[KSV]

@Liphtier

You won't find 'moov' box in client side fragments. it's not possible to accurately know the filesize before all fragments are downloaded and decoded. some websites do inject the same in metadata stored in bootstrap file but it's not necessary that the final filesize generated after decoding will match that. why don't you just try sending an arbitrary large size like some major CDN's do. for example Akamai HD streaming (over plain http) sends 2 GB as content-length header although the actual video data is normally larger or smaller than that.