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• Rolling screen capture with ffmpeg on windows

  11 décembre 2020, par gap210

  I have the following code to capture a video stream from my webcam. I use ffmpeg to write to named windows pipe, then read it with python and display with opencv. The thing is that the opencv stream is 'rolling' as shown here https://www.youtube.com/watch?v=H78TRo3DZIo

  


  If I capture the output to a video instead of a pipe, with the command :

  


  ffmpeg -f dshow -video_size 1920x1080 -framerate 60 -i video="USB Video" -c:v copy out.avi

  


  everything looks fine. What should I change to achieve the desired effect ? (non-rolling stream)

  


  My code below :

  


  import cv2
import time
import subprocess
import numpy as np

w, h = 800, 600

# Get frame generator
gen = ffmpegGrab()

# Get start time
start = time.time()

# Read video frames from ffmpeg in loop
nFrames = 0
cmd = 'C:/Users/......./Downloads/ffmpeg-4.3.1-2020-11-19-full_build/bin/ffmpeg.exe -f dshow -framerate 60 -video_size 800x600 -i video="USB Video" -pix_fmt bgr24 -vcodec rawvideo -f image2pipe -'

proc = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, shell=True, bufsize=10**9)
while True:
    # Read next frame from ffmpeg

    frame = proc.stdout.read(w * h * 3)
    frame = np.frombuffer(frame, dtype=np.uint8).reshape((h, w, 3))
    cv2.imshow('screenshot', frame)

    if cv2.waitKey(1) == ord("q"):
        break

    fps = nFrames / (time.time() - start)
    print(f'FPS: {fps}')

cv2.destroyAllWindows()


  


• why am I getting undefined for fluentffmpeg's method setFfmpegPath()

  5 décembre 2020, par Hamza J

  I am trying to build a thumbnail generator but I get an undefined error when I run the script in node js.

  


  const fluentffmpeg = require("fluent-ffmpeg");
const ffmpegPath = require("@ffmpeg-installer/ffmpeg").path;
const ffprobePath = require("@ffprobe-installer/ffprobe").path;
const fs = require("fs");

fluentffmpeg.setFfmpegPath(ffmpegPath)
console.log('fluentffmpeg.setFfmpegPath(ffmpegPath)', fluentffmpeg.setFfmpegPath(ffmpegPath))
//
fluentffmpeg.setFfprobePath(ffprobePath);
console.log('fluentffmpeg.setFfprobePath(ffprobePath)', fluentffmpeg.setFfprobePath(ffprobePath));


  


  console output :

  


  fluentffmpeg.setFfmpegPath(ffmpegPath) undefined
fluentffmpeg.setFfprobePath(ffprobePath) undefined


  


• Unexpected Exception when using ffmpeg.wasm in Chrome extension

  18 novembre 2020, par Javierd98

  I'm trying to implement a chrome extension which allows me to play flv videos by transcoding them to mp4 and then inserting a video player as it's done on the transcode example from ffmpeg.wasm.

  


  As chrome extensions don't support the execution of downloaded code, I need to use a downloaded version of ffmpeg-core.
I've downloaded the 0.8.4 version and included the folder on the manifest under web_accessible_resources, so that on the javascript file for trancoding the code is :

  


  const { createFFmpeg, fetchFile } = FFmpeg;
const ffmpeg = createFFmpeg({
  log: true,
  corePath: chrome.runtime.getURL('ffmpeg-core/ffmpeg-core.js'),
});

const transcode = async (file) => {
  const { name } = file;
  console.log('Loading ffmpeg-core.js. Transcode URL.');
  await ffmpeg.load();
  console.log('ffmpeg-core loaded.');

  let blob = await fetch(file).then(r => r.blob());
  console.log('blob downloaded');

  ffmpeg.FS('writeFile', name, blob);
  console.log('Start transcoding');
  await ffmpeg.run('-i', name,  'output.mp4');
  console.log('Complete transcoding');
  const data = ffmpeg.FS('readFile', 'output.mp4');

  const video = document.getElementById('output-video');
  video.src = URL.createObjectURL(new Blob([data.buffer], { type: 'video/mp4' }));
}


  


  Once the transcode function is executed, I get the following exception :

  


  ffmpeg.min.js:1 Uncaught (in promise) TypeError: t is not a function
    at ffmpeg.min.js:1
    at f (ffmpeg.min.js:1)
    at Generator._invoke (ffmpeg.min.js:1)
    at Generator.next (ffmpeg.min.js:1)
    at i (ffmpeg.min.js:1)
    at c (ffmpeg.min.js:1)


  


  

  


  Does somebody have any idea of why could this be happening ?

  


  Thanks a lot !