Method for multiplexing, in MPEG stream processor, packets of several input MPEG streams into one output transport stream with simultaneous correction of time stamps

• US 20040218633A1
• Filed: 04/13/2004
• Published: 11/04/2004
• Est. Priority Date: 04/14/2003
• Status: Abandoned Application

• Current Assignee: Advanced Digital Broadcast (UK) Ltd. (Advanced Digital Broadcast Holdings SA), Advanced Digital Broadcast Polska SPZ OO
• Original Assignee: Advanced Digital Broadcast Polska SPZ OO
• Inventors: Burzynski, Kamil
• Application Number:
  US10/823,029
• Publication Number:
  US 20040218633A1
• Time in Patent Office: Days
• US Class Current: 370/474
• CPC Class Codes: H04N 21/23406 involving management of server-side video buffer
• CPC Class Codes: H04N 21/23608 Remultiplexing multiplex streams, e.g. involving modifying time stamps or remapping the packet identifiers
• CPC Class Codes: H04N 21/44004 involving video buffer management, e.g. video decoder buffer or video display buffer

Abstract

According to the invention, input MPEG data packets are delivered to appropriate stream buffers from asynchronous program sources. The MPEG data packets have different transmission speeds with defined time stamps of their packets, while the packets of input MPEG streams are multiplexed and have their time stamps corrected in such a way that their assigned time stamps are deleted and replaced by values of time markers calculated according to the algorithm detecting and correcting the detected synchronization errors, after which the packets with so corrected time stamps are appended appropriately to the output MPEG stream. The essence of the invention is based in that packets of each input MPEG stream are transferred from stream buffers to appropriate packet buffers together with information about the time ratios between the neighboring packets of a given MPEG input stream. After that, input packets of MPEG streams are retrieved from the mentioned packet buffers by means of a multiplexer to the packet converter. In the packet converter there is a check of the time ratios between the neighboring packets of input streams, the state of the clock of a given output stream, the time of sending the last packet from the given packet buffer and the allowed time offset of packets in the output stream and on their basis the time markers, included in them, are corrected according to the value of the clock of MPEG output stream. Next, selected packets are appended adequately to the MPEG output stream.

Claims

1. A method for multiplexing, in MPEG stream processor, packets of input MPEG streams into one output transport stream with simultaneous correction of time stamps, where input streams of MPEG data are supplied with defined time stamps of their packets and at the same time packets of MPEG input streams are multiplexed and their time stamps are corrected in such a way that their set time stamps are removed and replaced with the values of time stamps calculated according to the algorithm, which detects and corrects the detected synchronization errors and next, packets with so corrected time stamps are appended suitably to the output MPEG stream, characterized in that:

a. packets of every input MPEG stream are transmitted from stream buffers to appropriate packet buffers, together with information about time relations between the neighboring packets of a given input MPEG stream and afterwards,

b. the packets of input MPEG streams are retrieved from the mentioned packet buffers to packet processing unit by means of a multiplexer

i. and in the packet processing unit,

the time relations between the neighboring packets of input streams are checked and

the time relations are also checked for the state of the clock of a given output stream, the time of sending the last packet from a given packet buffer and the allowed time offset of packets in the output stream

and based on them the time stamps contained in them are corrected according to the value of the clock of the output MPEG stream

c. and next appropriately selected packets are appended to the output MPEG stream.

2. The method, according to claim 1, characterized in that the packets supplied to the stream buffers are filtered according to specific criteria.

3. The method, according to claim 2, characterized in that the criteria of filtering packets are specified by the PID numbers of the supplied packets.

4. The method, according to claim 1, characterized in that data are transmitted from stream buffers to packet buffers at the request of the output module.

5. The method, according to claim 1, characterized in that the data from stream buffers are transmitted to the packet buffers after checking that the packet buffer can receive them.

6. The method, according to claim 1, characterized in that in case of equipping the stream buffer with additional clock, the frequency of this clock adjusts to the frequency of the clock of time stamps of packets of a given stream, based on the average value, calculated from at least two measurements of the values of time stamps of packets of a given stream.

7. The method, according to claim 1, characterized in that in the system processing MPEG streams, changes of the quantity of available stream buffers are monitored by means of an independent process and based on these changes packet buffers are added or removed.

8. The method, according to claim 1, characterized in that time relations between the neighboring packets of a given stream are defined as a difference of the time stamps between the current, and the previous packet of a given stream.

9. The method, according to claim 8, characterized in that for the first packet from the given input stream, the time stamp of the previous packet is defined as equal to the-time stamp of the current packet.