Switch Frame Tap

Stream your Nintendo Switch games to your PC, with sound, at up to 1080p 60 fps, over a USB cable or your network. No capture card needed.

Switch Frame Tap is a sysmodule (a small background program) for Switch consoles running Atmosphère custom firmware. Install it on the SD card, open the viewer on your PC, start a game.

• Up to 1920x1080 at 60 fps, the game's own resolution, encoded by the console's hardware H.264 encoder.
• USB or network: a USB-C cable in handheld mode, Wi-Fi or LAN when docked.
• Game sound included.
• Low latency: about 45 ms (720p) to 60 ms (1080p) from the game to your PC.
• Viewers for Windows, Linux and macOS, with one Settings panel for everything.
• Record to MP4 with one key, and take native-resolution screenshots.
• Webcam mode: the Switch shows up as a USB camera in OBS, Discord, Zoom or any camera app.
• Optional GPU upscaling in the viewer (AMD FSR 1, NVIDIA NIS, RTX Video Super Resolution on Windows).
• A manager app and an overlay on the Switch for settings, so you never have to edit files.

• A Switch running Atmosphère (firmware 21 to 23; tested on 22.5.0 with Atmosphère 1.11.2, users run 23.0.0 with 1.12)
• A PC with Windows 10/11, Linux or macOS 12+
• A USB-C cable, or the Switch and the PC on the same network

1. Download the -switch.zip from the latest release (or get it from the Homebrew App Store), unzip it onto the root of the SD card and reboot.
2. Download the viewer for your PC from the same release:
   • Windows: unzip it and install the USB driver once with Zadig (how), then open SwitchFrameTap.exe.
   • Linux: unpack it and run the install script (how).
   • macOS: unzip it, drag the app to Applications, right-click it and choose Open.
3. Plug the Switch into the PC (handheld) or pick Network in the viewer (press Tab), then start a game.

The full guide, with every option, is in Install.

• USB only works in handheld mode, because the dock uses the USB port. When docked, stream over the network.
• 1080p over USB needs ReverseNX-RT to make the game render its docked picture in handheld; docked over the network it is 1080p by itself.
• It is experimental homebrew, tested on a few consoles and games. Read Limitations before installing it.

If you like the project and want to support it, you can buy me a coffee. Thank you!

The goal of this project is 1080p at 60 fps: the game's native docked resolution, at full frame rate, on any PC.

Where it is today: 1080p60 works. Over a plain USB cable it streams native 1920x1080 at the game's 60 fps whenever the game renders 1080p, and the console's native 1280x720 at 60 fps in ordinary handheld mode. The USB port is only free in handheld, so 1080p over USB uses ReverseNX-RT to make the game render its docked picture in handheld (Run W: 59.5-59.9 fps sent per 20 s window against the game's ~59.2, 0 errors). See the road to 1080p60 for what is left.

It works, and it is playable. Live mode streams whenever the PC viewer (Windows or Linux) is open and a game is running - with its sound - reattaches by itself when you close the viewer, close the game or start another one, and has been played with Mario Kart 8 Deluxe (60 fps), Zelda: Breath of the Wild and Ocarina of Time on Nintendo Switch Online (30 fps), and homebrew apps started from HOME-menu forwarders. 0 frames lost, 0 undecodable, 0 stale or torn frames in the measured runs; about 45 ms (720p) to 60 ms (1080p) from the game presenting a frame to it being on the PC screen (monitor not included).

Since v0.7.0 it also streams over the network - Wi-Fi or the dock's LAN port - so a docked console streams its native 1080p too, with the quality adapting to what the network carries.

It is still experimental: tested on the author's console (and a Switch Lite by a user). Read Limitations before installing it.

Screenshots taken on the console with the screenshot button (L3 + R3), at the game's own resolution: Mario Kart 8 Deluxe at 1920x1080 (docked picture through ReverseNX-RT, in handheld), Ocarina of Time on Nintendo Switch Online at 1280x720 - the same frames the stream sends.

Recorded with the viewer's R key (v0.5.0): Mario Kart 8 Deluxe at native 1920x1080, 60 fps (the docked picture through ReverseNX-RT, in handheld). The animation is 4 seconds of it scaled down; the whole 30-second recording (381 MB, 1080p60 with sound) is the file exactly as the viewer saved it - the console's own H.264, never re-encoded: 1792 frames, 59.3 fps, 0 decode errors.

