How to automatically play an mp4 uploaded in flask app

I have a flask app with an upload button for videos (mp4), and I am trying to figure out how to get the video to play on the screen after upload. Currently, it opens a generic gray video screen, but no video plays. I am including portions of my and index.html files below. I also have a predict button that I would like to be able to interact with while the video continues to play.

I would appreciate any suggestions for how to accomplish this.

@app.route('/', methods=['GET'])
def index():
    # Main page
    return render_template('index.html')

@app.route('/predict', methods=['GET', 'POST'])
def upload():
    if request.method == 'GET':
        return render_template('index.html')

    if request.method == 'POST':
        # Get the file from post request
        f = request.files['file']
        # Save the file to ./uploads
        basepath = os.path.dirname(__file__)
        file_path = os.path.join(
            basepath, 'static', secure_filename(f.filename))

        result = model_predict(file_path, model)

        return jsonify(result)

    return None

if __name__ == '__main__':
    #, debug=True)

    # Serve the app with gevent
    http_server = WSGIServer(('', 5000), app)


    <form id="upload-file" method="post" enctype="multipart/form-data">
        <label for="imageUpload" class="upload-label">
            Upload (mp4)
        <input type="file" name="file" id="imageUpload" accept=".mp4">

    <div class="image-section" style="display:none;">
        <div class="img-preview">
            <div id="imagePreview">

<video controls width="500" style="center">

    <source src="{{url_for('static', filename=f)}}" type="video/mp4" autoplay>
    Sorry, your browser doesn't support embedded videos.


<input type="file" name="file[]" class="file_multi_video" accept="video/*">
            <button type="button" class="btn btn-primary btn-lg " id="btn-predict">Identify</button>

    <div class="loader" style="display:none;"></div>

    <h3 id="result">
        <span> </span>