有没有办法在 google colab 中使用网络摄像头捕获实时视频？

Question

我看到 Colab 团队提供了一种通过 Colab 捕获图像的方法，但是有什么方法可以捕获视频吗？

Answer 1

最近我也在寻找答案时看到了这篇文章。我最终不得不编写自己的片段，因为我找不到任何东西。这就是我最终得到的结果，以防有帮助。该代码被分成两个单独的单元。我正在使用Python 3和Google Chrome：

from IPython.display import display, Javascript
from google.colab.output import eval_js
from base64 import b64decode

def record_video(filename='video.mp4'):

  # This function uses the take_photo() function provided by the Colab team as a  
  # starting point, along with a bunch of stuff from Stack overflow, and some sample code 
  # from: https://developer.mozilla.org/enUS/docs/Web/API/MediaStream_Recording_API

  js = Javascript("""
    async function recordVideo() {
      const options = { mimeType: "video/webm; codecs=vp9" };
      const div = document.createElement('div');
      const capture = document.createElement('button');
      const stopCapture = document.createElement("button");
      capture.textContent = "Start Recording";
      capture.style.background = "green";
      capture.style.color = "white";

      stopCapture.textContent = "Stop Recording";
      stopCapture.style.background = "red";
      stopCapture.style.color = "white";
      div.appendChild(capture);

      const video = document.createElement('video');
      const recordingVid = document.createElement("video");
      video.style.display = 'block';

      const stream = await navigator.mediaDevices.getUserMedia({video: true});
      let recorder = new MediaRecorder(stream, options);
      document.body.appendChild(div);
      div.appendChild(video);
      video.srcObject = stream;
      await video.play();

      // Resize the output to fit the video element.
      google.colab.output.setIframeHeight(document.documentElement.scrollHeight, true);

      await new Promise((resolve) => {
        capture.onclick = resolve;
      });
      recorder.start();
      capture.replaceWith(stopCapture);
      await new Promise((resolve) => stopCapture.onclick = resolve);
      recorder.stop();

      let recData = await new Promise((resolve) => recorder.ondataavailable = resolve);
      let arrBuff = await recData.data.arrayBuffer();
      stream.getVideoTracks()[0].stop();
      div.remove();

      let binaryString = "";
      let bytes = new Uint8Array(arrBuff);
      bytes.forEach((byte) => {
        binaryString += String.fromCharCode(byte);
      })
      return btoa(binaryString);
    }
    """)
  try:
    display(js)
    data = eval_js('recordVideo({})')
    binary = b64decode(data)
    with open(filename, "wb") as video_file:
      video_file.write(binary)
    print(
        f"Finished recording video. Saved binary under filename in current working directory: {filename}"
    )
  except Exception as err:
      # In case any exceptions arise
      print(str(err))
  return filename

# Run the function, get the video path as saved in your notebook, and play it back here.
from IPython.display import HTML
from base64 import b64encode

video_width = 300

video_path = record_video()
video_file = open(video_path, "r+b").read()

video_url = f"data:video/mp4;base64,{b64encode(video_file).decode()}"
HTML(f"""<video width={video_width} controls><source src="{video_url}"></video>""")

这是笔记本的链接：https://github.com/emilyxxie/colab_utils_and_snippets/blob/master/video_webcam_snippets.ipynb