Method and system for re-multiplexing of content-modified MPEG-2 transport streams using PCR interpolation

• US 20050039064A1
• Filed: 08/13/2003
• Published: 02/17/2005
• Est. Priority Date: 08/13/2003
• Status: Active Grant

• Current Assignee: MK Systems USA Inc.
• Original Assignee: Ericsson Television Incorporated (Telefonaktiebolaget LM Ericsson)
• Inventors: Malhotra, Hemant, Balakrishnan, Jeyendran
• Granted Patent: US 7,693,222 B2
• Time in Patent Office: Days
• US Class Current: 713/400
• CPC Class Codes: H04N 21/23608 Remultiplexing multiplex streams, e.g. involving modifying time stamps or remapping the packet identifiers
• CPC Class Codes: H04N 21/242 Synchronization processes, e.g. processing of PCR [Program Clock References] arrangements for synchronising broadcast or distribution via plural systems in broadcast distribution systems H04H20/18

Abstract

A system and method is provided for revising the time stamp information in an MPEG-2 transport stream after content in the transport stream is modified. According to one method, successive PCR time stamps previously added to the transport stream are used to determine PCR_SYNC time stamps for synchronization points in the transport stream by interpolation. The PCR_SYNC time stamps are substituted into transport packets within the transport stream. The PCR_SYNC is also used to determine modified time of arrival (TOA) stamps to be added to transport packets. According to a second method, PCR interpolation is used to determine the values of PCR_SYNC. TOA interpolation of TOA stamps previously added to the transport stream are used to determine modified TOA stamps to be substituted into the transport stream for the previously added TOA stamps.

Claims

1. A method of processing a series of original elementary stream segments within an original systems stream to produce a modified systems stream, the original elementary stream segments to be processed belonging to at least one elementary stream, the method comprising the steps of:

(a) receiving an original systems stream comprising a series of systems stream segments, each systems stream segment comprising a systems layer specific segment of information and, for system stream segments that are to carry elementary stream data, further comprising one elementary stream segment of a series of original elementary stream segments to be processed, a plurality of the system layer specific segments comprising a first series of program clock reference times;

(b) identifying a plurality of synchronization points within the series of original elementary stream segments in an elementary stream to be processed, wherein the synchronization points are a type of sequential location of the elementary stream (1) which recurs continually throughout the elementary stream, (2) is synchronized in time to a system time clock of the elementary stream, and (3) is present in the elementary stream both prior to and after the processing, the synchronization points including first and second synchronization points that are separated by a particular sequence of information in the elementary stream;

(c) calculating a second series of program clock reference times for the plurality of synchronization points;

(d) processing elementary stream information within the series of original elementary stream segments to produce a modified sequence of elementary stream information to be carried between the plurality of synchronization points, said modified sequence of elementary stream information having a different amount of information than the particular sequence of information; and

(e) inserting the modified sequence of elementary stream information into a series of new system stream segments that include the calculated second series of program clock reference times for the plurality of synchronization points.

2. The method of claim 1, wherein each of the synchronization points is located between two successive program clock reference times of the first series of program clock reference times, and wherein the second series of program clock reference times are calculated according to an equation as follows:

PCR_SYNC=PCR₁+(PCR₂−

PCR₁)*BC_SYNC/(B_PCR2−

B_PCR1),

wherein PCR₁ and PCR₂ are values of the two successive program clock reference times in the first series of program clock reference times for a particular synchronization point of the synchronization points, wherein B_PCR1 and B_PCR2 represent a location by byte in the original systems stream of the values PCR₁ and PCR₂, respectively, counting from a first byte of the original systems stream, and wherein BC_SYNC represents a location by byte of the particular synchronization point relative to B_PCR1.

3. The method of claim 1, further comprising:

(f) upon receipt of each of said systems stream segments, recording an original arrival time and a segment count of each systems stream segment of the original systems stream;

(g) calculating a new arrival time for each of the new system stream segments based on the calculated second series of program clock reference times; and

(h) inserting said calculated new arrival time for each of the system stream segments into a corresponding one of said new system stream segments.

