SRT + NDI Performance Issues

Tracy Peterson 2021-12-21 18:58:14 UTC in Nimble Streamer

I've tried to figure out why NDI is dropping frames at source when transcoding incoming SRT feeds, which shouldn't be happening on a dedicated win10/i7/rtx4000/32GB RAM machine. I tried different network cards, different network configuration, etc. Added cache memory. Nothing seems to work and I can't find any further performance fixes. Other NDI sources work great on that computer to the same RX machines. How can I verify my performance and nimble setup? SRT restreaming has a 99% packet loss to computers on the same switch (more than one switch tried).

Alexander Kalinin 2021-12-21 19:21:52 UTC 

Could you please clarify the stream flow?
e.g. [NDI source > Nimble transcoder > SRT streaming] ?

Regarding the SRT losses, were such essential parameters as 'maxbw' and 'latency' defined in the SRT streaming settings? More details:
To get the SRT stats in realtime for diagnostic purposes, you can use the following Nimble API method:

TRACY PETERSON 2021-12-21 20:53:38 UTC 

SRT source > WAN IN > Nimble > SRT out + Transcoder > NDI

I did set maxbw and latency as listed in that guide, could you verify parameters for a 8000 Kbps stream for maxbw is 8000 and i set latency at various settings from 400ms up

Thank you for the link that is useful all around.

Alexander Kalinin 2021-12-22 07:23:58 UTC 

The 'maxbw' value is defined in bytes-per-second, your defined 'maxbw' of '8000'=8KBps=64Kbps.
Try setting 'maxbw' to '2000000' =2MBps=16Mbps, i.e. twice the actual stream bandwidth for a test.
Also, the 'maxbw' can be set to '0' to trigger its autoselection.

The 'latency' value of '400' =400ms should be okay if you're streaming in LAN.

TRACY PETERSON 2021-12-22 23:09:45 UTC 

Ok maxbw is set and srt is showing very clean on the test player but when it converts to NDI it gets chunky and loses frames. HVEC option in Larix doesn’t show image only audio in either

TRACY PETERSON 2021-12-22 23:44:35 UTC 

Did one more test, rebooted machines, refreshed some things, SRT is working pretty well. maxbw is set to 2000000 and I'm pleased with the results, but NDI is still dropping frames at the encoder. I can't get a solid 60fps out of 1080 60 srt input.

Sergei 2021-12-23 00:13:14 UTC 

Hello, Tracy.

I would suggest opening a new ticket at as we need some sensitive information about your setup. Please include the server name.

Thank you.

MediaUser 2022-03-08 10:52:04 UTC 

Have you reached a conclusion? we have the same packet loss problem in NDI with SRT and NDI together. Our difference is that we pass the NDI directly without going through a transcoder-nimble, the SRTs do. Let's see if you can help us, thanks.

Sergei 2022-03-09 05:53:55 UTC 

Could you open a new ticket at and provide more technical details on your issue.

Thank you.

Yorick 2022-03-28 07:58:16 UTC 

Hello, I have the same drop problem in transcoding from SRT to NDI, so so I'm interested in the solution please.
Thank you

Sergei 2022-03-28 08:45:39 UTC 

Hello, Yorick

This question needs more technical details we can't discuss at the open forum, please open a ticket as suggested above.

Thank you.

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