A frame off the live stream, decoded on the PC from the console's own H.264 (Run M, live mode). A 6.7 s clip of the stream is the console's bitstream exactly as it arrived over USB, only put in an MP4 container: 60 fps, keyframe every 60 frames. Below, the same clip as a small animation.

For comparison, SysDVR, the established tool, is capped at 720p30 for game video, because it reads the system's own game-recording encoder, whose settings are fixed in firmware. This project takes the frame before that encoder.

the game presents a frame (queueBuffer)
  | vi:u mitm (games) / vi:m mitm (homebrew) sees it: which swapchain slot,
  | and the GPU fence for it
  v
take the newest frame the GPU has finished (or wait for the next one)
  v
svcReadDebugProcessMemory: copy the slot out of the game's memory
  |   (the kernel debug SVCs - the only route to another process's pixels)
  v
VIC: RGBA block-linear -> BT.709 NV12 (the Tegra's video compositor)
  v
NVENC: H.264, IDR + P frames (the job the system's own recorder builds)
  v
USB bulk -> the viewer on the PC (Windows / Linux): libusb + libavcodec + SDL2

grc:d (the console's own recorder): the game's sound, 48 kHz stereo PCM
  -> the same USB stream, a packet before each frame -> played in step

The sysmodule never touches the GPU or the display stack's buffers directly. It watches the game's display traffic through a vi:u mitm (and homebrew's through vi:m, for the running application only), reads the finished frame with the same debug SVCs Atmosphère's cheat engine uses, and drives the VIC and NVENC engines itself over raw nvdrv ioctls. The sound comes from grc:d, the recorder behind the console's own video clips.

Required - enough to stream at 720p60, take screenshots and use the manager app:

Optional - one per feature. Since v0.7.5 the manager app's Get extras installs each of them from its author's GitHub release (see below); or download them yourself from the links:

Nothing else: no other sysmodule, no sigpatches, no capture card.

This drives hardware engines directly; a bug can freeze the console (see If something goes wrong).

1. The Switch. Download switch-frame-tap-0.7.12-switch.zip from the release and unzip it onto the root of the SD card (card reader or Hekate USB mass storage). It contains:

atmosphere/contents/0100000000000C20/        the sysmodule (starts at boot)
switch/switch-frame-tap/switch-frame-tap.nro  the manager app (homebrew menu)
switch/.overlays/switch-frame-tap.ovl         the overlay (Tesla / Ultrahand)

Reboot. Updating later is the same: unzip over it; your settings are kept.

2a. The PC viewer on Windows. Unzip switch-frame-tap-0.7.12-windows-viewer.zip anywhere. Once, with the Switch connected and running: open Zadig, Options -> List All Devices, pick Switch Frame Tap (USB ID 1209 5F1E - make sure it is that one), choose WinUSB and Install Driver. Then double-click SwitchFrameTap.exe (keep the two DLLs next to it; the zip is 2 MB). Windows may warn about an unknown publisher: More info -> Run anyway.

2b. The PC viewer on Linux (any distribution - Ubuntu, Fedora, Arch, Bazzite, SteamOS - x86_64). Unpack switch-frame-tap-0.7.12-linux.tar.gz and run ./install.sh: it puts Switch Frame Tap in the applications menu and prints the one sudo command that installs the USB rule (lets the viewer open the Switch). It is a single program with FFmpeg, SDL 2 and libusb built in.

To build it from source instead (Ubuntu/Debian):

sudo apt install build-essential libusb-1.0-0-dev libsdl2-dev libavcodec-dev libavutil-dev libavformat-dev
sudo cp tools/raw-recv/99-switch-frame-tap.rules /etc/udev/rules.d/
sudo udevadm control --reload-rules && sudo udevadm trigger
bash tools/raw-recv/install-launcher.sh

2c. The PC viewer on macOS (v0.7.11; Apple Silicon or Intel). Unzip switch-frame-tap-0.7.12-macos-arm64.zip (Apple Silicon) or -x86_64.zip (Intel) and drag Switch Frame Tap.app to Applications. It is not signed by Apple: the first time, right-click it and choose Open. No USB driver is needed. Thanks to proconsule54 and DiM3NT0R for the first macOS builds.

