Pi Camera

The Pi camera bridge drives Raspberry Pi cameras through libcamera: snapshots, captures into a file root, sensor controls and a shared live MJPEG stream.

Install and register

dotnet add package Shiny.AppDeviceBridge.RpiCamera

builder.UseAppDeviceBridge(
    bridge => bridge.AddRpiCameraBridge(),
    webApp => { /* … */ }
);

Client	C#	TypeScript
IRpiCameraBridge	AddRpiCameraBridgeClient()	RpiCameraBridge

Details

Raspberry Pi cameras through libcamera, with no rpicam-apps process to launch. Linux with the native shim only; everywhere else GET rpicamera says why there is no camera and the rest answer 501.

// A camera appliance is usually a headless Pi, running the bridge server with no MAUI. It chains in a MAUI app's bridge
// builder the same way.
services.AddShinyHttpServer(http => http.AddAppDeviceBridge(bridge => bridge
    .Configure(o => o.AppId = "greenhouse")
    .AddRpiCameraBridge(o =>
    {
        o.StreamWidth = 1280;
        o.StreamHeight = 720;
        o.Camera.NativeLibraryPath = "/opt/greenhouse/native";
    })));

await services.BuildServiceProvider().GetRequiredService<AppDeviceBridgeServer>().StartAsync();

• The native shim. libshinyrpi_camera.so links against libcamera’s C++ ABI, so it’s built against the libcamera the device runs: on the Pi with native/shinyrpi-camera/build.sh, or with the arm64 Dockerfile beside it. A missing or mismatched shim doesn’t stop the app; the status carries the loader’s message.
• Snapshots and captures. GET rpicamera/snapshot answers image/jpeg; POST rpicamera/capture writes the JPEG into a file root, where a transfer, a share or the files bridge picks it up. Frames are encoded on the device, from the sensor’s NV12 or YUV.
• One stream per camera. GET rpicamera/stream is multipart/x-mixed-replace MJPEG that an <img> plays directly. The camera is exclusive, so every viewer shares one session: the first viewer decides size, quality and frame rate (capped by MaxFps), a slow viewer skips to the newest frame, and a snapshot during a stream comes from it. The session closes when the last viewer leaves, MaxStreamDuration ends a viewer that never does, and DELETE rpicamera/streams ends them all.
• Controls. GET rpicamera/controls lists what the attached sensor accepts; PUT applies values to a running stream and to every session opened after. A control the sensor lacks is a 400 unsupported_control: a Camera Module 3 has autofocus, a v2 doesn’t.
• Busy. Another process holding the camera (rpicam-still, say) is a 409 camera_unavailable.

<img src="_bridge/rpicamera/stream?fps=10" />

const camera = new RpiCameraBridge();
const photo = await camera.capture({ root: "data", path: "photos/now.jpg" });
await camera.setControls({ values: [{ control: "Brightness", value: 0.2 }] });

Into a stream

A Bluetooth LE L2CAP channel has no HTTP to carry multipart/x-mixed-replace, so ICameraService.StreamToAsync writes the feed into any System.IO.Stream — an L2CAP channel above all, but a socket or a file works too — and a viewer reads it back with ReadFramesAsync. It isn’t a bridge route: the app calls it on the ICameraService that AddRpiCameraBridge() registers. Linux with the native shim, like the rest; everywhere else it throws CameraUnavailableException before touching the stream.

// On the Pi (Shiny.BluetoothLE.Hosting 5.6.5+): the ticket's PSM and token go to the phone over a route it already trusts,
// such as a GATT command. The handler runs once the phone's channel presents the token.
var ticket = await broker.Reserve("camera", TimeSpan.FromSeconds(30), (channel, ct) =>
    camera.StreamToAsync(channel, new RpiCameraStreamSettings { MaxFps = 8 }, cancellationToken: ct));

// On the phone (Shiny.BluetoothLE 5.6.5+, Shiny.AppDeviceBridge.RpiCamera.Client)
await using var channel = await peripheral.OpenL2CapTicketChannel(psm, token);
await foreach (var frame in channel.ReadFramesAsync())
    preview.Source = ImageSource.FromStream(() => new MemoryStream(frame.Jpeg));

