[Question] Webcam through FastAPI

[jiang131072]

Question

Using FastAPI and Flet to access WebCAM. The Image flickering.
Is that the intended behavior ?

I'm on Archlinux KDE (GTK backend).

Code sample

# server
from contextlib import asynccontextmanager

import cv2 as cv
from fastapi import FastAPI, Response

cap = cv.VideoCapture()


@asynccontextmanager
async def lifespan(app: FastAPI):
    cap.open(0)
    yield
    cap.release()


app = FastAPI(lifespan=lifespan)


@app.get("/frame")
def grab_video_frame() -> Response:
    _, frame = cap.read()
    _, jpeg = cv.imencode(".jpg", frame)
    return Response(content=jpeg.tobytes(), media_type="image/jpeg")


if __name__ == "__main__":
    import uvicorn

    uvicorn.run(app, log_level="critical")

# client
import time

import flet as ft

FRAME_RATE = 12


class LiveImage(ft.Image):
    def did_mount(self):
        while True:
            self.update_frame()
            time.sleep(1 / FRAME_RATE)

    def update_frame(self):
        self.src = f"http://localhost:8000/frame?{time.time()}"
        self.update()


def main(page: ft.Page):
    page.add(ft.Row([LiveImage()]))


if __name__ == "__main__":
    ft.app(target=main)

Error message

No response

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• I have searched for answers to my question both in the issues and in previous discussions.

[ndonkoHenri]

Try setting Image.gapless_playback to True (ref).
So in your case:

class LiveImage(ft.Image):
    def __init__(self):
        super().__init__(gapless_playback=True)
        # OR
        # self.gapless_playback = True
    def did_mount(self):
        ...