On all of them, the viewer opens a window that says what it is waiting for (the Switch, its USB driver, or a game) and lists its keys; the same screen comes back whenever the game is closed or not on screen (the HOME menu) instead of a frozen frame. It reconnects on its own and closes only when you close it. It plays the game's sound on the default audio device.

The home screen: what the viewer is waiting for, USB or network	Settings (Esc or the gear): every option, mouse or keys
Picture controls (P)	The full stats overlay (O / F3) and the recording timer (R)

It reads USB, decodes and draws on separate threads and shows the frames in order, one per screen refresh (vsync), so the picture stays smooth. Its statistics - frame rate, latencies, decode and draw times, once a second - go to the terminal on Linux and to %APPDATA%\switch-frame-tap\viewer\viewer.log on Windows.

Hardware decoding (v0.7.12): the viewer decodes with the graphics card's video decoder - about 5 ms less latency in busy scenes and no keyframe stutter - and falls back to the CPU by itself. On by default on Linux (VAAPI for AMD and Intel, the Steam Deck included, or NVDEC for NVIDIA - since v0.7.13 also in the ready-made Linux download, which loads the system's libva only if it is there); on Windows (D3D11VA) and macOS (VideoToolbox) it is still being tested, so it is off by default there - turn it on in Settings and tell us how it goes. --software (or hwdec=0 in viewer.ini) decodes on the CPU.

GPU upscaling (v0.7.11, off by default): when the window or fullscreen is bigger than the stream (say 1080p shown on a 1440p or 4K monitor), U sharpens the enlargement on your graphics card instead of a plain stretch. FSR 1 (AMD FidelityFX Super Resolution) works on any GPU with OpenGL 4.3; NIS (NVIDIA Image Scaling) too, despite the name; on macOS, FSR 1 runs on Metal (since v0.7.13, DiM3NT0R's PR #14); on Windows, RTX VSR uses an RTX card's own AI upscaler (turn on RTX Video Enhancement - Super resolution in the NVIDIA app or Control Panel; it costs a few milliseconds of latency). Recordings and screenshots keep the console's own picture.

The stats overlay (v0.7.2): O or F3 steps through four levels - off; FPS, a counter in the corner (yellow or red when frames come unevenly); graphs, frame rate, bitrate and latency with a frame-time graph and a latency graph split into the Switch's part and the PC's; and full, every number the viewer keeps (decode and draw times, skipped frames, lost packets, keyframes, the audio buffer, ...) with six graphs. It scales with the window, and the level is remembered.

Recording (v0.5.0). Press R in the viewer: from the next keyframe (within a second) it saves an MP4 to Videos/Switch Frame Tap - the console's H.264 exactly as it arrived, never re-encoded, so no quality is lost and it costs almost no CPU, plus the game's sound (AAC). R again stops. A red dot shows while it records, and the title bar the time and size. At 1080p it is about 10 MB a second (~600 MB a minute) at High quality, half that at Medium. The file is written in fragments, so a recording cut short by closing the window or pulling the cable still plays; if the game switches between 720p and 1080p mid-recording it continues in a new file; it will not start with less than 1 GB free and stops by itself below 500 MB.

3. Stream. Connect the Switch (handheld) to the PC with the USB-C cable, open the viewer and start a game. The picture appears a few seconds after the game is on screen (at the earliest 20 s after boot). Close the viewer or the game whenever you like; the stream picks up again when both are back.

1080p. Install SaltyNX and ReverseNX-RT and pick Docked (1080p) in the Switch Frame Tap overlay (or ReverseNX-RT's own): the game renders its docked picture and the stream switches to 1920x1080 by itself. 1080p60 wants CPU 1785 MHz (Nintendo's own boost clock; GPU 768 / RAM 1600, the docked values) from a clock tool such as Horizon OC or sys-clk; at the stock 1020 MHz it runs, a little below 60. Expect more heat and battery drain, and some games dislike fake docked mode (MK8D crashes with Joy-Cons attached; use a Pro Controller).

