Top positive review
Works with Linux Ubuntu 16.04LTS and USB2.0!
Reviewed in Canada on April 17, 2020
Linux Ubuntu 16.04.6 LTS desktop computer (kernel 4.4.0-127)
Core i7-860 CPU
Gigabyte GA-P55M-UD4 motherboard (only has USB 2.0)
My camera: Nikon D750 or Olympus EM10mk2 both produce 1080p/60fps HDMI signal.
I was surprised the MiraBox-HSV321 works with my Linux desktop computer from 2011 which only has USB2.0 and no USB3.0 at all. It worked right out of the box and no driver to install.
How is this even possible when USB2=0.48Gb/s while HDMI_1080p30=1.58Gb/s?
Using a program called "usbtop", I was able to determine the transfer rates:
ExternalHD USB3.1 read: 31MBytes/sec (My motherboard's real-world maximum USB2.0 throughput)
Logitech C200 (640x480/30fps) webcam: 31 MBytes/sec (Constant rate, regardless of video content)
MiraBox-HSV321 HDMI (1920x1080/30fps): 2.4-5.8MBytes/sec (Rate are lower when video has less motion)
Obvious it uses compression and through this USB2.0 connection (which I later found out was encoded as MJPEG), I could get 1920x1080p feed coming from my Olympus EM10mk2 or Nikon D750 camera. Using OBS Studio, I measured only 21fps (not 30fps), which was done by recording a video of a stop watch, examining the file and each frame one-by-one (1.0 sec span had only 21unique frames). I also measured a 0.24sec round-trip latency by having the recording include both stopwatch and the OBS Studio preview screen. This lag can cause audio minor sync issue; to fix this, I use my camera's microphone audio, streamed as HDMI audio, and not use audio from a headset directly attached to the computer.
On a ZenBook UX391UA with USB3.0 running Windows10, the MiraBox could get the full 60fps also at 1920x1080. Examining frame-by-frame, there were no duplicate frames and all 60frames within 1.0 sec were unique. In this case, latency was down to 0.20sec. (The same experiment shows my Elgato-HD60S with 0.14sec lag.)
Because MiraBox acts like a webcam (USB V4L2 device on Linux), may other applications can use it such as Skype, Zoom Teleconference, Ring Central Meetings, all on either Windows10 or Linux Ubuntu. (My Elgato-HD60S is only available on Windows and works with Zoom and RingCentral but not Skype.)
While both Raspberry Pi 3b and Pi4b can capture it as 1080p-25fps MJPEG saving to SDcard with less than 1% CPU, re-encoding to H.264 is only usable with the Pi4b hardware encoder. The MiraBox will drain quite a bit of power from your Raspberry Pi. For me, 5.0volt+3.0Amp power supply attached to my Pi was sufficient.
The MiraBox package came with a 55cm/23in USB-A male to USB-A male cable (not common), the MiraBox itself and a manual which recommend installing "PotPlayer" for Windows. However, it does not come with any HDMI cables.