Fingerprinting media content using hashing

1. A server device comprising:

a non-transitory memory storing instructions and configured to store:

a database of frame fingerprints ordered sequentially by media item number and frame number for a plurality of media items; and

a hash table containing a plurality of (key, value) pair entries to the database, each entry including a hashed frame fingerprint and one or more index numbers, each index number mapping the hashed frame fingerprint to a corresponding index slot in the database;

a network interface configured to receive an input set of hashed frame fingerprints of an unidentified media item from a client device, the hashed frame fingerprints ordered chronologically by frame number in the input set; and

a processor operatively coupled to the non-transitory memory and the network interface and configured to execute the instructions, the executed instructions causing the processor to perform operations comprising:

identifying a most recent hashed frame fingerprint in the input set of hashed frame fingerprints;

querying the hash table using the most recent hashed frame fingerprint to identify a plurality of index numbers from the (key, value) pair entry of the hash table that matches the most recent hashed frame fingerprint;

for each identified index number, retrieving a corresponding target block of target frame fingerprints from the database, the target frame fingerprints ordered chronologically by frame number and comprising a most recent target frame fingerprint and one or more preceding target frame fingerprints ordered sequentially backwards in time from the most recent target frame fingerprint, the most recent target frame fingerprint having an index slot in the database corresponding to the identified index number;

determining a corresponding rank distance from the input set of hashed frame fingerprints and each of the retrieved target blocks of target frame fingerprints;

retrieving a media item identifier from the database for the target block of target frame fingerprints associated with a shortest rank distance from the input set of hashed frame fingerprints, the retrieved media item identifier identifying the media item associated with the input set of hashed frame fingerprints; and

sending the retrieved media item identifier to the client device via the network interface, the client device in response to receiving the retrieved media item identifier, requesting overlay content from an overlay decision engine for display on a viewer in communication with the client device.

2. The server device of claim 1 , wherein a number of frame fingerprints within each corresponding target block of the target frame fingerprints corresponds to a number of the frame fingerprints in the input set of hashed frame fingerprints.

3. The server device of claim 1 , wherein determining the corresponding rank distance from the input set of hashed frame fingerprints and each of the retrieved target blocks of target frame fingerprints comprises calculating a sum of an absolute difference between ordinal values of respective hashed frame fingerprints of the input set and the target frame fingerprints for each retrieved target block.

4. The server device of claim 1 , wherein the operations further comprise:

when retrieving the media item identifier from the database, retrieving a frame number for the most recent target frame fingerprint from the target block of target frame fingerprints associated with the shortest rank distance; and

when sending the retrieved media item identifier, sending the frame number for the most recent target frame fingerprint to the client device.

5. The server device of claim 1 , wherein the plurality of media items comprise videos or television programs.

6. A method comprising:

storing, by a server device of an automatic content recognition (ACR) system, frame fingerprints of a plurality of media items ordered sequentially by frame number within a database of non-transitory memory of the ACR system;

storing, by the server device, a plurality of (key, value) pair entries within a hash table of the non-transitory memory, each entry including a hashed frame fingerprint and one or more index numbers, each index number mapping the hashed frame fingerprint to a corresponding index slot in the database;

receiving, at the server device, an input set of hashed frame fingerprints of an unidentified media item from a media device in communication with the server device, the hashed frame fingerprints ordered chronologically by frame number in the input set;

identifying, by the server device, a most recent hashed frame fingerprint in the input set of hashed frame fingerprints;

querying, by the server device, the hash table using the most recent hashed frame fingerprint to identify a plurality of index numbers from the (key, value) pair entry of the hash table that matches the most recent hashed frame fingerprint;

for each identified index number, retrieving, by the server device, a corresponding target block of target frame fingerprints from the database, the target frame fingerprints ordered chronologically by frame number and comprising a most recent target frame fingerprint and one or more preceding target frame fingerprints ordered sequentially backwards in time from the most recent target frame fingerprint, the most recent target frame fingerprint having an index slot in the database corresponding to the identified index number;

determining, by the server device, a corresponding rank distance from the input set of hashed frame fingerprints and each of the retrieved target blocks of target frame fingerprints;

retrieving, by the server device, a media item identifier from the database for the target block of target frame fingerprints associated with a shortest rank distance from the input set of hashed frame fingerprints, the retrieved media item identifier identifying the media item associated with the input set of hashed frame fingerprints; and

sending the retrieved media item identifier from the server device to the media device, the media device in response to receiving the retrieved media item identifier, requesting overlay content from an overlay decision engine for display on a viewer in communication with the media device.

