Homebrew SysDVR-UVC - USB Video Class Sysmodule

[Insektaure]

SysDVR-UVC - USB Video Class Sysmodule​

This sysmodule presents the Nintendo Switch as a standard USB Video Class (UVC) webcam, allowing video capture on a PC without any client software.

Verified working end to end on Linux (ffplay, v4l2-ctl, OBS) and Windows (ffplay, OBS with caveats - see Latency below).

Tested on FW 22.1.0. Latest Atmosphere / Hekate.
Windows 10 1909 / Ubuntu 24.04 LTS.

Features​

• Driverless operation: enumerates as a standard USB webcam (Linux uvcvideo, Windows usbvideo.sys)
• H.264 passthrough: streams the native H.264 video from the Switch's game recording service (grc:d) - no on-console transcoding
• 720p @ 30fps: native output of Nintendo's encoder
• Low latency: tuned for live capture (low-delay SPS, minimal UVC payload headers, render-on-arrival)

Requirements​

• Nintendo Switch with Atmosphere, HOS 5.0 or newer
• A game that supports video capture (recording icon visible)
• A data-capable USB-C cable
• The original SysDVR sysmodule must NOT be installed/enabled: grc:d only supports one client, and both sysmodules also compete for usb:ds. Running both crashes the console at boot.

Install​

• Unzip at the root of your SD card
• Activate the sysmodule with an overlay (e.g. ovlSysmodules) or any other sysmodule manager
• No need to reboot as sysmodule can be enable / disable on-the-fly
• Connect to PC, open the camera "SysDVR-UVC Capture" with a capture software (FFplay from FFMPEG, OBS, ...)

Usage​

1. Connect the Switch to the PC via USB-C
2. Launch a game that supports video capture
3. The PC sees a webcam named "SysDVR-UVC Capture" (VID 046d, PID 0825)

Note: when an application opens the stream, expect up to ~2 seconds of black/garbage before the first picture - that is the Switch encoder's keyframe interval and cannot be shortened.

Linux​

One-time setup: your user must be able to read video devices:

sudo usermod -aG video $USER # then log out and back in

# Or, to grant access immediately without logging out (resets on unplug/reboot):
sudo chmod a+rw /dev/video2

The device creates two nodes: capture + UVC metadata. The numbers are not fixed - the kernel assigns /dev/videoN in detection order, so on a machine with no other camera the Switch gets video0/video1, while a laptop with a built-in webcam typically yields video2/video3.

Find yours with:

v4l2-ctl --list-devices

Look for "SysDVR-UVC Capture" and use its first node (the capture node), or let apps pick "default".

The examples below assume /dev/video2 - substitute your own node.

# Low-latency viewer (this is the reference pipeline)
ffplay -fflags nobuffer -flags low_delay -probesize 32 -analyzeduration 0 \
-framedrop -f v4l2 -input_format h264 -i /dev/video2

# Record raw H.264
v4l2-ctl -d /dev/video2 --stream-mmap --stream-count=300 --stream-to=out.h264

OBS on Linux: add a "Video Capture Device (V4L2)" source, Device"default", Video Format "H.264", 1280x720 @ 30.
Works with low latency.

Windows​

ffplay -fflags nobuffer -flags low_delay -probesize 32 -analyzeduration 0 ^
-framedrop -rtbufsize 32M -f dshow -i video="SysDVR-UVC Capture"

Note: Windows Media Foundation apps (the Camera app, browsers, Teams) do not support H.264 UVC cameras at all - this is a Windows limitation.
DirectShow apps (ffplay, VLC, OBS) work.

Latency​

The stream itself is low-latency by construction (~140 ms to first decoded frame, real-time 33 ms pacing after - measured).

What you experience depends on the player:

• ffplay: fast only with the flags shown above. Plain ffplay buffers its stream-probing backlog and stays a constant 1-2 s behind on any live source - that is ffplay behavior, not the device.
• OBS Linux: fast (V4L2 plugin).
• OBS Windows: a constant ~1-2 s delay caused by OBS itself: its DirectShow H.264 decoder is opened with auto frame-threading and no low-delay flag, which structurally delays output by up to 15 frames. Tracked upstream (obsproject/obs-studio#13462). Until fixed, the reliable workaround is running the tuned ffplay window and adding it to OBS via Window Capture. Always set the source's "Buffering" to "Disable" - "Auto" silently force-buffers H.264 devices.

Audio​

There is none, and there cannot be: standard USB audio (UAC) requires an isochronous endpoint, and the Switch's usb:ds service cannot build a configuration containing one.

Workaround: Bluetooth audio (A2DP sink)​

The Switch can output audio over Bluetooth (HOS 13.0+), and the PC can act as the receiver (an A2DP sink, i.e. pretend to be headphones).
This works on Linux and on Windows 10 since version 2004.

Caveats: Bluetooth adds its own latency (typically 100-200 ms with SBC), so audio will trail the low-latency video slightly.
While Bluetooth audio is active the Switch limits you to two wireless controllers and disables local wireless play - that is a console-side restriction.

Technical Details​

• UVC 1.5, VideoControl + VideoStreaming interfaces, H.264 frame-based format over a bulk endpoint in alternate setting 0
• Codec: H.264 High profile, level 3.2, 1280x720 @ 30 fps, pic_order_cnt_type=2 (no frame reordering possible)
• The stream from grc:d carries no parameter sets; the sysmodule injects SPS/PPS before keyframes. The injected SPS extends Nintendo's original with VUI timing info and max_num_reorder_frames=0 so decoders open in low-delay mode
• UVC payload headers are the minimal 2 bytes (no PTS/SCR): hosts render frames on arrival instead of scheduling against an uncorrelatable device clock

Limitations​

1. H.264-only: apps that cannot consume H.264 webcams will not show video (notably all Windows Media Foundation apps). MJPEG cannot be offered: grc:d outputs pre-encoded H.264, there are no raw frames.
2. Game support: only games with video capture enabled produce frames. On static screens grc:d skips frames entirely - the picture appears frozen until on-screen content changes. Both are console-side behavior.
3. No audio (see above).
4. No dock mode while streaming (USB-C is used for data).
5. Exclusive: incompatible with the original SysDVR sysmodule and any other grc:d client.

Troubleshooting​

• Device not in lsusb at all: check the cable is data-capable, the sysmodule is installed, and no other grc:d / usb:ds sysmodule is present. Check /atmosphere/crash_reports/ and /atmosphere/fatal_errors/ on the SD card for fresh files.
• Enumerates but no /dev/video (Linux): permissions (are you in the video group?) or a descriptor regression - sudo dmesg will show uvcvideo parse errors.
• Black picture in OBS: wrong node selected (the UVC metadata node) - use Device "default", Video Format H.264.
• Stream opens but freezes/lags: read the Latency section

Credits​

• Based on SysDVR by exelix11
• EP0 handling modeled on Atmosphere's ams::usb::DsInterface
• libnx by the switchbrew team

Github : https://github.com/Insektaure/SysDVR-UVC-Capture