Slow framerate on some software that reads OBS Virtual Camera

[janmonterrubio]

I'm using a copy of the web_cam filter program to just use the camera as a passthrough for some testing (will add open cv on top of it).

Here's the modified version:

# This script is the sample from the README.

import cv2

import pyvirtualcam

cap = cv2.VideoCapture(1)

pref_width = 1280
pref_height = 720
pref_fps_in = 30
cap.set(cv2.CAP_PROP_FRAME_WIDTH, pref_width)
cap.set(cv2.CAP_PROP_FRAME_HEIGHT, pref_height)
cap.set(cv2.CAP_PROP_FPS, pref_fps_in)

# native format UYVY
with pyvirtualcam.Camera(width=pref_width, height=pref_height, fps=15, fmt=pyvirtualcam.PixelFormat.BGR, print_fps=True) as cam:
    print(f'Using virtual camera: {cam.device}')
    print(f'Using {cam.native_fmt}')
     # RGB
    while True:
        ret, frame = cap.read()

        og_frame = frame

        cam.send(og_frame)
        cam.sleep_until_next_frame()
        cv2.imshow('preview', og_frame)
        cv2.waitKey(1)

I noticed there's slow (really slow about 5ps) frame rate on MS Teams when it reads from the pyvirtualcamera:

Compared to just using obs directly:

For sanity, I also compared zoom with pyvirtualcamera and obs and the frame rate didn't seem to differ:

I'm not entirely sure what other things I can do to diagnose this.

I compared a bit what exists in: https://github.com/letmaik/pyvirtualcam/tree/main/pyvirtualcam/native_macos_obs vs https://github.com/obsproject/obs-studio/tree/master/plugins/mac-virtualcam

And there seems to be a couple of changes around a memory leak and some IOSource stuff.

I'm on an M1 Mac.

To further muddle this, a test on a non M1 mac doesn't seem to suffer from the same problem, so I'm guessing it may be related to something with newer macs.

I appreciate any insight you have and any time you take to read this through.

Specs

• Mac OS Monterrey 12.5
• Apple M1 Pro
• Memory 16GB
• OBS 27.2.4
• Pyvirtualcam 0.9.1 (built from source)

[letmaik]

On the non M1 Mac, did that run the same macOS version and OBS version?

[janmonterrubio]

Here's the samples for a simple electron App. I think this is probably something with the video format and electron? that's the one consistent difference I can notice.

[letmaik]

Very odd, thanks for replicating this.
The native format of the mac OBS virtual cam is UYVY. pyvirtualcam converts the input frames that it gets from Python (in your script BGR) automatically into UYVY and that happens in C++ and is fast. It happens in all cases, both Zoom and Teams etc., so that can't be the issue.
Do you see the same issue in Safari? For example, using the online version of Teams or some webcam test page.

[janmonterrubio]

Unfortunately, safari does not recognize OBS virtual cam.

However I did download firefox and tried it.

so this may be a chromium bug :(

[IDDD-Dennis]

Facing similar issue where virtual camera works with Zoom on Mac M1 but not Teams or Slack. Were you able to find a solution?

[janmonterrubio]

Negative, but I also have not tried the latest version of OBS. Are you using the updated 28.x OBS and pyvirtualcam 0.10ish (you probably have to build from source), that's what I had to do.

[janmonterrubio]

This can be closed, see #100