Pipe and OpenCV to FFmpeg with audio streaming RTMP in Python

I’m trying to stream FFmpeg with audio.
I will show my code below:

Import module

import subprocess as sp

---

Create variables

rtmpUrl = "rtmp://a.rtmp.youtube.com/live2/key"
camera_path = "BigBuckBunny.mp4"
cap = cv.VideoCapture(camera_path)

# Get video information
fps = int(cap.get(cv.CAP_PROP_FPS))
width = int(cap.get(cv.CAP_PROP_FRAME_WIDTH))
height = int(cap.get(cv.CAP_PROP_FRAME_HEIGHT))

---

Command param

# ffmpeg command
command = ['ffmpeg',
        '-y',
        '-f', 'rawvideo',
        '-vcodec','rawvideo',
        '-pix_fmt', 'bgr24',
        '-s', "{}x{}".format(width, height),
        '-r', str(fps),
        '-i', '-',
        '-c:v', 'libx264',
        '-pix_fmt', 'yuv420p',
        '-preset', 'ultrafast',
        '-f', 'flv', 
        rtmpUrl]

---

Create subprocess to ffmpeg command

# Pipeline configuration
p = sp.Popen(command, stdin=sp.PIPE)

---

Send frame to RTMP server

# read webcamera
while(cap.isOpened()):
    ret, frame = cap.read()
    if not ret:
        print("Opening camera is failed")
        break

    # write to pipe
    p.stdin.write(frame.tobytes())

I hope you can help me to be able to live stream via FFmpeg over RTMP with audio. Thanks!

Answer

Assuming you actually need to use OpenCV for the video, you have to add the audio directly to FFmpeg as Gyan commented, because OpenCV does not support audio.

-re argument is probably required for live streaming.

---

For testing, I modified the RTMP URL from YouTube to localhost.
FFplay sub-process is used for capturing the stream (for testing).

Complete code sample:

import subprocess as sp
import cv2

#rtmpUrl = "rtmp://a.rtmp.youtube.com/live2/key"
rtmp_url = "rtmp://127.0.0.1:1935/live/test"  # Use localhost for testing
camera_path = "BigBuckBunny.mp4"
cap = cv2.VideoCapture(camera_path)

# Get video information
fps = int(cap.get(cv2.CAP_PROP_FPS))
width = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH))
height = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))

# Start the TCP server first, before the sending client (for testing).
ffplay_process = sp.Popen(['ffplay', '-listen', '1', '-i', rtmp_url])  # Use FFplay sub-process for receiving the RTMP video.

# ffmpeg command
# OpenCV does not support audio.
command = ['ffmpeg',
        '-y',
        '-re', # '-re' is requiered when streaming in "real-time"
        '-f', 'rawvideo',
        #'-thread_queue_size', '1024',  # May help https://stackoverflow.com/questions/61723571/correct-usage-of-thread-queue-size-in-ffmpeg
        '-vcodec','rawvideo',
        '-pix_fmt', 'bgr24',
        '-s', "{}x{}".format(width, height),
        '-r', str(fps),
        '-i', '-',
        '-vn', '-i', camera_path,  # Get the audio stream without using OpenCV
        '-c:v', 'libx264',
        '-pix_fmt', 'yuv420p',
        '-preset', 'ultrafast',
        # '-c:a', 'aac',  # Select audio codec
        '-bufsize', '64M',  # Buffering is probably required
        '-f', 'flv', 
        rtmp_url]

# Pipeline configuration
p = sp.Popen(command, stdin=sp.PIPE)

# read webcamera
while (cap.isOpened()):
    ret, frame = cap.read()
    if not ret:
        print("End of input file")
        break

    # write to pipe
    p.stdin.write(frame.tobytes())

p.stdin.close()  # Close stdin pipe
p.wait()

ffplay_process.kill()  # Forcefully close FFplay sub-process