Recording and playback of audio-video transport streams

• US 6,169,843 B1
• Filed: 09/19/1997
• Issued: 01/02/2001
• Est. Priority Date: 12/01/1995
• Status: Expired due to Term

• Current Assignee: Harmonic Incorporated
• Original Assignee: Harmonic Incorporated
• Inventors: Johnson, Brian, Magee, Mark, Lenihan, Michael P., Hart, Sean C.
• Primary Examiner(s): Garber, Wendy
• Assistant Examiner(s): MOE, AUNG SOE
• Application Number:
  US08/933,582
• Time in Patent Office: 1,201 Days
• Field of Search: 386/1, 386/46, 386/111, 386/125, 386/126, 386/95, 370/352, 370/353, 370/357, 370/36, 370/394, 370/395, 348/423
• US Class Current: 386/201
• CPC Class Codes: H04N 21/235 Processing of additional data, e.g. scrambling of additional data or processing content descriptors
• CPC Class Codes: H04N 21/2368 Multiplexing of audio and video streams
• CPC Class Codes: H04N 21/4113 PC
• CPC Class Codes: H04N 21/4135 external recorder interface circuits between an apparatus for recording television signals and a television receiver H04N5/775
• CPC Class Codes: H04N 21/4305 Synchronising client clock from received content stream, e.g. locking decoder clock with encoder clock, extraction of the PCR packets arrangements for synchronising receiver with transmitter by comparing receiver clock with transmitter clock H04L7/0012; arrangements for synchronising receiver with transmitter wherein the receiver takes measures against momentary loss of synchronisation H04L7/0083
• CPC Class Codes: H04N 21/4334 Recording operations recording of a television signal H04N5/76; arrangements for recording or accumulating broadcast information or broadcast-related information H04H60/27
• CPC Class Codes: H04N 21/434 Disassembling of a multiplex stream, e.g. demultiplexing audio and video streams, extraction of additional data from a video stream; Remultiplexing of multiplex streams; Extraction or processing of SI; Disassembling of packetised elementary stream demultiplexing of data packets for data networks, e.g. RTP/UDP H04L65/00
• CPC Class Codes: H04N 21/4341 Demultiplexing of audio and video streams
• CPC Class Codes: H04N 21/4344 Remultiplexing of multiplex streams, e.g. by modifying time stamps or remapping the packet identifiers
• CPC Class Codes: H04N 21/435 Processing of additional data, e.g. decrypting of additional data, reconstructing software from modules extracted from the transport stream
• CPC Class Codes: H04N 21/8455 involving pointers to the content, e.g. pointers to the I-frames of the video stream
• CPC Class Codes: H04N 9/8042 involving data reduction
• CPC Class Codes: H04N 9/8063 using time division multiplex of the PCM audio and PCM video signals

Abstract

A method and apparatus for recording and playback of transport stream packets including multiplexed audio, video and other data streams. The transport streams may be generated in accordance with an MPEG-2 standard. In a record mode, an arrival timestamp is generated for each input transport packet to be recorded in a peripheral storage device. A given arrival timestamp indicates the arrival time of the corresponding transport packet in the recording system. Each of the transport packets are then stored with their corresponding arrival timestamps. The record mode may utilize a packet identifier (PID) decoder to perform packet filtering such that only incoming transport packets with selected PIDs are stored. In a playback mode, transport packets and corresponding arrival timestamps are retrieved from the storage device and the arrival timestamps are utilized to direct synchronous delivery of the transport packets to, for example, a decoder or a transport stream broadcast system. The playback mode may detect a timestamp discontinuity code in one or more of the arrival timestamps, and adjust the playback system time clock accordingly. The playback mode may also provide null packet interleaving in which a selectable number of null packets are inserted between each valid transport packet to thereby provide a selectable fixed-rate transport packet output. The recording and playback features may be implemented using a spooler card and a storage controller card incorporated into an otherwise conventional personal computer.

Claims

1. A method of playing back transport packets in a transport stream playback system comprising the steps of:

retrieving from storage each of a plurality of formatted packets, including a transport packet with synchronization word, a corresponding formatted arrival timestamp, the arrival timestamp indicative of an arrival time of the corresponding transport packet in a recording system used to store the formatted packets;

distinguishing between said arrival timestamps and said synchronization words based on a bit pattern format of said arrival timestamps which is unambiguously free of any bit pattern that matches said synchronization pattern;

determining if one of the plurality of packets includes a timestamp discontinuity;

altering a playback system time clock in accordance with an identified timestamp discontinuity; and

delivering the transport packets in one or more transport streams in accordance with the corresponding arrival timestamps relative to an independent playback system time clock, wherein the independent playback system time clock is loaded with the arrival time stamp of the transport packet with a playback discontinuity.

2. The method of claim 1 wherein the step of determining if one of the plurality of packets includes a timestamp discontinuity further includes the step of identifying a predetermined code placed in the arrival timestamp of the corresponding packet.