• The format. Every frame is a 28-byte little-endian header — payload length (u32), sequence (u32), width (u32), height (u32), FourCC MJPG (u32), timestamp in milliseconds (i64) — then that many bytes of JPEG. The sequence is the sensor’s counter, so a gap is frames the device dropped and a widening one says to ask for less; the timestamp is the device’s monotonic clock, not wall time. RpiCameraFrameStream in Shiny.AppDeviceBridge.RpiCamera.Client holds the format for either end: ReadFramesAsync yields RpiCameraStreamFrames, WriteFrameAsync writes one, and WriteHeader / TryReadHeader work with an RpiCameraFrameHeader directly.
• How it ends. The stream closing between frames ends ReadFramesAsync quietly. Closing part way through a frame is an EndOfStreamException, and a header claiming an empty frame or more than MaxFrameBytes (8 MB) is an InvalidDataException — a reader sizes a buffer from it, so it isn’t believed.
• Settings. RpiCameraStreamSettings: CameraId, Width × Height (640 × 480), Quality (60), MaxFps (10), MaxDuration (5 minutes) and LimitedRangeInput. Frames beyond MaxFps are dropped before they’re encoded, which is where a Pi’s CPU goes; a pipeline already producing MJPEG passes its frames straight through. MaxDuration is always there, because a viewer that walks out of range never says stop.
• Opened on connect. The camera session opens when StreamToAsync starts and is released when it returns, so call it once a viewer has actually connected. A slow destination backs up into the writes, and frames produced meanwhile are skipped rather than queued. The session is its own, not the bridge’s shared one: it isn’t listed by GET rpicamera, DELETE rpicamera/streams doesn’t end it, and the camera is exclusive either way.
• Ending and progress. It returns RpiCameraStreamEnd.CameraStopped or MaxDurationReached; cancelling throws OperationCanceledException, and a viewer that went away is an IOException. The destination is never disposed. Pass an RpiCameraStreamStatistics to read FramesSent, FramesDropped and BytesSent from another thread while it runs.

Requests

GET/_bridge/rpicameraWhether a camera backend loaded, the cameras attached, and the streams running.GET/_bridge/rpicamera/snapshotA JPEG from the camera.POST/_bridge/rpicamera/captureTakes a photograph and writes it into a file root, where the page, a transfer or a share can pick it up.GET/_bridge/rpicamera/controlsEvery control, what the sensor accepts, and the value the bridge applies.PUT/_bridge/rpicamera/controlsSets controls on a running stream and on every session opened later.DELETE/_bridge/rpicamera/streamsEnds every stream, closing each viewer's response and releasing the cameras.

GET/_bridge/rpicamera#

Whether a camera backend loaded, the cameras attached, and the streams running.

C#IRpiCameraBridge.GetStatusAsyncTSRpiCameraBridge.getStatus

Response

200 RpiCameraStatus

RpiCameraStatus · 4 fields

supported	boolean	False off Linux, without libcamera, or with the native shim missing — backend says which.
backend	string	The backend and the libcamera it was built against, or why there is none.
cameras	RpiCameraInfo[]	Every camera attached. Empty isn't an error: a badly seated ribbon cable looks like this.
streams	RpiCameraStream[]	Streams running now.

GET/_bridge/rpicamera/snapshot#

A JPEG from the camera. Taken from the running stream when there is one, otherwise from a session opened for the photograph. Fails with 404 for an unknown camera and 409 while another process holds the camera.

C#IRpiCameraBridge.SnapshotAsyncTSRpiCameraBridge.snapshot

Parameter	In	Type
camera	query	string | null	optional
width	query	number	optional
height	query	number	optional
quality	query	number	optional

Response

200 Binary content — Blob in TypeScript, Stream / byte[] in C#

Errors

404Not found409Conflict

POST/_bridge/rpicamera/capture#

Takes a photograph and writes it into a file root, where the page, a transfer or a share can pick it up.

C#IRpiCameraBridge.CaptureAsyncTSRpiCameraBridge.capture

Body

application/json · RpiCameraCapture

RpiCameraCapture · 6 fields

root	string	The file root, as the files bridge names it.
path	string	Where in the root. An existing file is replaced.
cameraId	string | null	Null takes the first camera.
width	number	Zero takes the bridge's still size.
height	number
quality	number	JPEG quality, 1 to 100; zero takes the bridge's still quality.

Response

200 FileEntry

FileEntry · 5 fields

name	string	The entry's name; the root's name for the root itself.
path	string	Relative to the root, with forward slashes. Empty for the root.
isDirectory	boolean	Whether it is a directory.
size	number | null	Bytes, for files.
modified	string	When it last changed.

GET/_bridge/rpicamera/controls#

Every control, what the sensor accepts, and the value the bridge applies.

