Method and apparatus for modifying the rate of MPEG transport streams
AssigneeJuniper Networks, Inc.
InventorIssac Wingfield
Life of this patent
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Abstract
In a cable modem system, increasing or decreasing the rate of an MPEG Transport Stream involves two separate, but related, tasks: 1) incorporating a sufficient number of additional packets (or discarding packets) to make up for the difference in data rates between input and output, and 2) altering timing information (for instance, PCR (Program Clock Reference) values) present in some incoming packets to reflect their altered positions in the output stream. Both of these tasks can be facilitated by the use of a FIFO (First-In, First-Out) structure, through which the data flows.
Claims20
An automated method, comprising:
- receiving, at a network device, a Moving Pictures Expert Group (MPEG) packet via a transport stream having an associated transport stream rate;
- determining via the network device, that a fill level of a first in first out (FIFO) register is below a threshold value, where the FIFO register is to receive the MPEG packet and where the FIFO register is downstream of the network device;
- and
- in response to the determining that the fill level of the FIFO register is below the threshold value, forwarding, the network device, the MPEG packet to the FIFO register.
An automated method, comprising:
- receiving at a one-packet buffer, a Motion Pictures Expert Group (MPEG) packet;
- identifying, via the one-packet buffer, a watermark value related to a first in first out (FIFO) register, the FIFO register being downstream with respect to the one-packet buffer;
- identifying, via the one-packet buffer, that a number of packets stored in the FIFO register exceeds the watermark value;
- and
- determining whether to drop the MPEG packet from the one-packet buffer in response to identifying that the number of the packets in the FIFO register exceeds the watermark value.
An automated method, comprising:
- determining via a network device, that a Motion Pictures Expert Group (MPEG) packet includes a program clock reference (PCR);
- in response to the determining that the MPEG packet includes the PCR, modifying, via the network device, the MPEG packet, where the modifying includes offsetting the PCR by an offset value;
- and
- forwarding, via the network device, the modified MPEG packet having the offset PCR to a downstream first in first out (FIFO) register.
A hardware register, comprising:
- storage to:
- receive a Motion Pictures Expert Group (MPEG) packet as part of a MPEG transport stream having a transport rate associated therewith,
- receive a stuffing packet prior to receiving the MPEG packet when a quantity of packets stored at the hardware register is below a watermark value,
- store at least one of the MPEG packet or the stuffing packet, and
- send the MPEG packet, the stuffing packet, or one of the quantity of packets to a destination at a quadrature amplitude modulation (QAM) rate, where the QAM rate differs from the transport rate.
Dependencies are inferred from the claim text.