Techniques for replacement content signaling in advanced television systems committee (ATSC) 3.0 television

1. A digital television system comprising:

at least one transmitter assembly comprising at least one broadcast source and at least one broadband source, the transmitter assembly comprising:

at least one processor programmed with instructions to:

generate a first media presentation description (MPD) with SegmentTimeline template comprising at least first and second Period elements, the first Period element comprising at least one segment to cause a receiver of the MPD to play media content identified by the segment, the second Period element comprising no segments in that no adaption set of the second period has references to media segments, the second Period element to cause a receiver of the MPD to fetch replaceable content or to notify a broadcaster application of replaceable content and receive instruction from the broadcaster application to cache replacement content from an indicated network address and play back the replacement content at a time corresponding to the second period.

2. The digital television system of claim 1 , wherein the second period is an extensible markup language (XML) linking language (XLink) Period element.

3. The digital television system of claim 1 , wherein the instructions are executable to:

provide the MPD from the broadcast source.

4. The digital television system of claim 1 , wherein the instructions are executable to:

provide the replacement content from the broadcast source.

5. The digital television system of claim 1 , wherein the instructions are executable to:

provide the replacement content from the broadband source.

6. The digital television system of claim 1 , wherein the instructions are executable to:

locate the second Period element at the end of the MPD.

7. The digital television system of claim 1 , wherein the instructions are executable to:

configure the second Period element to indicate a duration of the replacement content.

8. The digital television system of claim 1 , comprising the receiver.

9. A digital television system comprising:

at least one receiver comprising at least one processor programmed with instructions to configure the processor to:

receive a first media presentation description (MPD) with SegmentTimeline template comprising at least first and second Periods, the first Period comprising at least one segment and the second Period comprising no segments;

responsive to the first Period, play content according to the segment;

responsive to the second Period, execute at least one extensible markup language (XML) linking language (XLink) or signal a broadcaster application that an extensible markup language (XML) linking language (XLink) replacement content is available in future;

in response to the signal, receive from the broadcaster application a command to cache the XLink replacement content and replace the second Period with the replacement content at a time indicated by the second Period;

prior to the time indicated by the second Period, continue play of media according to the MPD; and

at the time indicated by the second Period, play the replacement content.

10. The digital television system of claim 9 , wherein the instructions are executable to:

responsive to failing to play the replacement content in the second Period, identify that the second period fills with segments until the second Period ends; and

play content indicated by the segments in the second Period.

11. The digital television system of claim 9 , wherein the instructions are executable to:

receive the MPD from a broadcast source.

12. The digital television system of claim 9 , wherein the instructions are executable to:

receive the replacement content from a broadcast source.

13. The digital television system of claim 9 , wherein the instructions are executable to:

receive the replacement content from a broadband source.

14. The digital television system of claim 9 , wherein the broadcaster application is executed by the processor of the receiver.

15. In a digital television system, a method comprising:

receiving at least one media presentation description (MPD);

responsive to a first period in the MPD containing one or more segments, playing content according to the one or more segments;

responsive to a second period in the MPD containing no segments, retrieving replacement content having a duration indicated by the second period; and

at a time indicated by the second period, playing the replacement content.

16. The method of claim 15 , comprising:

responsive to the second period, signaling to a broadcaster application that an extensible hypertext markup language link (XLink) trigger has arrived.

17. The method of claim 16 , comprising:

responsive to signaling the broadcaster application that the XLink trigger has arrived, receiving a command from the broadcaster application to retrieve the replacement content.

18. The method of claim 15 , comprising retrieving the replacement content from a broadband source.

19. The method of claim 15 , comprising retrieving the replacement content from a broadcast source.

20. The method of claim 15 , comprising receiving the MPD from a broadcast source.