To see this working, head to your live site.

Read video from bytes

I am writing simple REST API using Flask, which reads uploaded video and returns some JSON. Video is sent as file by POST request, with content type application/x-www-form-urlencoded.

I want to process it using opencv, but I do not know how to read it from raw binary string. The only solution I came up with, is to save video to file and read it using opencv VideoCapture class. However I would like to avoid IO operations, because I think it will slow down my API.

So my question is:

How can I transform video from raw bytes representation to opencv representation (list of numpy arrays)?

1 comment

Answers (1)

AnswerDeveloper

Jan 01

You can use the imdecode function from OpenCV to decode the raw bytes string into a numpy array:


import cv2
import numpy as np

raw_bytes = request.data  # assume this is the raw bytes string of the video file
arr = np.fromstring(raw_bytes, np.uint8)  # create a numpy array from the raw bytes
image = cv2.imdecode(arr, cv2.IMREAD_UNCHANGED)  # decode the array into an image

Then you can use the cv2.VideoCapture class to read the video frame by frame:


cap = cv2.VideoCapture(image)
while cap.isOpened():
    ret, frame = cap.read()
    if ret:
        # process the frame here
    else:
        breakcap.release()

Note that this will only work if the raw bytes string is a valid video file. If you are receiving the video in a different format (e.g. base64-encoded), you will need to first decode it into raw bytes before using imdecode.