How to load video in Opencv from byte string?

Question

Python

How can one read a byte string in cv2.VideoCapture? I tried like this:

cap = cv2.VideoCapture(io.BytesIO(decoded_vid)) # decoded_vid - bytes

When doing this I get a TypeError:

TypeError: Argument 'index' is required to be an integer

This seems to be a very popular use case, but I haven't been able to find examples of detailed work. It's still not quite clear why it expects an int argument - even the official doc has examples where a string with a file path is passed as an argument.

Full traceback:

ff_videocomp_1   |   File "/usr/local/lib/python3.8/site-packages/uvicorn/protocols/http/httptools_impl.py", line 390, in run_asgi
ff_videocomp_1   |     result = await app(self.scope, self.receive, self.send)
ff_videocomp_1   |   File "/usr/local/lib/python3.8/site-packages/uvicorn/middleware/proxy_headers.py", line 45, in __call__
ff_videocomp_1   |     return await self.app(scope, receive, send)
ff_videocomp_1   |   File "/usr/local/lib/python3.8/site-packages/fastapi/applications.py", line 179, in __call__
ff_videocomp_1   |     await super().__call__(scope, receive, send)
ff_videocomp_1   |   File "/usr/local/lib/python3.8/site-packages/starlette/applications.py", line 111, in __call__
ff_videocomp_1   |     await self.middleware_stack(scope, receive, send)
ff_videocomp_1   |   File "/usr/local/lib/python3.8/site-packages/starlette/middleware/errors.py", line 181, in __call__
ff_videocomp_1   |     raise exc from None
ff_videocomp_1   |   File "/usr/local/lib/python3.8/site-packages/starlette/middleware/errors.py", line 159, in __call__
ff_videocomp_1   |     await self.app(scope, receive, _send)
ff_videocomp_1   |   File "/usr/local/lib/python3.8/site-packages/starlette/exceptions.py", line 82, in __call__
ff_videocomp_1   |     raise exc from None
ff_videocomp_1   |   File "/usr/local/lib/python3.8/site-packages/starlette/exceptions.py", line 71, in __call__
ff_videocomp_1   |     await self.app(scope, receive, sender)
ff_videocomp_1   |   File "/usr/local/lib/python3.8/site-packages/starlette/routing.py", line 566, in __call__
ff_videocomp_1   |     await route.handle(scope, receive, send)
ff_videocomp_1   |   File "/usr/local/lib/python3.8/site-packages/starlette/routing.py", line 227, in handle
ff_videocomp_1   |     await self.app(scope, receive, send)
ff_videocomp_1   |   File "/usr/local/lib/python3.8/site-packages/starlette/routing.py", line 41, in app
ff_videocomp_1   |     response = await func(request)
ff_videocomp_1   |   File "/usr/local/lib/python3.8/site-packages/fastapi/routing.py", line 182, in app
ff_videocomp_1   |     raw_response = await run_endpoint_function(
ff_videocomp_1   |   File "/usr/local/lib/python3.8/site-packages/fastapi/routing.py", line 133, in run_endpoint_function
ff_videocomp_1   |     return await dependant.call(**values)
ff_videocomp_1   |   File "./main.py", line 26, in process
ff_videocomp_1   |     cap = cv2.VideoCapture(io.BytesIO(decoded_vid))
ff_videocomp_1   | TypeError: Argument 'index' is required to be an integer

Answer 1

1. We open the dock and read what VideoCapture takes as a parameter, so that it is "quite clear"
2. We publish the full traceback of errors, otherwise they are often not about what the questioner thinks about.