javascript - 带有 JavaScript 的 ffmpeg 缩略图

Question

我正在使用下面的代码从视频中生成缩略图。
它生成一张 4 帧的图像。问题是它不在帧之间寻找，所以 4 帧是相同的。我想我必须使用 select而不是 -ss但我不知道怎么做。

// - inPath: path to video file
// - outPath: path to thumbnail, no thumbnail will be generated when absent
// - count: number of thumbs to generate
self.exec = function (inPath, outPath, count, handler) {
    var args = outPath ? [
        '-i', inPath ,
        '-f', 'image2',
        '-vframes', count || 1,
        '-aspect', '4:3',
        '-filter:vf', 'scale=\'if(gt(a,4/3),128,-1)\':' + 
           '\'if(gt(a,4/3),-1,96)\',' + 
           'pad=w=128:h=97:x=(ow-iw)/2:y=(oh-ih)/2:color=black,tile=4x1',
        '-y',
        '-ss', '15',
        outPath
    ] : [
        '-i', inPath
    ];

Answer 1

我有这个工作。

mdata = ffprobe(function(metadata){ },inPath)

        var parts = mdata['duration'].split(":");
        var hours = parts[0];
        var minutes = parts[1];
        var seconds = parts[2];
        var durationSec = 3600 * parseFloat(hours) + 60 * parseFloat(minutes) + parseFloat(seconds);

        var distance = Math.round(durationSec/5);       

        var args = outPath ? [
            '-ss', distance ,
            '-i', inPath ,
            '-f', 'image2',
            '-vframes', count || 1,
            '-aspect', '4:3',
            '-filter:vf', 'select=\'isnan(prev_selected_t)+gte(t-prev_selected_t\\,'+ distance +')\',' + 'scale=\'if(gt(a,4/3),206,-1)\':' + 
            '\'if(gt(a,4/3),-1,154)\',' + 
            'pad=w=206:h=155:x=(ow-iw)/2:y=(oh-ih)/2:color=black,tile=4x1',
            '-y',



            outPath
        ] : [
            '-i', inPath
        ];