No duration data after convert

[alvisecastagna1]

Good afternoon,
i'm try to detect the video duration but after finished converting there are no duration data in blob file.

Here the option code:

var options = {
controls: true,
fluid: false,
plugins: {
record: {
audio: true,
video: {
mandatory: {
minWidth: 1280,
minHeight: 720,
},
},
frameWidth: 1920,
frameHeight: 1080,
videoMimeType: 'video/webm;codecs=H264',
maxLength: 100,
debug: true,
convertEngine: 'ts-ebml'
}
}
};