ffmpeg 在运行回调之前不等待 function 完成

Question

I'm using ffmpeg to extract some frames from a video. Unfortunatley, node js does not wait for ffmpeg to finish the task before running the callback function How do I make sure, the task has finished before running the callback?

I have been struggling with this for hours, many thanks for any help

function callback() {

console.log("All done!")
}
async function main()
{
    try {
        var process = new ffmpeg("star_wars_film_scene.mp4");
        process.then(function (video) {
            video.fnExtractFrameToJPG("frames/", {
                every_n_frames : 1500
            }), callback()
        }, function (err) {
            console.log('Error: ' + err);
        });
     } catch (e) {
        console.log(e.code);
        console.log(e.msg);
     }

    }
     


  main()

Answer 1

I can't say exactly what is going wrong with your installation. I can say that this sample code, taken directly from the ffmpeg module page (with a slight tweak to add more error handling) works just fine for me. So, if you adapt your code to work like this and make sure that both the ffmpeg module and the ffmpeg executable are properly installed, it should work:

const ffmpeg = require('ffmpeg');

try {
    const process = new ffmpeg('full path to your video here');
    process.then(function(video) {
        // Callback mode
        video.fnExtractFrameToJPG('D:/temp', {
            frame_rate: 1,
            number: 5,
            file_name: 'my_frame_%t_%s'
        }, function(error, files) {
            if (error) {
                console.log(error);
                return;
            }
            console.log('Frames: ' + files);
        });
    }, function(err) {
        console.log(err);
    });
} catch (e) {
    console.log(e.code);
    console.log(e.msg);
}

When I first ran this code on my system, I got an error because the ffmpeg executable (which was installed on my system) was not in my system path so when the ffmpeg module tried to run the ffmpeg executable, it didn't find it and it output an error message to that effect. Once I fixed that to include it in my path, it worked as it is supposed to and captured 5 frames from the video I passed it.