3. The method of claim 1 wherein the step of altering a playback system time clock in accordance with an identified timestamp discontinuity further includes the step of resetting the playback system time clock to a value corresponding to an arrival timestamp of the packet for which the discontinuity was identified.

4. The method of claim 1 wherein the step of altering a playback system time clock in accordance with an identified timestamp discontinuity further includes the step of resetting the playback system time clock to a value corresponding to an arrival timestamp of a packet arriving in the playback system subsequent to the packet for which the discontinuity was identified.

5. The method of claim 1 wherein the step of delivering transport packets further includes the additional step of delivering a predetermined number of null packets between delivery of each of the transport packets retrieved from storage.

6. An apparatus for use in playing back transport packets in a transport stream playback system, the apparatus comprising:

a controller for retrieving each of a plurality of formatted packets, including a transport packet having a synchronization word, and corresponding formatted arrival timestamps from a system storage device, each arrival timestamp indicative of an arrival time of the corresponding transport packet in a recording system used to store that formatted packet, for distinguishing between said arrival timestamps and said synchronization words based on a bit pattern format of said arrival timestamps which is unambiguously free of any bit pattern that matches said synchronization pattern, for determining if one of the plurality of packets includes a timestamp discontinuity, and for altering a playback system time clock in accordance with an identified timestamp discontinuity; and

a spooler operative to deliver the retrieved transport packets in one or more transport streams in accordance with the retrieved arrival timestamps relative to an independent playback system time clock, wherein the independent playback system time clock is loaded with the arrival time stamp of the transport packet with a playback discontinuity.

7. The apparatus of claim 6 wherein the controller determines if one of the plurality of packets includes a timestamp discontinuity by identifying a predetermined code placed in the arrival timestamp of the corresponding packet.

8. The apparatus of claim 6 wherein the controller alters the playback system time clock by resetting the playback system time clock to a value corresponding to an arrival timestamp of the packet for which the discontinuity was identified.

9. The apparatus of claim 6 wherein the controller alters the playback system time clock by resetting the playback system time clock to a value corresponding to an arrival timestamp of a packet arriving in the playback system subsequent to the packet for which the discontinuity was identified.

10. The apparatus of claim 6 wherein the spooler delivers a predetermined number of null packets between delivery of each of the transport packets retrieved from storage.

11. A method of playing back transport packets in a transport stream playback system comprising the steps of:

retrieving from storage each of a plurality of formatted packets, including a transport packet and a corresponding formatted arrival timestamp, the arrival timestamp indicative of an arrival time of the corresponding transport packet in a recording system used to store the formatted packets,

for each formatted packet, determining that the formatted packets includes a timestamp discontinuity if a predetermined portion of the formatted packet other than the transport packet itself equals a particular, fixed, predetermined value, the determination being made for each of plural, sequentially retrieved, formatted packets using the same particular, fixed predetermined value,

altering playback of each transport packets in the formatted packets determined to include a timestamp discontinuity, and

delivering the transport packets in accordance with the corresponding arrival timestamp relative to an independent playback system time clock and in accordance with alterations in playback made for transport packets determined to include the timestamp discontinuity, wherein the independent playback system time clock is loaded with the arrival time stamp of the transport packet with a playback discontinuity.

12. The method of claim 11 wherein transport packets determined to have the timestamp discontinuity are discarded.

13. The method of claim 11 wherein each arrival time stamp contained in each formatted packet is formatted into a pattern of bits that is ambiguously free of a bit pattern that matches a synchronization word of the corresponding transport packet of the formatted packet.

14. A apparatus for use in playing back transport packets in a transport stream playback system, the apparatus comprising:

a controller configured for retrieving from storage each of a plurality of formatted packets, including a transport packet and a corresponding formatted arrival timestamp, the arrival timestamp indicative of an arrival time of the corresponding transport packet in a recording system used to store the formatted packets, for each formatted packet, determining that the formatted packets includes a timestamp discontinuity if a predetermined portion of the formatted packet other than the transport packet itself equals a particular, fixed, predetermined value, the determination being made for each of plural, sequentially retrieved formatted packets using the same particular, fixed predetermined value, and for altering playback of each transport packets in the formatted packets determined to include a timestamp discontinuity, and

a spooler configured for delivering the transport packets in accordance with the corresponding arrival timestamp relative to an independent playback system time clock and in accordance with alterations in playback made for transport packets determined to include the timestamp discontinuity, wherein the independent playback system time clock is loaded with the arrival time stamp of the transport packet with a playback discontinuity.

15. The apparatus of claim 14 wherein transport packets determined to have the timestamp discontinuity are discarded.

16. The apparatus of claim 14 wherein each arrival time stamp contained in each formatted packet is formatted into a pattern of bits that is ambiguously free of a bit pattern that matches a synchronization word of the corresponding transport packet of the formatted packet.