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• Best Web Video Encoding Practices for IOS (FFMpeg)

  21 juin 2012, par MagicMushroom

  I am working on an online video repository system for a client, written mostly in PHP. At the moment I am building a mobile version of our desktop website. Our desktop site allows users to watch videos in the browser, much like YouTube.

  My client uploads videos through the manager interface I have created, and my application uses FFmpeg on the server to transcode his videos into several resolutions and bitrates. I am no expert on FFmpeg, and while I do not know the ins and outs of each individual setting, I do understand how it works as a whole. Right now, we are using the mp4 container format with the h.264 codec to encode our videos. Our command looks like :

  ffmpeg -y -i "INPUT FILE.mov" -f mp4 -s 640x480 -vcodec libx264 -preset fast -maxrate 1500 -bitrate 1000 -bufsize 4096 -acodec libfaac -ab 192 -ac 2 "OUTPUT_FILE.mp4" >> "FILE.log" 2>&1 &

  I'm hoping to gain information about best practices with encoding video for web streaming on IOS and other mobile devices using FFmpeg. What resolutions and settings make for good mobile streaming video ? How can I ensure maximum compatibility across the sea of Android devices ?

• ffmpeg webcam capture a/v out of sync

  7 juillet 2014, par Cameron Ball

  I’m running this command to capture video and audio from my webcam :

  ffmpeg -y -f video4linux2 -s 320x240 -i /dev/video0 -f alsa -i "plughw:CARD=U0x46d0x825,DEV=0" -ac 2 -strict experimental Filename.mp4

  It works, but the audio is about half a second behind the video (EG if I clap, when I watch the video I’ll hear the clap and then see me do it).

  This is for an online stream, so I can’t fix it up later, it needs to be recorded correctly.

  It always seems to be off by the same amount, so I’m trying to find an option to simply delay when audio starts recording, but I can’t figure it out.

  Any ideas ?

• electron fluent-ffmpeg mergeToFile() command promise not triggering

  12 septembre 2020, par Martin

  I am trying to use fluent-ffmpeg with my electron app to concatenate multiple audio files together with an image in a video. So if i have three files :

  


  song1.mp3 1:00
song2.mp3 0:30
song3.mp3 2:00
front.jpg

  


  I could create output.mp4 which would be 3:30 seconds long, and play each file one after the other in order. With front.jpg set as the background image.

  


  I am trying to create the concatenated audio file first for this video, then I can just render a vid with two inputs ; image and the 3:30second long concatenated audio file. But I'm having difficulty getting my electron app to wait for the ffmpeg job to run and complete.

  


  I know how to do all of these ffmpeg jobs on the command-line, but I've been following this guide for how to package ffmpeg into an electron app that can run on mac/win10/linux environments. I'm developing it on win10 right now.
gur.com/LtykP.png

  


  I have a button :
<button>FULLALBUM</button>

  


  that when I click runs the fullAlbum() function that calls combineMp3FilesOrig to run the actual ffmpeg job :

  


  async function fullAlbum(uploadName) {
    //document.getElementById("buttonId").disabled = true;

    //get table
    var table = $(`#upload_${uploadNumber}_table`).DataTable()
    //get all selected rows
    var selectedRows = table.rows( '.selected' ).data()
    //get outputFile location
    var path = require('path');
    var outputDir = path.dirname(selectedRows[0].audioFilepath)
    //create outputfile
    var timestamp = new Date().getUTCMilliseconds();
    let outputFilepath = `${outputDir}/output-${timestamp}.mp3` 

    
    console.log('fullAlbum() button pressed: ', timestamp)

    await combineMp3FilesOrig(selectedRows, outputFilepath, '320k', timestamp);
    //document.getElementById("buttonId").disabled = false;

    console.log(`fullAlbum() /output-${timestamp}.mp3 should be created now`)
}

function combineMp3FilesOrig(selectedRows, outputFilepath, bitrate, timestamp) {
    console.log(`combineMp3FilesOrig(): ${outputFilepath}`)
    
    //begin get ffmpeg info
    const ffmpeg = require('fluent-ffmpeg');
    //Get the paths to the packaged versions of the binaries we want to use
    const ffmpegPath = require('ffmpeg-static').replace('app.asar','app.asar.unpacked');
    const ffprobePath = require('ffprobe-static').path.replace('app.asar','app.asar.unpacked');
    //tell the ffmpeg package where it can find the needed binaries.
    ffmpeg.setFfmpegPath(ffmpegPath);
    ffmpeg.setFfprobePath(ffprobePath);
    //end set ffmpeg info

    //create ffmpeg command
    console.log(`combineMp3FilesOrig(): create command`)
    const command = ffmpeg();
    //set command inputs
    command.input('C:\\Users\\marti\\Documents\\martinradio\\uploads\\CharlyBoyUTurn\\5. Akula (Club Mix).flac')
    command.input('C:\\Users\\marti\\Documents\\martinradio\\uploads\\CharlyBoyUTurn\\4. Civilian Barracks.flac')

    return new Promise((resolve, reject) => {
        console.log(`combineMp3FilesOrig(): command status logging`)
        command.on('progress', function(progress) {
            console.info(`Processing : ${progress.percent} % done`);
        })
        .on('codecData', function(data) {
            console.log('codecData=',data);
        })
        .on('end', function() {
            console.log('file has been converted succesfully; resolve() promise');
            resolve();
        })
        .on('error', function(err) {
            console.log('an error happened: ' + err.message, ', reject()');
            reject(err);
        })
        console.log(`combineMp3FilesOrig(): add audio bitrate to command`)
        command.audioBitrate(bitrate)
        console.log(`combineMp3FilesOrig(): tell command to merge inputs to single file`)
        command.mergeToFile(outputFilepath);
        console.log(`combineMp3FilesOrig(): end of promise`)
    });
    console.log(`combineMp3FilesOrig(): end of function`)
}


  


  When I click my button once, my console.logs show the promise is entered, the command is created, but the function just ends without waiting for a resolve() ;
Waiting a couple minutes doesnt change anything.

  


  

  


  If I press the button again :

  


  

  


  A new command gets created, reaches the end of the promise, but this time actually starts, and triggers the previous command to start. Both jobs then run and their files are rendered at the correct length (12:08) and the correct quality (320k)

  


  Is there something with my promise I need to fix involving async functions and promises in an electron app ? I tried editing my ffmpeg command to include

  


  command.run()

  


  At the end of my promise to ensure it gets triggered ; but that leads to an err in console saying Uncaught (in promise) Error: No output specified because apparently in fluent-ffmpeg command.mergeToFile(outputFilepath); isnt good enough and I need to include .output(outputFilepath) as well. If I change command.run() to command.output(outputFilepath).run(), when i click my button, the ffmpeg job gets triggered and rendered perfectly fine. EXCEPT THAT THE FILE IS ALWAYS 128kbps

  


  So I'm trying to figure out why my included code block, my ffmpeg command doesn't run the first time when its created.