A system for delivering live streaming content based on accurate media data fragment size and duration. The system may include a client media player to receive a portion of a streaming media file (e.g., in an MP4 format), download a first sub-portion of the streaming media file including fragment-level metadata, and parse and analyze the fragment-level metadata to determine a size and duration of a current fragment of the media file. A media server may generate custom data identifying a size and duration of a current fragment of a media file. The media server may insert the custom data (e.g., as a custom header or unique packet identifier) and send the custom data to a client media player. The client media player may be configured to decode the custom data and determine the current fragment size and duration.