The manager app from the homebrew menu (status and connection, picture and screenshot settings, the setup check) and the overlay over a game - v0.7.0, captured on the console.

Switch Frame Tap in the homebrew menu: what the stream is doing (and its frame rate), streaming on/off, start with the console, USB mode (PC viewer or webcam), picture quality (High/Medium/Low), keyframe interval, maximum resolution (1080p/720p), game audio on/off, sound in no-record games, start delay, screenshots, Get extras (below) and a setup check. Changes apply at once - a running stream restarts with them. Settings live in sdmc:/config/switch-frame-tap/config.ini.

The optional tools, installed from the manager app with the Switch online: Ultrahand Overlay (the overlay menu, with nx-ovlloader), SaltyNX and ReverseNX-RT (1080p over USB), and an overclock tool for 1080p at 60 fps - sys-clk or Horizon OC, one or the other. Each row says whether it is installed; A twice downloads the latest release from its author's GitHub page (over HTTPS, checked against the console's own certificates) and unpacks it onto the SD card, keeping the tool's existing settings files. Tools that run at boot need a restart. Horizon OC: its authors warn that RAM overclocking can corrupt the NAND or SD card, an update resets its settings, and with Hekate the boot entry needs kip1=atmosphere/kips/hoc.kip (the manager says when it is missing).

Needs an overlay menu (Tesla Menu or Ultrahand, on nx-ovlloader): stream on/off (remembered across reboots), live status, Stream this app (see below), Enable sound in no-record games (below), and Game default / Handheld (720p) / Docked (1080p) through ReverseNX-RT.

The game's sound comes from the console's own video recorder, and some games turn it off (Super Smash Bros. Ultimate, for one): the picture streams, the sound does not. dvr-patches (by exelix11, made for SysDVR, BSD-3) patch the system so the recorder runs for every game, and then the sound comes through. They come with Switch Frame Tap (v0.7.4), off:

1. In the manager app (or the overlay), turn Sound in no-record games on.
2. Restart the console.

It applies to every game while on. If a game crashes with it (a crash report for 0100000000000023), turn it off again and restart. The patches are kept in config/switch-frame-tap/dvr-patches/; turned on, they are copied to atmosphere/exefs_patches/switch-frame-tap-sound/. They are tied to the firmware: a Switch Frame Tap update brings new ones, and the sysmodule refreshes the copy at boot. dvr-patches installed by hand (in atmosphere/exefs_patches/am) are recognised, and the switch turns them off too. (Recording the console's final mix through audrec:u instead was tried: it records, but a game that blocks recording is silent in it.)

Set Connection to one of the two webcams in the manager and restart the console: the Switch then shows up on the PC as a USB camera, Switch Frame Tap Camera. No viewer and no driver. The camera app picks the size; the picture is scaled to it.

The "any app" camera sends every frame uncompressed straight from the console's video engine, so nothing on the PC has to decode it (no decoder delay either); USB 2.0's ~37 MB/s is what limits 720p to 25 fps.

1080p60 in any app: use webcam (OBS), add it in OBS as a Video Capture Device, click Start Virtual Camera, and pick OBS Virtual Camera in Discord, Zoom, Teams, the Camera app or the browser. (An uncompressed 1080p frame is 3.1 MB - about 11 fps over USB 2.0 - so the "any app" camera stops at 720p.)

• OBS: add a Video Capture Device, pick Switch Frame Tap Camera, and set Buffering to Disable. Latency is higher than with the viewer: OBS's H.264 camera decoder holds back several frames (an OBS issue, not the console's). On Linux OBS reads it through v4l2.
• No sound in webcam mode: a USB microphone needs isochronous transfers, which the Switch's USB device service cannot do. Use the viewer for sound.
• The Windows Camera app does not open the H.264 camera (it wants uncompressed or MJPEG cameras): use webcam (any app) for it.
• On Linux, tools/raw-recv/uvc-check (make -C tools/raw-recv uvc-check) streams either camera for a few seconds and reports frame rate and errors (--size 1080|720|432, --shot frame.ppm for the uncompressed one).
• Changing the mode needs a restart (the USB descriptors are set at boot). Set it back to PC viewer the same way.

