Controlling speed of the display of sub-titles

1. One or more non-transitory computer-readable storage mediums storing one or more sequences of instructions for applying a presentation timestamp to an element of a sequence of sub-titles, wherein execution of the one or more sequences of instructions by one or more processors causes:

initializing a minimum presentation timestamp T MIN of the element of the sequence of sub-titles N;

comparing the presentation timestamp T(N) of a new element of a sub-title sequence N and the minimum presentation timestamp for sub-titles T MIN ;

applying the minimum presentation timestamp for sub-titles T MIN to the element of the sequence of sub-titles N if the presentation timestamp T(N) of the new sub-titles element is prior to the minimum presentation timestamp for sub-titles T MIN ; and

calculating and applying the minimum presentation timestamp for sub-titles T MIN for an element of a sequence of sub-titles N+1 as a timestamp posterior to the presentation timestamp T(N) of the new sub-titles element.

2. The one or more non-transitory computer-readable storage mediums of claim 1 , wherein the minimum presentation timestamp for sub-titles T MIN is recalculated by adding a duration T MD to the presentation timestamp T(N).

3. The one or more non-transitory computer-readable storage mediums of claim 2 , wherein the duration T MD retains a fixed value.

4. The one or more non-transitory computer-readable storage mediums of claim 2 , wherein the duration T MD is dependent on the size of the sub-titles element N.

5. The one or more non-transitory computer-readable storage mediums of claim 4 , wherein the duration T MD is dependent on the number of words of the sub-titles element N.

6. The one or more non-transitory computer-readable storage mediums of claim 4 , wherein the duration T MD is dependent on the number of characters of the sub-titles element N.

7. The one or more non-transitory computer-readable storage mediums of claim 1 , wherein executing the one or more sequences of instructions further cause:

forming the element of the sequence of sub-titles N by grouping several words into a block.

8. The one or more non-transitory computer-readable storage mediums of claim 7 , wherein the block contains a sentence.

9. The one or more non-transitory computer-readable storage mediums of claim 7 , wherein the block contains a line of words.

10. The one or more non-transitory computer-readable storage mediums of claim 1 , wherein the presentation timestamp is written in a multimedia stream.

11. The one or more non-transitory computer-readable storage mediums of claim 10 , wherein the multimedia stream is an MPEG-TS stream.

12. The one or more non-transitory computer-readable storage mediums of claim 10 , wherein the multimedia stream includes a sub-titles stream according to one of the TTML norms of the W3C.

13. The one or more non-transitory computer-readable storage mediums of claim 1 , wherein the presentation timestamp of the sub-titles element is provided to a video decoder for display.

14. An apparatus for applying a presentation timestamp to an element of a sequence of sub-titles, comprising:

one or more processors; and

one or more non-transitory computer-readable storage mediums storing one or more sequences of instructions, which when executed, cause:

initializing a minimum presentation timestamp T MIN of the element of the sequence of sub-titles N;

comparing the presentation timestamp T(N) of a new element of a sub-title sequence N and the minimum presentation timestamp for sub-titles T MIN ;

applying the minimum presentation timestamp for sub-titles T MIN to the element of the sequence of sub-titles N if the presentation timestamp T(N) of the new sub-titles element is prior to the minimum presentation timestamp for sub-titles T MIN ; and

calculating and applying the minimum presentation timestamp for sub-titles T MIN for an element of a sequence of sub-titles N+1 as a timestamp posterior to the presentation timestamp T(N) of the new sub-titles element.

15. The apparatus of claim 14 , wherein the minimum presentation timestamp for sub-titles T MIN is recalculated by adding a duration T MD to the presentation timestamp T(N).

16. The apparatus of claim 15 , wherein the duration T MD retains a fixed value.

17. The apparatus of claim 15 , wherein the duration T MD is dependent on the size of the sub-titles element N.

18. The apparatus of claim 17 , wherein the duration T MD is dependent on the number of words of the sub-titles element N.

19. The apparatus of claim 17 , wherein the duration T MD is dependent on the number of characters of the sub-titles element N.

20. The apparatus of claim 14 , wherein executing the one or more sequences of instructions further cause:

forming the element of the sequence of sub-titles N by grouping several words into a block.

21. The apparatus of claim 20 , wherein the block contains a line of words or a sentence.

22. The apparatus of claim 14 , wherein the presentation timestamp is written in a multimedia stream.

23. The apparatus of claim 22 , wherein the multimedia stream is an MPEG-TS stream.

24. A method of applying a presentation timestamp to an element of a sequence of sub-titles, comprising:

executing upon hardware comprising one or more processors, initializing a minimum presentation timestamp T MIN of the element of the sequence of sub-titles N, by an encoder, transcoder, or decoder;

comparing the presentation timestamp T(N) of a new element of a sub-title sequence N and the minimum presentation timestamp for sub-titles T MIN , by the encoder, transcoder, or decoder;

applying the minimum presentation timestamp for sub-titles T MIN to the element of the sequence of sub-titles N if the presentation timestamp T(N) of the new sub-titles element is prior to the minimum presentation timestamp for sub-titles T MIN , by the encoder, transcoder, or decoder; and

calculating and applying the minimum presentation timestamp for sub-titles T MIN for an element of a sequence of sub-titles N+1 as a timestamp posterior to the presentation timestamp T(N) of the new sub-titles element, by the encoder, transcoder, or decoder.