. Buy some other encoders that do their job well.

Cheers

Robert

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