Measured (Linux, v4l2): H.264 60.0 fps at 1920x1080 and 60.1 fps at 1280x720, 0 decode errors, first frame 0.4-0.8 s after the camera opens; OBS on Windows works. Uncompressed: 26.0 fps at 1280x720 and 60.0 fps at 768x432, every frame complete, first frame 0.4-1.1 s after opening.

The USB camera side follows Insektaure's SysDVR-UVC-Capture (GPL-2.0), whose research into usb:ds control transfers made it possible.

Set Connection to Network in the manager and restart the Switch; in the viewer, press Tab until it says Connection: Network (it is remembered). With the Switch and the PC on the same network - Wi-Fi, a phone hotspot or the dock's LAN port - the viewer finds the console by itself: the address that worked last time, the console's broadcast, or a quick scan of the network (many Wi-Fi routers drop broadcasts between wireless devices, so the scan is what finds it there). I in the viewer types the Switch's IP by hand (the manager shows it). One connection at a time: in Network mode the Switch leaves USB alone.

The stream is the same as over USB - sound, recording, the menu - with one addition: the quality adapts to the network. Five times a second the Switch checks how busy its network sender is; when the link is full it codes the next frames coarser, and when there is room again it steps back to your quality setting. Frames never pile up, so the frame rate and the delay stay steady and the picture gets softer in fast scenes instead.

• Latency is a little above USB (a 1080p frame takes a few ms to cross even a fast network).
• The network decides the picture: a close hotspot or a LAN adapter in the dock is best; a far-away or busy home Wi-Fi drops the quality more often. Max resolution 720p halves what the network has to carry.
• Windows asks once whether to allow the viewer through the firewall on private networks - allow it.

Measured (Run AO, before the rate control): docked 1080p on home Wi-Fi, the Switch's link carried 20-29 Mbps; a fast race at Medium needed ~40, so frames queued - 7-30 fps and 100-350 ms of delay. With the rate control on a phone hotspot: smooth 60 fps, "very playable", latency a little above USB.

Homebrew apps stream too - forwarders on the HOME menu, and the homebrew menu in title-override mode - at the resolution the app draws (usually 1280x720). ReverseNX-RT cannot switch homebrew to docked mode (it works through the official SDK, which homebrew does not use), and most homebrew draws 720p in both modes anyway. Some apps refuse to run while a debugger is attached - the stream reads frames that way - such as TiCo's protected builds: turn Stream this app off in the overlay while one is running and restart it; the sysmodule then never touches it (no stream, no screenshots). The manager's Apps never streamed clears the list.

Turn on Screenshot button in the manager and press L3 + R3 (or another combo you pick there) in any game: the frame is saved as a PNG at the game's own resolution - 1920x1080 docked or with ReverseNX-RT, 1280x720 handheld - in sdmc:/switch/switch-frame-tap/screenshots/, with or without the PC viewer (~0.4 s). With Ultrahand installed a notification confirms it. Browse, view and delete them in the manager (View screenshots). The PNGs are stored uncompressed: exactly the pixels the game drew, ~6 MB at 1080p.

sdmc:/config/switch-frame-tap/log.txt (rewritten at every boot, capped at 4 MB) and last.txt, a one-line breadcrumb that survives a forced power-off. Please attach both to a bug report.

git clone --recursive https://github.com/Atmosphere-NX/Atmosphere ref/Atmosphere
git clone https://github.com/WerWolv/libtesla ref/libtesla
bash tools/make_release.sh 0.7.12      # -> dist/switch-frame-tap-0.7.12-{switch.zip,linux.tar.gz,windows-viewer.zip} (macOS: GitHub Actions)
bash tools/run_pc_tests.sh             # every check that needs no console

Everything builds in the devkitpro/devkita64 Docker image (the first build compiles libstratosphere, ~15 minutes). The PC viewer: make -C tools/raw-recv; the Windows viewer is cross-compiled from Linux with Zig - bash tools/raw-recv/build-windows.sh VERSION (after build-ffmpeg-min.sh once, for FFmpeg built into the exe), toolchain listed in ref/README.md. raw-view --file REC.sft --paced runs a recording through the live pipeline (no console needed).

