Chunk header incorporating binary flags and correlated variable-length fields

A method of playing back content comprising a plurality of media frames by a playback device, where the content is stored in a media file, the method comprising:

• providing a media file having a plurality of elements that each include:
• a header, wherein the header includes a plurality of flags and data fields, the plurality of data fields includes a backward offset data field that has a pointer to a previous key-frame element, the plurality of flags includes a backward access flag that references the backward offset data field, and the previous key-frame element is arranged to be decoded independently of any other element, and
• content data comprising at least one media frame;
• decoding content data contained within elements using a playback device;
• displaying decoded content on a display;
• receiving a user request;
• identifying the header of a first element in response to the received user request;
• identifying a data field in the header of the first element that references a second element;
• retrieving the second element from the plurality of elements;
• and
• decoding one or more media frames contained in the retrieved second-element.