Camera

redroid devices have no camera of their own. Sessions on Android 13, 14 and 15 get one from Holtdroid: a back camera that any app can open (Camera2, CameraX, a WebView’s getUserMedia). The Camera card on the session page chooses what it shows.

Source	What apps see
Test card	SMPTE color bars with the date and a running clock, the default
No picture	A black frame, as from a covered lens
A media file	An image (a QR code, a document, a face) or a video from your media library, on repeat
Your camera	This browser’s camera, live, for as long as you keep it on

The clock on the test card shows at a glance whether the picture an app got is live, frozen or late. Images and videos are scaled to fill the frame the app asked for and cut at the center, so any aspect ratio works; the picture is upright on a phone held in portrait, as with a real back camera.

The card says in use while an app has the camera open. Your camera asks for the browser’s permission the first time, sends 15 frames a second (about 3–7 Mbit/s up) and stops when you close the session page or pick another source.

Media library

Images and videos come from the same library as the microphone’s files: add them from either card. Each user has media.quota (5 GiB by default).

Load

Nothing renders while no app uses the camera: the agent makes frames only for an open camera. On Android 15 the camera HAL itself starts when an app opens the camera and exits a few seconds after it closes it; on 13 and 14 it stays up but idle (about 16 MB of memory, no CPU), because their cameraserver can’t cope with a stopped one. While one is open, a 1080p stream costs about a third of a CPU core (ffmpeg making the picture and the HAL copying it into the app’s buffers).

How it works

holtdroid-redroid’s images for Android 13 to 15 carry a small camera HAL (an AIDL camera provider, lazy on 15). When an app configures a stream it connects to the agent over the abstract socket @holtdroid-camera, asks for the largest stream’s size and reads raw frames that ffmpeg renders from the chosen source; it scales them into each of the app’s buffers and encodes JPEGs for still captures on the CPU, without the GPU. Android 11 and 12, and phones, have no Holtdroid camera, and the card is not shown.