Map HLS initialization and byte-range media to one resource

The useful distinctions

• EXT-X-MAP identifies the applicable initialization section.
• EXT-X-BYTERANGE identifies segment bytes within a resource.
• A byte range has a byte count and can have an explicit offset.

Draw a resource layout before a playback timeline

The synthetic object reserves its first 128 bytes for initialization metadata, followed by two 512-byte media regions. That is a byte layout, not a statement that initialization lasts 128 seconds or that each byte maps to the same amount of playback time. The media regions separately declare four seconds each. Keeping the two diagrams distinct prevents confusing storage offsets with presentation time.

Use explicit offsets for a reviewable example

Every region in this example has an explicit starting offset, so a reader can calculate the intervals independently. Initialization occupies zero through 127; the first timed region occupies 128 through 639; the second occupies 640 through 1151. A real conformant publication would need actual initialization and fragment boxes at those boundaries, as well as correct sample timing and compatible track configuration. The invented sizes have not been measured against a real container. They demonstrate internally consistent playlist declarations only. In an implementation check, validate both the container boundaries and the HTTP range responses rather than assuming correct playlist arithmetic proves either. The map occupies interval zero through just before 128, then the two declared media ranges are contiguous. These boundaries make a useful arithmetic fixture even though no valid encoded fragment is asserted to occupy them.

Worked example · synthetic

The declarations partition an invented 1152-byte layout into initialization and two timed regions. This is valid playlist syntax; no claim is made that these arbitrary byte counts contain valid MP4 boxes.

Synthetic text example; no network operation has been performed.

#EXTM3U
#EXT-X-VERSION:6
#EXT-X-PLAYLIST-TYPE:VOD
#EXT-X-TARGETDURATION:4
#EXT-X-MAP:URI="packed.mp4",BYTERANGE="128@0"
#EXTINF:4.0,
#EXT-X-BYTERANGE:512@128
packed.mp4
#EXTINF:4.0,
#EXT-X-BYTERANGE:512@640
packed.mp4
#EXT-X-ENDLIST

Check the interpretation

• Calculate end = offset + count − 1.
• Keep initialization bytes out of media-duration sums.
• Validate actual fragment boundaries when a real resource exists.