Test installs. With sdmc:/applet-mitm.armed on the card the sysmodule ignores config.ini and reads its flags from that file instead (vic exec dbg usb nvgop=60 live wait=20 is the release behaviour), logging to sdmc:/applet-mitm.log - how every development run was done.

• USB is handheld only (docked, the dock owns the USB-C port); docked play streams over the network (v0.7.0), where the picture quality depends on the network. One viewer at a time, and one connection (USB or network) per boot.
• 1080p60 wants CPU 1785 MHz. The frame copy runs on the CPU; at the stock 1020 MHz it is slower and 1080p runs a little below 60 (still playable).
• Homebrew: apps that run as applets (the homebrew menu from the album) are not streamed - use a forwarder or title override. Apps with anti-debug protection (TiCo) cannot be streamed; exclude them. Homebrew cannot be forced into docked mode.
• A handful of games tested: Mario Kart 8 Deluxe, Zelda: Breath of the Wild, Ocarina of Time (Nintendo Switch Online), Kirby and the Forgotten Land and several homebrew apps. Others should work if their swapchain is block-linear RGBA or BGRA, at most 1920x1088 and 10.5 MB a buffer; the log says so if not. Games that draw upside down and have the system flip the picture (Kirby: v0.4.1) are flipped back the same way; a 90-degree rotation is not handled (none seen yet - the log would say "rot-90").
• Game audio comes from the console's own video recorder (as with SysDVR): games that turn video capture off have no sound in the stream unless Sound in no-record games is on.
• Webcam mode: picture only; the H.264 camera has higher latency in OBS than the viewer, the uncompressed one tops out at 720p25 (USB 2.0); switching modes needs a restart.
• PC viewer: Windows, Linux (x86_64) and macOS 12+. On Windows the driver needs Zadig once, as with SysDVR.
• Cheats: the stream reads the game directly, like a debugger. When Atmosphère's cheat engine already holds the game (cheats loaded for it), it reads through the cheat engine instead (since v0.7.9, by Laliukz): cheats and streaming work together, but reads are about 5x slower, so a 1080p60 game can drop to 20-25 fps while cheats are loaded. Games without cheats are not affected.
• Occasional micro-stutters during loading and heavy scenes: reads, the VIC and NVENC are shared with the whole system (NVENC also with the console's own background recording), and a frame can take 50-200 ms then.
• Bitrate is set by quality, not capped. v0.6.0 made P frames about 15-20% smaller (QP +2 on P frames, a better motion search); at the same quality x264 needs ~89% of the console's bits, so what remains is the price of "High" (near-lossless) at 1080p60. USB has room for it; a bitrate cap (the console's own rate control) comes with the network transport, where it is needed.
• Game manuals, news and the eShop (the browser applets) need nearly all of the console's applet memory. Since v0.7.10 Switch Frame Tap holds none of it while you are not streaming, and when a game opens its manual or news while you stream, the stream pauses first and comes back when you close it. Since v0.7.11, pressing HOME while streaming ends the stream and gives its memory back (it comes back when the game is on screen again), so they also open from the HOME menu.
• Few consoles tested. The author's Mariko (firmware 22.5.0, Atmosphère 1.11.2), plus users' reports: a Switch Lite on 23.0.0 (Atmosphère 1.12.0), 22.0.0 and 21.0.1.

Turn off Start with the console in the manager and reboot; or delete atmosphere/contents/0100000000000C20/ from the SD card on a PC; or boot holding Volume Up, which makes Atmosphère skip contents sysmodules. Nothing here touches NAND or the bootloader. Keep a NAND backup anyway.

Read the SD card through a card reader or Hekate's USB mass storage, not MTP: MTP returns I/O errors on a log whose tail was cut by a forced power-off. Copy the log off before the console boots Atmosphère again.

I built this together with Claude (Anthropic's AI model, through Claude Code). That should change how you read and trust what's here.

• Claude wrote nearly all of the code and the documentation, did the source-reading (Atmosphère and its kernel mesosphere, NVIDIA's open headers, switchbrew, reference drivers), designed each hardware probe, and interpreted the logs that came back.
• I set the goal and the direction, ran every one of the 87 hardware test cycles on my own console, read the logs back off the SD card, decided which routes to keep pushing and when to drop one, and decided what to publish.

