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• How can I create a side-by-side horizontally stacked video with a delay in video and audio using ffmpeg-python ?

  3 septembre 2021, par kup

  I am trying to create a video from two videos that will be stacked horizontally, but the resulting video is not what I expected. The same video is appearing on both sides (left and right). How can that be achieved ?

  


  The ffmpeg command I tried, which kind of worked :

  


  ffmpeg -i left.mp4 -i right.mp4 -filter_complex "
[0:v]setpts=PTS-STARTPTS[l];
[1:v]setpts=PTS-STARTPTS,tpad=start_duration=14:start_mode=add:color=black[r];
[l][r]hstack=inputs=2[stacked]; [0:a][1:a]amix=inputs=2[a]
" -map "[stacked]" -map "[a]" -c:a aac -preset superfast result.mp4


  


  The ffmpeg-python script that's not working :

  


  in0 = ffmpeg.input('0.mp4')
in1 = ffmpeg.input('right.mkv')
aout = ffmpeg.filter([in0.audio, in1.audio.filter('adelay', "5000|5000")],'amix')
vout = ffmpeg.filter([inv0.video, inv1.video.filter('tpad', start_duration=5, start_mode='add', color='black')], 'hstack')

(
    ffmpeg
    .concat(vout, aout, v=1, a=1)
    .output("out.mkv")
    .run()
)


  


  This script is not resulting in the expected output which is two videos side-by-side horizontally stacked.

  


• How can I stream a video from localhost to web browser using the video tag ?

  3 septembre 2021, par kup

  Basically what I want to stream a video to my browser both on localhost, using Flask, OpenCV, or FFmpeg.

  


  But I am not sure how to do it.

  


  I tried this :

  


  #!/usr/bin/env python
from flask import Flask, render_template, Response
import cv2
import sys
import numpy

app = Flask(__name__)

def get_frame():
    c=cv2.VideoCapture("output.mkv")

    while True:
        retval, im = c.read()
        imgencode=cv2.imencode('.jpg',im)[1]
        stringData=imgencode.tostring()
        yield (b'--frame\r\n'
            b'Content-Type: text/plain\r\n\r\n'+stringData+b'\r\n')

    del(c)

@app.route('/vid')
def vid():
     return Response(get_frame(),mimetype='multipart/x-mixed-replace; boundary=frame')


if __name__ == '__main__':
    app.run(host='localhost',port=5000, debug=True, threaded=True)


  


  But it's not working. Maybe because it is sending images. How can I stream video ?

  


• Gstreamer, x264enc "Redistribute latency..." error

  20 août 2021, par Jason

  I'm trying to setup a video pipeline with very limited bandwidth. I was able to do it with two raspberry pis using the below lines. The first is for the camera pi and the second is to watch stream :

  


  gst-launch-1.0 rpicamsrc preview=false !  'video/x-h264, width=800, height=600, framerate=30/1' ! h264parse ! rtph264pay config-interval=1 pt=96 ! gdppay ! udpsink host=YOUR_PC_IP port=5000
gst-launch-1.0 udpsrc port=5000 ! gdpdepay ! rtph264depay ! h264parse ! avdec_h264 ! autovideosink sync=false


  


  It works but I go over my bandwidth limit if there is movement. I'm not sure if there is a way to limit bandwidth by setting a parameter here :

  


  'video/x-h264, width=800, height=600, framerate=30/1'


  


  From what I can find online, I have to use something like x264enc. I've followed tutorials but I can't get x264enc to work. it always outputs "Redistribute latency..." on both machines when run and it stays there.

  


  I've tried using x264enc like follows :

  


  gst-launch-1.0 rpicamsrc preview=false !  'video/x-raw, width=800, height=600, framerate=30/1' ! x264enc ! h264parse ! rtph264pay config-interval=1 pt=96 ! gdppay ! udpsink host=YOUR_PC_IP port=5000
gst-launch-1.0 rpicamsrc preview=false !  'video/x-raw, width=800, height=600, framerate=30/1' ! x264enc tune=zerolatency ! h264parse ! rtph264pay config-interval=1 pt=96 ! gdppay ! udpsink host=YOUR_PC_IP port=5000
gst-launch-1.0 rpicamsrc preview=false ! x264enc ! h264parse ! rtph264pay config-interval=1 pt=96 ! gdppay ! udpsink host=YOUR_PC_IP port=5000
gst-launch-1.0 rpicamsrc preview=false ! x264enc tune=zerolatency ! h264parse ! rtph264pay config-interval=1 pt=96 ! gdppay ! udpsink host=YOUR_PC_IP port=5000


  


  Based on tutorials, I would think some of those should work. Other threads say that tune=zerolatency fixes my problem. At least the ones with same output of "Redistribute latency..." I don't know what I'm doing wrong.

  


  Any help would be appreciated. Thanks !