4. The method of claim 3, wherein the step of calculating said new arrival time for each elementary stream segment comprises calculating said new arrival time for each of the system stream segments having one of the first and second synchronization points as a function of at least some of the second series of calculated program clock reference times, and calculating said new arrival time for each of the system stream segments between said system stream segment including the first and second synchronization points based on said new arrival times calculated for the system stream segments having one of the first and second synchronization points.

5. The method of claim 1, further comprising:

buffering system stream segments comprising any of said elementary stream information that is not to be processed while said processing step is performed on other of said elementary stream information, and

re-multiplexing processed and unprocessed system stream segments in accordance with said original arrival times for unmodified system stream segments and in accordance with said newly-calculated arrival times for said new system stream segments.

6. The method of claim 1, wherein each of said system stream segments in the original systems stream has an identifier, wherein said systems stream segments comprises said elementary system segments belonging to a particular elementary stream being identified by the same identifier, and wherein said first series of program clock references are included in a PCR systems stream segment not comprising one of said elementary stream segments and identified by an identifier unique to said PCR system stream segments, said method further comprising:

changing said unique identifier for said PCR system stream segments to one of said identifiers for one of said elementary streams to be processed; and

forwarding said PCR system stream segments for processing with said one of said elementary streams.

7. A method of processing a series of original elementary stream segments within an original systems stream to produce a modified systems stream, the original elementary stream segments to be processed belonging to at least one elementary stream, the method comprising the steps of:

(a) receiving an original systems stream comprising a series of systems stream segments, each systems stream segment comprising a systems layer specific segment of information and, for system stream segments that are to carry elementary stream data, further comprising one elementary stream segment of a series of original elementary stream segments to be processed, a plurality of the system layer specific segments comprising a first series of program clock reference times;

(b) recording an arrival time and a segment count of each systems stream segment of the original systems stream;

(c) identifying a plurality of synchronization points within the series of original elementary stream segments in an elementary stream to be processed, wherein the synchronization points are a type of sequential location of the elementary stream (1) which recurs continually throughout the elementary stream, (2) is synchronized in time to a systems time clock of the elementary stream, and (3) is present in the elementary stream both prior to and after the processing, the synchronization points including first and second synchronization points that are separated by a particular sequence of information in the elementary stream;

(d) calculating a second series of program clock reference times for the plurality of synchronization points;

(e) processing elementary stream information within the series of original elementary stream segments to produce a modified sequence of elementary stream information to be carried between the plurality of synchronization points, said modified sequence of elementary stream information having a different amount of information than the particular sequence of information;

(f) inserting the modified sequence of elementary stream information into a series of new system stream segments that include the calculated second series of program clock reference times for the plurality of synchronization points;

(g) calculating a new arrival time for each of the system stream segments in the new system stream segments based on arrival times and segment counts of each systems stream segment; and

(h) inserting said calculated new arrival time for each of the system stream segments into a corresponding one of said system stream segments.

8. The method of claim 7, wherein each of said system stream segments in the original systems stream has an identifier, wherein said systems stream segments comprises said elementary system segments belonging to a particular elementary stream being identified by the same identifier, and wherein said first series of program clock references are included in a PCR systems stream segment not comprising one of said elementary stream segments and identified by an identifier unique to said PCR system stream segments, said method further comprising:

changing said unique identifier for said PCR system stream segments to one of said identifiers for one of said elementary streams to be processed; and

forwarding said PCR system stream segments for processing with said one of said elementary streams.

9. The method of claim 7, wherein the series of original elementary stream segments contains an intervening segment with no synchronization point between the first and second synchronization points.

10. The method of claim 7, wherein the new series of elementary stream segments comprises an elementary stream segment containing the first synchronization point, an intervening elementary stream segment with no synchronization point, and an elementary stream segment containing the subsequent synchronization point, wherein interpolation is used to calculate an arrival time for the intervening elementary stream segment with no synchronization point.

11. The method of claim 7, wherein the arrival time for the first synchronization point is calculated based on the arrival time of the segment containing the first synchronization point and the position of the synchronization point within the segment containing the synchronization point relative to the start of the segment.

12. The method of claim 7, wherein the calculation of a new arrival time for each elementary stream segment within the series of new elementary stream segments is further based on the ratio of the number of bits in a plurality of original elementary stream segments to the number of bits in a plurality of new elementary stream segments.