What that means for you:

• "Verified on hardware" means exactly that: a real run on a real console, with the log, committed under logs/. Conclusions drawn from reading source rather than running it are labelled as such.
• The AI got things wrong, and some mistakes were not cheap: bugs that froze the console, one that fataled another sysmodule at boot, a timing figure (a "119 ms" VIC blit that was really SD-card logging) published before it was checked, and an early NVENC result over-read. Every one is recorded in tier4/mitm/STATUS.md, corrections left in place.
• The history shows it. Most commits carry a Co-Authored-By: Claude trailer.

Review it as you would a contribution from someone you haven't worked with before, which is good advice for homebrew that drives hardware engines anyway.

The full log, newest first, with every dead end and its evidence, is tier4/mitm/STATUS.md. The map for picking the project up is tier4/mitm/PROJECT-HANDOFF.md; the early narrative is tier4/mitm/WRITEUP.md. The highlights:

A sysmodule can process frames at full speed; getting hold of one is the problem. Three routes through the graphics stack were each taken to a definite verdict:

The route that works goes around the graphics stack: svcDebugActiveProcess

• svcReadDebugProcessMemory, with "force_debug": true in the NPDM (as creport and dmnt.gen2 declare). mesosphere's permission check ignores the DeviceShared attribute that sank the nvmap route (kern_k_page_table_base.cpp), and a whole 1080p slot reads in ~5 ms. Two things are needed to stay attached without hurting the game:

• A debug event pump. While attached, every thread start or exit in the game suspends all its threads until the debugger continues (KDebugBase::ProcessDebugEvent). Loading screens start threads; the first stream froze on one. applet_mitm_dbgpump.cpp does what dmnt's cheat engine does: block on the debug handle, drain, continue - on the new thread's core.
• Never hold the game's graphics resources. Importing the game's buffer handle or adopting its aruid in our nvdrv session kept an exited game's memory alive, and the next launch hung on a black screen. Live mode uses only its own buffers.

The mitm sees queueBuffer when the game submits a frame, and the GPU is often still drawing it: queueBuffer carries an acquire fence, which the compositor waits on. Reading early produced torn frames and whole frames from two or three presents back. The capture now snapshots the slot and its fence together (a seqlock against the binder thread), waits for the fence (measured: 5.5 ms average in MK8D, 7.5-11 ms in BOTW), then reads. tools/sft_tool.py artifacts counts both artifacts in a recording: 29 stale / 22 torn per 3000 frames before, 0 / 0 after.

• VIC over raw nvdrv, byte-exact: SETCL is mandatory (nvservices, unlike the Linux DRM driver, does not set the class), relocs are inert on Horizon (pin with MAP_CMD_BUFFER and inline the address), the syncpoint increment must be in the command stream, and a zero address hangs the VIC and with it the compositor.
• The VIC's colour matrix, solved. Three attempts produced a flat picture; an 11-probe sweep gave an exact law (out = sum(K * in) * 2^-(8 + shift) + offset, tools/vic_csc.py) that reproduces all 528 measured values. The stream uses real BT.709 limited range.
• Block-height units differ: the VIC's is log2 of GOBs; NVENC's block_height value 2 means 16 rows. Mismatched, the encode came out perfectly scrambled.
• NVENC was never "unbooted firmware" - it was unclocked. On Horizon a client requests the engine's clock from mm:u before using it (as averne's FFmpeg nvtegra code does); an unclocked engine accepts a job and never runs it. With the clock up, the job the system's own recorder (grc) builds, captured from grc and replayed from our own channel, encodes correctly; constant QP works through RCMODE 0; error_status 2 is routine (grc's own frames carry it). P frames use grc's P setup and job with the references ping-ponging; the drift test (last frame of a 59-P-frame chain against the console's own picture) passes at 42 dB.

The last frame of a 30-frame IDR + P chain encoded on the console (Run K), decoded on the PC: 42 dB against the console's own picture of it.

