Progressive video refresh slice detection

A method of partially encrypting a digital video signal, comprising:

• examining unencrypted packets of data in the digital video signal to identify at least one specified packet type, the at least one specified packet type comprising packets in a set of N consecutive slices in a frame wherein the a second byte after a slice start code is identical in all N consecutive slices;
• encrypting packets identified as being of the specified packet type using a first encryption method to produce first encrypted packets;
• and
• replacing the unencrypted packets of the specified packet type with the first encrypted packets in the digital video signal to produce a partially encrypted video signal.

A selective encryption encoder, comprising:

• a packet identifier that identifies packets of at least one specified packet type;
• a packet duplicator that duplicates the identified packets to produce first and second sets of the identified packets;
• means for sending and receiving packets to and from a primary encryption encoder to encrypt the first set of identified packets under a first encryption method;
• a secondary encrypter for encrypting the second set of identified packets under a second encryption method;
• and
• wherein the packet identifier identifies packets in a set of N consecutive slices in a frame wherein the a second byte after a slice start code is identical in all N consecutive slices.

A television set-top box, comprising:

• a receiver receiving a digital television signal comprising:
• a plurality of unencrypted packets;
• and
• a plurality of encrypted packets, wherein the encrypted packets are of at least one selected packet type and the at least one specified packet type comprising packets in a set of N consecutive slices in a frame wherein the a second byte after a slice start code is identical in all N consecutive slices;
• a decrypter that decrypts the encrypted packets;
• and
• a decoder that decodes the unencrypted packets and the decrypted packets to produce a signal suitable for play on a television set.

A selective encryption decoder, for decrypting and decoding a selectively encrypted digital video signal, comprising:

• a demultiplexer that receives packets of digital video, certain of the packets being unencrypted and certain of the packets being encrypted, wherein certain of the encrypted packets comprise packets in a set of N consecutive slices in a frame wherein the a second byte after a slice start code is identical in all N consecutive slices;
• the unencrypted packets having a first packet identifier (PID) and the encrypted packets having a second packet identifier (PID);
• a decrypter receiving the encrypted packets having the second PID and decrypting the encrypted packets using a first encryption method to produce decrypted packets;
• a PID remapper that changes at least one of the first and second PIDs so that the unencrypted packets and the decrypted packets have the same PID;
• and
• a decoder that decodes the unencrypted and decrypted packets to produce a decoded video signal.

A method of decrypting and decoding a selectively encrypted digital video signal, comprising:

• receiving packets of digital video, certain of the packets being unencrypted and certain of the packets being encrypted, wherein certain of the encrypted packets comprise packets in a set of N consecutive slices in a frame wherein the a second byte after a slice start code is identical in all N consecutive slices;
• the unencrypted packets having a first packet identifier (PID) and the encrypted packets having a second packet identifier (PID);
• decrypting the encrypted packets having the second PID to produce decrypted packets;
• remapping at least one of the first and second PIDs so that the unencrypted packets and the decrypted packets have the same PID;
• and
• decoding the unencrypted and decrypted packets to produce a decoded video signal.

A computer readable medium that carries instructions that when executed on a programmed processor to facilitate operation of a video receiver device to decrypt and decode a selectively encoded digital video signal wherein the instructions comprise:

• a code segment that controls a demultiplexer that receives packets of digital video, certain of the packets being unencrypted and certain of the packets being encrypted, wherein certain of the encrypted packets comprise packets in a set of N consecutive slices in a frame wherein the a second byte after a slice start code is identical in all N consecutive slices, the unencrypted packets having a first packet identifier (PID) and the encrypted packets having a second packet identifier (PID);
• a code segment that controls decryption of the encrypted packets to produce decrypted packets;
• a code segment that controls remapping at least one of the first and second PIDs so that the unencrypted packets and the decrypted packets have the same PID;
• and
• a code segment that controls decoding the unencrypted and decrypted packets to produce a decoded video signal.

A selectively encrypted digital video signal embodied in a carrier wave, comprising:

• a stream of packets of video data, wherein the stream of packets when not encrypted represent a segment of video content;
• certain of the packets being unencrypted and certain of the packets being encrypted, wherein certain of the encrypted packets comprise packets in a set of N consecutive slices in a frame wherein the a second byte after a slice start code is identical in all N consecutive slices;
• a first segment of code that identifies the unencrypted packets by a first packet identifier (PID);
• and
• a second segment of code that identifies the encrypted packets by a second packet identifier (PID).

A selectively encrypted digital video signal embodied in a computer readable medium, comprising:

• a sequence of packets of video data, wherein the sequence of packets when not encrypted represent a segment of video content;
• wherein certain of the packets are unencrypted;
• wherein certain of the packets have been produced by decrypting encrypted packets;
• wherein certain of the decrypted packets comprise packets in a set of N consecutive slices in a frame wherein the a second byte after a slice start code is identical in all N consecutive slices;
• and
• a segment of code that identifies the unencrypted packets by a first packet identifier (PID);
• and
• a segment of code that identifies the encrypted packets by a second packet identifier (PID).

A method of detecting intra-coded slices in a progressive refresh frame of video data, comprising:

• reading a macroblock byte value in a plurality of adjacent slices of a frame of video data;
• comparing the macroblock byte values in a the plurality of adjacent slices;
• and
• determining that the adjacent slices are intra-coded slices if the macroblock byte values are the same in the plurality of adjacent slices.

A method of detecting intra-coded slices in a progressive refresh frame of video data, comprising:

• reading a second byte following a slice start code in a plurality of adjacent slices of a frame of video data;
• comparing the second byte following the slice start code values in N adjacent slices;
• and
• determining that the N adjacent slices are intra-coded slices if the values are the same in the N adjacent slices.