HTML5 video 上传预览图片视频如何设置、预览视频某秒的海报帧

/*预览*/              $('.qtuploader__items').on('click', '[name="viewVideoPicBtn"]', function() {    var parent = $(this).closest('.qtab__page');    var video = $(this).closest('.qtuploader__itemsbd').find('video');    var srcStr = '', htmlStr = '';    if($(this).siblings('.qtuploader__picinputbox').hasClass('is-error')){      $.fn.toast({        'parentDom': parent,        'classes': 'isorange',        'top': '0',        'spacing': 0,        'toastContent': '请设置正确范围的海报帧',        'autoHide': 3000,        'position': {          'top': '5px',          'left': '50%'        }      });      return;    }    if (video.length > 0) {      var thumbHeight = setSize(video)[0];      var thumbWidth = setSize(video)[1];      srcStr = video.attr('src');      htmlStr = '<div class="qtuploader__view"><div class="qtuploader__mask"></div><div class="qtuploader__thumb" style="width:' + thumbWidth + 'px;height:' + thumbHeight + 'px;margin:0 auto;"><video controls width="' + thumbWidth + '" height="' + thumbHeight + '" src="' + srcStr + '">您的浏览器不支持 video 标签</video></div></div>';    }    parent.append(htmlStr);    parent.find('.qtuploader__view video')[0].currentTime = $(this).siblings('.qtuploader__picinputbox').find('.qtuploader__picinput').val();    parent.find('.qtuploader__view').fadeIn();  });  /*设置海报帧预览时间*/  $('.qtuploader__items').on('keyup', '.qtuploader__picinput', function() {    var parent = $(this).closest('.qtuploader__picinputbox');    var video = $(this).closest('.qtuploader__itemsbd').find('video');    var strVal = $.trim($(this).val());    console.log(strVal)    if (strVal == '') {      parent.addClass('is-error');      parent.find('.qverify__font').text('请设置海报帧');    } else if (!(/^[0-9]*$/.test(strVal))) {      parent.addClass('is-error');      parent.find('.qverify__font').text('请输入数字');    } else if (video.length > 0 && strVal > video[0].duration) {      parent.addClass('is-error');      parent.find('.qverify__font').text('不超过(' + video[0].duration + ')');      console.log('111---' + video[0].duration)    } else {      parent.removeClass('is-error');      parent.find('.qverify__font').text('请设置海报帧');    }  })  /*关闭预览*/  $(document).undelegate('.qtuploader__mask', 'click');  $(document).delegate('.qtuploader__mask', 'click', function() {    $(this).closest('.qtuploader__view').fadeOut('normal', function() {      $(this).closest('.qtuploader__view').remove();    })  })  /*设置预览大小*/  function setSize(element) {    var thumbWidth = 0, thumbHeight = 0, arr = [];    var winWidth = $(window).width(), winHeight = $(window).height();    var imgWidth = element.width(), imgHeight = element.height();    if (imgWidth > imgHeight) {      thumbHeight = parseInt(winHeight - 200);      thumbWidth = parseInt((1920 * thumbHeight) / 1080);    } else {      thumbHeight = parseInt(winHeight - 200);      thumbWidth = parseInt((1080 * thumbHeight) / 1920);    }    arr.push(thumbHeight, thumbWidth)    return arr;  }