convert yuv420p raw data to image opencv

Question

I have raw data from rtmp server with pixel format yuv420p

I use pipe to read data. But I don't know how to decode raw data to image.

command = ['ffmpeg']
command.extend(["-loglevel", "fatal", "-i", 'rtmp://localhost/live/stream', "-f", "flv", "-pix_fmt" , 'yuv420p', '-vcodec', 'h264', "-"])
self.process = subprocess.Popen(command, stderr=subprocess.PIPE ,stdout = subprocess.PIPE)
self.output = self.process.stdout
self.fs = width*height*3 // 2
while True:
    data = self.output.read(self.fs)

I have try decode like this enter link description here

But result is enter image description here

Can anyone help me with this problem ?

Answer 1

I am no expert on ffmpeg, so I will defer to anybody who knows better and delete my answer if it proves incorrect.

As far as I can see, you have an RTMP stream that you want to ingest into OpenCV. OpenCV uses Numpy arrays with BGR ordering to store images - and video frames obviously, which are just lots of images one after the other. So, I would suggest you ask ffmpeg to convert the Flash video stream to exactly what OpenCV wants:

ffmpeg <RTMP INPUT STUFF> -pix_fmt bgr24 -f rawvideo -

and then change this since it is now BGR888:

self.fs = width * height * 3

---

As I don't have an RTMP source available, I generated a test stream like this:

# Generate raw video stream to read into OpenCV    
ffmpeg -f lavfi -i testsrc=duration=10:size=640x480:rate=30 -pixel_format rgb24 -f rawvideo -

And then I piped that into Python with:

ffmpeg -f lavfi -i testsrc=duration=10:size=640x480:rate=30 -pixel_format rgb24 -f rawvideo - | ./PlayRawVideo

The Python program PlayRawVideo looks like this:

#!/usr/bin/env python3

import numpy as np
import cv2
import sys

# Set width and height
w, h = 640, 480

while True:
    data = sys.stdin.buffer.read(w * h *3)
    if len(data) == 0:
        break
    frame = np.frombuffer(data, dtype=np.uint8).reshape((h, w, 3))
    cv2.imshow("Stream", frame)
    cv2.waitKey(1)
    

Note that I had to use sys.stdin.buffer.read() to get raw binary data.