7. The method of claim 6 , wherein a number of frame fingerprints within each corresponding target block of the target frame fingerprints corresponds to a number of the frame fingerprints in the input set of hashed frame fingerprints.

8. The method of claim 6 , wherein determining the corresponding rank distance from the input set of hashed frame fingerprints and each of the retrieved target blocks of target frame fingerprints comprises calculating a sum of an absolute difference between ordinal values of respective hashed frame fingerprints of the input set and the target frame fingerprints for each retrieved target block.

9. The method of claim 6 , further comprising:

when retrieving the media item identifier from the database, retrieving, by the server device, a frame number for the most recent target frame fingerprint from the target block of target frame fingerprints associated with the shortest rank distance; and

when sending the retrieved media item identifier, sending the frame number for the most recent target frame fingerprint to the media device.

10. The method of claim 6 , where the media item comprises a video or television program.

11. An automatic content recognition (ACR) system comprising a non-transitory computer-readable medium storing instructions and a processing device configured to execute the instructions, the executed instructions causing the processing device to perform operations comprising:

storing frame fingerprints of a plurality of media items ordered sequentially by frame number within a database of the non-transitory computer-readable medium;

storing a plurality of (key, value) pair entries within a hash table of the non-transitory computer-readable medium, each entry including a hashed frame fingerprint and one or more index numbers, each index number mapping the hashed frame fingerprint to a corresponding index slot in the database;

receiving an input set of hashed frame fingerprints of an unidentified media item from a media device in communication with the processing device, the hashed frame fingerprints ordered chronologically by frame number in the input set;

identifying a most recent hashed frame fingerprint in the input set of hashed frame fingerprints;

querying the hash table using the most recent hashed frame fingerprint to identify a plurality of index numbers from the (key, value) pair entry of the hash table that matches the most recent hashed frame fingerprint;

for each identified index number, retrieving a corresponding target block of target frame fingerprints from the database, the target frame fingerprints ordered chronologically by frame number and comprising a most recent target frame fingerprint and one or more preceding target frame fingerprints ordered sequentially backwards in time from the most recent target frame fingerprint, the most recent target frame fingerprint having an index slot in the database corresponding to the identified index number;

determining a corresponding rank distance from the input set of hashed frame fingerprints and each of the retrieved target blocks of target frame fingerprints;

retrieving a media item identifier from the database for the target block of target frame fingerprints associated with a shortest rank distance from the input set of hashed frame fingerprints, the retrieved media item identifier identifying the media item associated with the input set of hashed frame fingerprints; and

sending the retrieved media item identifier to the media device via the network interface, the media device in response to receiving the retrieved media item identifier, requesting overlay content from an overlay decision engine for display on a viewer in communication with the media device.

12. The non-transitory computer-readable medium of claim 11 , wherein a number of frame fingerprints within each corresponding target block of the target frame fingerprints corresponds to a number of the frame fingerprints in the input set of hashed frame fingerprints.

13. The non-transitory computer-readable medium of claim 11 , wherein determining the corresponding rank distance from the input set of hashed frame fingerprints and each of the retrieved target blocks of target frame fingerprints comprises calculating a sum of an absolute difference between ordinal values of respective hashed frame fingerprints of the input set and the target frame fingerprints for each retrieved target block.

14. The non-transitory computer-readable medium of claim 11 , wherein the operations further comprise:

when retrieving the media item identifier from the database, retrieving a frame number for the most recent target frame fingerprint from the target block of target frame fingerprints associated with the shortest rank distance; and

when sending the retrieved media item identifier, sending the frame number for the most recent target frame fingerprint to the media device.