C#IRpiCameraBridge.GetControlsAsyncTSRpiCameraBridge.getControls

Parameter	In	Type
camera	query	string | null	optional

Response

200 RpiCameraControlInfo[]

RpiCameraControlInfo · 6 fields

control	RpiCameraControl
supported	boolean	False when the attached sensor doesn't have the control.
minimum	number
maximum	number
default	number
value	number | null	The value the bridge applies to every session it opens; null when it leaves the sensor's own.

PUT/_bridge/rpicamera/controls#

Sets controls on a running stream and on every session opened later. Fails with 400 naming a control the sensor lacks.

C#IRpiCameraBridge.SetControlsAsyncTSRpiCameraBridge.setControls

Parameter	In	Type
camera	query	string | null	optional

Body

application/json · RpiCameraControlsInput

RpiCameraControlsInput · 1 field

values

RpiCameraControlValue[]

Response

200 RpiCameraControlInfo[]

RpiCameraControlInfo · 6 fields

control	RpiCameraControl
supported	boolean	False when the attached sensor doesn't have the control.
minimum	number
maximum	number
default	number
value	number | null	The value the bridge applies to every session it opens; null when it leaves the sensor's own.

Errors

400Bad request

DELETE/_bridge/rpicamera/streams#

Ends every stream, closing each viewer's response and releasing the cameras.

C#IRpiCameraBridge.StopStreamsAsyncTSRpiCameraBridge.stopStreams

Response

204 No content

Events

This bridge raises no events — everything it does is a request and its response.

Types

JSON property names are camelCase and enums travel as their names. A ? marks a property the payload may omit;| null one that may be null.

RpiCameraStatusobject#

What the camera can do here.

supported	boolean	False off Linux, without libcamera, or with the native shim missing — backend says which.
backend	string	The backend and the libcamera it was built against, or why there is none.
cameras	RpiCameraInfo[]	Every camera attached. Empty isn't an error: a badly seated ribbon cable looks like this.
streams	RpiCameraStream[]	Streams running now.

RpiCameraInfoobject#

A camera attached to the device.

id	string	Stable across reboots, but not across a move to another CSI port.
model	string	The sensor, such as imx708; empty when it doesn't say.
maxWidth	number	The full width of the sensor's pixel array.
maxHeight	number
rotationDegrees	number	How the sensor is mounted.
location	RpiCameraLocation

RpiCameraLocationenum#

"External""Front""Back"

RpiCameraStreamobject#

A live stream, shared by everyone watching it.

cameraId	string
width	number	What the camera actually delivers, which may differ from what was asked for.
height	number
pixelFormat	string	The sensor's format as a FourCC, such as NV12; frames are encoded to JPEG from it.
quality	number
maxFps	number
viewers	number	Open stream responses.
framesDelivered	number
framesDropped	number	Frames the camera produced faster than they could be sent.

RpiCameraCaptureobject#

A photograph to take and write into a file root.

root	string	The file root, as the files bridge names it.
path	string	Where in the root. An existing file is replaced.
cameraId?	string | null	Null takes the first camera.
width?	number	Zero takes the bridge's still size.
height?	number
quality?	number	JPEG quality, 1 to 100; zero takes the bridge's still quality.

FileEntryobject#

A file or directory.

name	string	The entry's name; the root's name for the root itself.
path	string	Relative to the root, with forward slashes. Empty for the root.
isDirectory	boolean	Whether it is a directory.
size	number | null	Bytes, for files.
modified	string	When it last changed.

RpiCameraControlInfoobject#

control	RpiCameraControl
supported	boolean	False when the attached sensor doesn't have the control.
minimum	number
maximum	number
default	number
value	number | null	The value the bridge applies to every session it opens; null when it leaves the sensor's own.

RpiCameraControlenum#

A sensor control. Which ones exist depends on the module: a Camera Module 3 has autofocus, a v2 doesn't.

"AutoExposure""ExposureTime""AnalogueGain""AutoWhiteBalance""WhiteBalanceMode""Brightness""Contrast""Saturation""Sharpness""ExposureValue""FrameDurationMin""FrameDurationMax""AutoFocusMode""LensPosition""NoiseReduction"

RpiCameraControlsInputobject#

Control values to apply now, to a running stream, and to every session opened later.

values

RpiCameraControlValue[]

RpiCameraControlValueobject#

control	RpiCameraControl
value	number | null	Null goes back to the sensor's own value from the next session.

Security

These routes sit under AppDeviceBridgePolicies.Bridges like every other bridge: callers on this device by default. See Security.