Hi everyone,


I'm a multimedia person at our church, and I'm experiencing frame drops when capturing an extended desktop using NewTek Scan Converter or Sienna NDI Scan Converter on our M1 iMac.

We’re capturing the NDI feed from the iMac on a Windows desktop running vMix for live streaming.


It doesn’t seem to be a network bandwidth issue — we’re using a 2.5Gbps local network with an AV switch — because capturing a mirrored display, ProPresenter output, or even a Chrome window (like YouTube) works flawlessly with no frame drops. However, I specifically need to capture the extended desktop because I can’t quickly switch between sources all the time, and I also need to capture MP4 video files — and that’s where the frame drop happens.


With NewTek Scan Converter, both displays are captured in one screen (limited to 2 displays on M1 iMac, while our Windows laptop can handle more), and the frame rate drops significantly. To fix this, I purchased Sienna’s paid NDI Scan Converter, which captures the extended display individually and performs better — though the colors appear darker and there’s still a small amount of frame drop.


Gemini and ChatGPT suggested the issue might be due to the M1 chip’s CPU/GPU limitations. Interestingly, when I tested the same setup on our older 2021 Windows laptop (i7-10750H, RTX 2060 6GB, 16GB RAM), there were some frame drops when capturing the full desktop, but much less than on the M1 iMac — and there were no drops when capturing specific app windows.


So my questions are:


1. Is this really due to the CPU/GPU limitations of Apple Silicon (especially M1)?


2. Has anyone had success with smooth NDI capture of extended displays using newer M3/M4 Macs or higher-end Windows systems?


Thanks in advance for your insights!