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Wowza hits 100% CPU and crashes with Transcoding of 4K stream to 1080p and 720p

We have WSE running on Linux instances on Google Cloud Platform. These are beefy 8 core machines with 32 Gb RAM. We are attempting to stream 4K @ 30 fps with 12000 Kbps bitrate and have it transcoded to 1080p and 720p renditions. We are finding that with transcoding on the CPU on these boxes goes to 100% in a few minutes.

What are the requirements for 4K streaming + transcoding? Are there any recommended settings or configuration for this?

Hi Sir,

Scrolling down and found your post. Is the 12000 kbps is the actual requirement by the client? Try to lower the bitrate a bit, let say 5000-8000 kbps and see if the CPU still spike or not.

We have found that 12000 Kbps seems needed to get the video quality we desire. (That is the Wowza recommended bitrate for 4k). I will test to see what bitrate works with 4K + transcoding. I know I can stream to this box at 1080p with 2000Kbps.

Transcoding is a resource-intensive process; and particularly with 4K. The bitrate is of lesser important (although still makes a different), the most important factor is the resolution.

  • Your server’s CPU must decode 3840 x 2160 pixels, where each pixel contains 1.44Kbit data.
  • Thereafter, you want to scale the signal to respectively 1920 x 1080 pixels, and 1280 x 720 pixels
  • And finally, you want to encode the scaled picture with a video codec (e.g. H264)

And all that must happen 30 times per second.
So I’m not sure if your CPUs can do that. Try to use a smaller video resolution as input, e.g. 1080p, but still at 12Mbps and see if the CPU usage does down. Experiment with a few resolutions and bitrates until you’ve found the limits of your CPU.

An alternative is to use GPU, e.g. NVidia Tesla (that’s the only real GPU that is supported by Wowza atm)

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Appreciate if you can share the outcome once you try playing with that bitrate ya.


What codec are you using currently? i think this is doable if you use H.265 codec. but ya, it will cost you on hardware. since h.264 is too much to handle 4K

I suggest you read how youtube presents videos - up to 1080p, and -4K etc.
Just don’t be surprised.

We found the issue was our hardware setup. We increased our resources to better processors and 32GB RAM and the issue resolved.

Thanks Dan for marking this as the answer. 4K does consume a lot!