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Brandwidth optimization of video program bearing transport streams
| Details |
Inventors: Robinett, Robert; Gratacap, Regis;
Assignee: SkyStream Networks Inc. (Sunnyvale, CA)
Primary Examiner: Patel; Ajit
Assistant Examiner: Nguyen; Hanh
Attorney, Agent or Firm:
A method and system are provided for remultiplexing program bearing data. The remultiplexing method and system are applicable to MPEG-2 compliant transport streams carrying video programs. A descriptor based system is used for scheduling the timely output of transport packets wherein each descriptor records a dispatch time as well as a receipt time for each transport packet. The receipt time is used for estimating program clock reference adjustments, but final program clock reference adjustment is performed in hardware in relation to the precise output timing of each transport packets. A descriptor and transport packet caching technique is used for decoupling the synchronous receipt and transmission of transport packets from any asynchronous processing performed thereon. The descriptors can also be used for managing scrambling and descrambling control words (encryption and decryption keys). Remultiplexing functions may be distributed across a network. The remultiplexer can furthermore optimize the bandwidth of transport streams by replacing null transport packets with transport packet data to be inserted into the output transport stream. Program data transmitted via asynchronous communication links is re-timed and assistance is provided for outputting program data on such asynchronous communication links to reduce a variation in end-to-end delay incurred by the program data. Remultiplexing and program specific information can be seamlessly dynamically varied without stopping, or introducing a discontinuity in, the flow of outputted transport packets. A technique is also provided for locking multiple internal reference clock generators. |
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DETAILED DESCRIPTION These and other objects are achieved according to the present invention.
An illustrative application of the invention is the remultiplexing one or more MPEG-2 compliant transport streams (TSs).
TSs are bit streams that contain the data of one or more compressed/encoded audio-video programs.
Each TS is formed as a sequence of fixed length transport packets.
Each compressed program includes data for one or more compressed elementary streams (ESs), such as a digital video signal and/or a digital audio signal.
The transport packets also carry program la clock references (PCRs) for each program, which are time stamps of an encoder system time clock to which the decoding and presentation of the respective program is synchronized.
Each program has a predetermined bit rate and is intended to be decoded at a decoder having a TS buffer and a video decoder buffer of predetermined sizes.
Each program is encoded in a fashion so as to prevent overflow and underflow of these buffers.
Program specific information (PSI) illustratively is also carried in selected transport packets of the TS for assisting in decoding the TS.
According to one embodiment, a remultiplexer node is provided with one or more adaptors, each adaptor including a cache, a data link control circuit connected to the cache and a direct memory access circuit connected to the cache.
The adaptor is a synchronous interface with special features.
The data link control circuit has an input port for receiving transport streams and an output port for transmitting transport streams.
The direct memory access circuit can be connected to an asynchronous communication link with a varying end-to-end communication delay, such as a bus of the remultiplexer node.
Using the asynchronous communication link, the direct memory access circuit can access a memory of the remultiplexer node.
The memory can store one or more queues of descriptor storage locations, such as a queue assigned to an input port and a queue assigned to an output port
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Television 
