US 6,724,825 B1 · Regeneration of program clock reference data for MPEG transport streams

Abstract

A system for providing an accurate time reference for multiple input and output digital video signals of a transcoder that is particularly suited for use with MPEG data. The multiple streams are synchronized with a single master system time clock at the transcoder. Timing data from the master clock is compared to timing data from packets that are input to the transcoder to determine an offset. In particular, timing data, such as a program clock reference (PCR) field, is recovered from packets of different channels that are input to the transcoder. For each channel, timing data is then provided for packets that are output from the transcoder based on the offset and timing data of the master clock at the respective output times. In particular, the adjusted timing data is determined as a sum of the offset and an associated hardware error, less a delay (PcrSysDly) associated with the transcoder, which includes a lookahead delay and a buffer delay. The associated hardware error represents an error of the master clock and/or a system time clock of an encoder that encoded the particular channel.

Claims33

Dependent claims

A method for providing adjusted timing data for a plurality of respective channels that are input to a transcoder, comprising the steps of:

for each channel, recovering timing data (PcrIn) from at least one packet thereof that is input to the transcoder at a respective input time, and determining an associated offset (PcrOffset) between the recovered timing data (PcrIn) and timing data (PcrInHwTag) of a master system time clock of the transcoder at the respective input time;
and
for each channel, providing adjusted timing data (PcrOut) in at least one packet thereof that is output from the transcoder at a respective output time according to the associated offset (PcrOffset), and timing data (PcrOutHwTag) of the master system time clock at the respective output time;
wherein for at least one particular channel, the adjusted timing data (PcrOut) is further provided in the at least one packet that is output from the transcoder according to a hardware error (PcrHwErr) associated with:
(a) the master system time clock, and (b) a system time clock of an encoder that encoded the particular channel.

2 more elements

An apparatus for providing adjusted timing data for a plurality of respective channels that are input to a transcoder, comprising:

means for recovering, for each channel, timing data (PcrIn) from at least one packet thereof that is input to the transcoder at a respective input time, and determining an associated offset (PcrOffset) between the recovered timing data (PcrIn) and timing data (PcrInHwTag) of a master system time clock of the transcoder at the respective input time;
and
means for providing, for each channel, adjusted timing data (PcrOut) in at least one packet thereof that is output from the transcoder at a respective output time according to the associated offset (PcrOffset), and timing data (PcrOutHwTag) of the master system time clock at the respective output time;
wherein for at least one particular channel, the adjusted timing data (PcrOut) is further provided in the at least one packet that is output from the transcoder according to a hardware error (PcrHwErr) associated with:
(a) the master system time clock, and (b) a system time clock of an encoder that encoded the particular channel.

2 more elements

Dependencies are inferred from the claim text.

Regeneration of program clock reference data for MPEG transport streams

Life of this patent

Regeneration of program clock reference data for MPEG transport streams

Life of this patent

Abstract

Claims33