The network (v0.7.0). bsd:u from a sysmodule, with a static 440 KB transfer-memory block as SysDVR's sysmodule does (libnx's default wants MB a sysmodule does not have); TCP on port 9950, one viewer; a UDP beacon on 9951. Frames go out from their own thread, so the network never stalls the capture; the QP follows how busy that thread is.

USB 2.0 bulk through usb:ds saturates at ~37 MB/s from this module (measured across five resolutions), which is why raw pixels stopped at 768x432 and the stream is H.264. Transfers that time out are cancelled, so a newly opened viewer never starts mid-frame. SuperSpeed descriptors (including the BOS usbDsSetBinaryObjectStore needs) are accepted but the link still trains to High Speed on the cable tested.

• Non-domain mitm sub-object forwarding for libstratosphere (tier4/applet-mitm/patch_libstrat.py, 55 lines): Atmosphère's mitm framework forwards undeclared commands only on domain sessions; vi:u hands out its sub-objects on non-domain ones. If you have tried to mitm vi and given up, this is the missing piece.
• A transparent vi:u mitm that recovers every frame's layout from the binder traffic (setPreallocatedBuffer, queueBuffer with its fence), and handles both GetDisplayService and GetDisplayServiceWithProxyNameExchange (command 1, used by BOTW: its request is forwarded byte for byte).
• Undocumented vi ABIs: CreateIndirectLayer (2050), CreateIndirectProducerEndPoint (2052), CreateIndirectConsumerEndPoint (2054), all {u64, u64} -> u64; GetDisplayService's command id is the service type (vi:u 0, vi:s 1, vi:m 2).
• A dmnt-style debug event pump for any sysmodule that stays attached to a game.
• PC tools with self-tests (bash tools/run_pc_tests.sh): the viewer, sft_tool.py (recording stats, drift test, artifact detector), the VIC matrix model, NVENC setup decoders.

Earlier captures, kept for the record: the game's swapchain read out at native 1080p and de-swizzled on the PC (docs/frame-1080p.png), and the raw 768x432 "packed 4:2:0" stream that preceded H.264 (docs/frame-stream-packed420.png).

The goal is the game's native docked output, 1920x1080 at 60 fps, streamed to a PC. Reached over USB (M96, Run W): 58.4 fps over a session against the game's 59.2, 59.5-59.9 fps per 20 s window once running, 0 lost or undecodable frames in 9,090. How it got there:

1. A 1080p NVENC setup (M90-M92). The system's own recorder only builds 720p jobs, so the 1080p setup was derived from grc's 720p one (tools/nvenc_replay.py). 1920x1080 stalls the engine; 1920x1088 (whole macroblock rows) encodes, and the SPS crops the picture to 1080.
2. 1080p over USB (M93). ReverseNX-RT makes the game render its docked picture in handheld, where the USB port is free; the stream detects the size change and restarts at 1080p by itself.
3. The frame budget (M94-M96). A 1080p frame is an 8.3 MB copy out of the game (~8.5 ms at CPU 1785 MHz), a 1.7 ms VIC conversion and a 5.6 ms encode. The encode now runs while the next frame is read (M94), and the capture takes the newest frame the GPU has finished instead of the newest one queued (M96: waiting on the latest queued frame skipped 20% of frames; now 1.6%).

What is left: stock clocks (1080p60 at CPU 1020 MHz). Streaming from the dock works over the network since v0.7.0, with the quality adapting to the link.

Questions, corrections, or if you want to take a piece of this further - I'd genuinely like to hear about it.

• Email: Some_Potato_1@protonmail.com
• Reddit: u/Papux200
• Issues: GitHub issues
• Forum: the GBAtemp thread

Forks are welcome and no permission is needed.

• WillMidia (PR #4): the slot matcher that finds a game's frame buffers while it streams, homebrew swapchains in larger memory blocks, the debug-event fix that kept games frozen for seconds, real crashes reaching the game's own handler, and the encoder-wait fix.
• exelix11: SysDVR, whose socket setup the network mode follows, and dvr-patches, which bring sound to games that block recording.
• Laliukz (PR #8): streaming while Atmosphère's cheat engine holds the game, through dmnt:cht.

GPL-2.0. tier4/applet-mitm links libstratosphere and ships a patch against it, so it is a derivative of Atmosphère and could not be anything else. See LICENSE and NOTICE.