Use of steganographically-encoded time information as basis to establish a time offset, to facilitate taking content-related action

1. A method comprising:

receiving by a client an ongoing media stream that includes a watermark steganographically encoding a timestamp of a portion of the media stream;

extracting by the client the timestamp from the watermark;

computing by the client a time offset based on a comparison of the extracted timestamp with client-time according to a clock of the client; and

using by the client the computed time offset as a basis to control when the client will carry out a content-related action in the media stream.

2. The method of claim 1 , wherein computing the time offset based on the comparison of the extracted timestamp with the client-time comprises computing the time offset as a difference between the extracted timestamp and the client-time.

3. The method of claim 1 ,

wherein the watermark is a first watermark, the timestamp is a first timestamp, the portion is a first portion, the comparison is a first comparison, and the client-time is a first client-time, and wherein the media stream further includes a second watermark encoding a second timestamp of a second portion of the media stream, the method further comprising:

extracting by the client the second timestamp from the second watermark,

wherein computing the time offset based on the first comparison of the first extracted timestamp with the first client-time according to the clock of the client comprises computing the time offset based on (i) the first comparison and (ii) a second comparison of the extracted second timestamp with a second client-time according to the clock of the client.

4. The method of claim 1 , wherein the content-related action comprises dynamic content modification.

5. The method of claim 1 , wherein the content-related action comprises dynamic ad replacement.

6. The method of claim 1 , further comprising:

receiving by the client a directive for the client to carry out the content-related action in the media stream, the directive specifying an action time point when the client should carry out the content-related action,

wherein using by the client the computed time offset as a basis to control when the client will carry out the content-related action in the media stream comprises applying the computed time offset as a basis to translate the specified action time point into an associated client-time point according to the clock of the client.

7. The method of claim 1 , further comprising:

generating query fingerprints representing the media stream; and

transmitting, from the client to a server, the generated query fingerprints to enable the server to identify the media stream.

8. A media client comprising:

a content input interface;

a content presentation interface;

a processing unit;

non-transitory data storage; and

program instructions stored in the non-transitory data storage and executable by the processing unit to carry out operations including:

receiving an ongoing media stream that includes a watermark steganographically encoding a timestamp of a portion of the media stream,

extracting the timestamp from the watermark,

computing a time offset based on a comparison of the extracted timestamp with client-time according to a clock of the media client, and

using the computed time offset as a basis to control when the media client will carry out a content-related action in the media stream.

9. The media client of claim 8 , wherein computing the time offset based on the comparison of the extracted timestamp with the client-time comprises computing the time offset as a difference between the extracted timestamp and the client-time.

10. The media client of claim 8 ,

wherein the watermark is a first watermark, the timestamp is a first timestamp, the portion is a first portion, the comparison is a first comparison, and the client-time is a first client-time, and wherein the media stream further includes a second watermark encoding a second timestamp of a second portion of the media stream, the operations further including:

extracting the second timestamp from the second watermark,

wherein computing the time offset based on the first comparison of the first extracted timestamp with the first client-time according to the clock of the media client comprises computing the time offset based on (i) the first comparison and (ii) a second comparison of the extracted second timestamp with a second client-time according to the clock of the media client.

11. The media client of claim 8 , wherein the content-related action comprises dynamic content modification.

12. The media client of claim 8 , wherein the content-related action comprises dynamic ad replacement.

13. The media client of claim 8 , wherein the operations further include:

receiving a directive for the media client to carry out the content-related action in the media stream, the directive specifying an action time point when the media client should carry out the content-related action,

wherein using the computed time offset as a basis to control when the media client will carry out the content-related action in the media stream comprises applying the computed time offset as a basis to translate the specified action time point into an associated client-time point according to the clock of the media client.

14. The media client of claim 8 , wherein the media client is a television.

15. Non-transitory data storage having stored program instructions executable by at least one processor to cause a media client to carry out operations comprising:

receiving an ongoing media stream that includes a watermark steganographically encoding a timestamp of a portion of the media stream;

extracting the timestamp from the watermark;

computing a time offset based on a comparison of the extracted timestamp with client-time according to a clock of the media client; and

using the computed time offset as a basis to control when the media client will carry out a content-related action in the media stream.

16. The non-transitory data storage of claim 15 , wherein computing the time offset based on the comparison of the extracted timestamp with the client-time comprises computing the time offset as a difference between the extracted timestamp and the client-time.

17. The non-transitory data storage of claim 15 ,

wherein the watermark is a first watermark, the timestamp is a first timestamp, the portion is a first portion, the comparison is a first comparison, and the client-time is a first client-time, and wherein the media stream further includes a second watermark encoding a second timestamp of a second portion of the media stream, the operations further comprising:

extracting the second timestamp from the second watermark,

wherein computing the time offset based on the first comparison of the first extracted timestamp with the first client-time according to the clock of the media client comprises computing the time offset based on (i) the first comparison and (ii) a second comparison of the extracted second timestamp with a second client-time according to the clock of the media client.

18. The non-transitory data storage of claim 15 , wherein the content-related action comprises dynamic content modification.

19. The non-transitory data storage of claim 15 , wherein the content-related action comprises dynamic ad replacement.

20. The non-transitory data storage of claim 15 , wherein the operations further comprise:

receiving a directive for the media client to carry out the content-related action in the media stream, the directive specifying an action time point when the media client should carry out the content-related action,

wherein using the computed time offset as a basis to control when the media client will carry out the content-related action in the media stream comprises applying the computed time offset as a basis to translate the specified action time point into an associated client-time point according to the clock of the media client.