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• set MediaRecorder to record 1 frame every N seconds

  19 août 2022, par The Blind Hawk

  Summary

  


  I have a version of my code already working on Chrome and Edge, but I need some fixes for it to work on Safari.
  
My objective is to record around 25 minutes and download a timelapse version of the recording.
  
final product requirements :

  


  speed: 3fps
length: ~25s

(I need to record one frame every 20 seconds for 25 mins)


  


  this.secondStream settings :

  


  this.secondStream = await navigator.mediaDevices.getUserMedia({
    audio: false,
    video: {width: 430, height: 430, facingMode: "user"}
});


  


  My code for IOS so far :

  


          startIOSVideoRecording: function() {
            console.log("setting up recorder");
            var self = this;
            this.data = [];

            if (MediaRecorder.isTypeSupported('video/mp4')) {
                // IOS does not support webm, so I will be using mp4
                var options = {mimeType: 'video/mp4', videoBitsPerSecond : 1000000};
            } else {
                console.log("ERROR: mp4 is not supported, trying to default to webm");
                var options = {mimeType: 'video/webm'};
            }
            console.log("options settings:");
            console.log(options);

            this.recorder = new MediaRecorder(this.secondStream, options);

            this.recorder.ondataavailable = function(evt) {
                if (evt.data && evt.data.size > 0) {
                    self.data.push(evt.data);
                    console.log('chunk size: ' + evt.data.size);
                }
            }

            this.recorder.onstop = function(evt) {
                console.log('recorder stopping');
                var blob = new Blob(self.data, {type: "video/mp4"});
                self.download(blob, "mp4");
                self.sendMail(videoBlob);
            }

            console.log("finished setup, starting")
            this.recorder.start(1200);

            function sleep(ms) { return new Promise(resolve => setTimeout(resolve, ms));}

            async function looper() {
                // I am trying to pick one second every 20 more or less
                await sleep(500);
                self.recorder.pause();
                await sleep(18000);
                self.recorder.resume();
                looper();
            }
            looper();
        },


  


  Issues

  


  Only one call to getUserMedia()

  


  I am already using this.secondstream elsewhere, and I need the settings to stay as they are for the other functionality.
  
On Chrome and Edge, I could just call getUserMedia() again with different settings, and the issue would be solved, but on IOS calling getUserMedia() a second time kills the first stream.
  
The settings that I was planning to use (works for Chrome and Edge) :

  


  navigator.mediaDevices.getUserMedia({
    audio: false,
    video: { 
        width: 360, height: 240, facingMode: "user", 
        frameRate: { min:0, ideal: 0.05, max:0.1 } 
    },
}


  


  The timelapse library I am using does not support mp4 (ffmpeg as alternative ?)

  


  I am forced to use mp4 on IOS apparently, but this does not allow me to use the library I was relying on so I need an alternative.
  
I am thinking of using ffmpeg but cannot find any documentation to make it interact with the blob before the download.
  
I do not want to edit the video after downloading it, but I want to be able to download the already edited version, so no terminal commands.

  


  MediaRecorder pause and resume are not ideal

  


  On Chrome and Edge I would keep one frame every 20 seconds by setting the frameRate to 0.05, but this does not seem to work on IOS for two reasons.
  
First one is related to the first issue of not being able to change the settings of getUserMedia() without destroying the initial stream in the first place.
  
And even after changing the settings, It seems that setting the frame rate below 1 is not supported on IOS. Maybe I wrote something else wrong, but I was not able to open the downloaded file.
  
Therefore I tried relying on pausing and resuming the MediaRecorder, but this brings forth another two issues :
  
I am currently saving 1 second every 20 seconds and not 1 frame every 20 seconds, and I cannot find any workarounds.
  
Pause and Resume take a little bit of time, making the code unreliable, as I sometimes pick 2/20 seconds instead of 1/20, and I have no reliability that the loop is actually running every 20 seconds (might be 18 might be 25).

  


• Informations about adding image to a video

  7 juillet 2018, par J.Doe

  I’m trying to add an image to a pre-existing video in python. I haven’t write any code yet, but I’ve done some research. Most of people seem to use OpenCV or ffmpeg to manipulate image and video.
  So my questions are :

  • Can we add images to video with OpenCV or ffmpeg ?
  • Can we do that without OpenCV or ffmpeg
  • If yes, do you have some informations on it
  • If no, should I use OpenCV or ffmpeg ? Maybe another ?
  • Which version of OpenCV should I use ? and why ?
  • I’ve read that they are a problem with OpenCV and Ubuntu, did they correct it ?

  If you have some other informations or advice for me

• How to export FFMPEG into my Python program ?

  2 janvier, par user11353612

  I wrote a Python program for Windows 10 which converts audio files from any supported format to .flac, and it uses FFMPEG to do the encoding.

  



  FFMPEG is installed on my computer, so there isn't any problem when I run the program on my computer.

  



  I used PyInstaller to export my program in .exe, and now I want to include FFMPEG in the distribution so people don't have to download it separately to run my script.

  



  Can I wrap/include FFMPEG into my program, and automatically install/use it when required ? How ?