Browse Prior Art Database

Optimized Data Time Stamps for Digital Audio and Video on a Stochastic Network

IP.com Disclosure Number: IPCOM000105750D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

MacInnis, AG: AUTHOR

Abstract

Disclosed is a method for producing time stamps for coded data which indicates transport delay and jitter, thereby facilitating improved performance of decoders of the coded data. The ISO/IEC 11172 International Standard, produced by the working group JTSC1/SC29/WG11 MPEG (Moving Picture Experts Group) has defined a time stamp referred to coded data, called System Clock Reference (SCR), which identifies when coded data should leave an encoder or enter a decoder. Transmission of digital multimedia, such as MPEG, over stochastic networks will incur variable amounts of delay due to latency in the network; this is referred to as jitter.

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Optimized Data Time Stamps for Digital Audio and Video on a Stochastic Network

      Disclosed is a method for producing time stamps for coded data
which indicates transport delay and jitter, thereby facilitating
improved performance of decoders of the coded data.  The ISO/IEC
11172 International Standard, produced by the working group
JTSC1/SC29/WG11 MPEG (Moving Picture Experts Group) has defined a
time stamp referred to coded data, called System Clock Reference
(SCR), which identifies when coded data should leave an encoder or
enter a decoder.  Transmission of digital multimedia, such as MPEG,
over stochastic networks will incur variable amounts of delay due to
latency in the network; this is referred to as jitter.  In order to
accommodate such jitter in the decoder, the decoder needs additional
buffering beyond what would otherwise be needed, as well as a control
mechanism to effectively smooth the received data rate.  This
additional buffering results in increased operational delay.  The
disclosed technique allows a smaller increase in buffering and
simpler control systems in decoders.

     Normally MPEG data is encoded assuming a transport mechanism
that supports the required data rate with no jitter.  SCR time stamps
indicate the time, as a sample of a continuously running counter,
when data are intended to be received by the decoder (i.e., the time
when they leave the encoder) plus, possibly, an arbitrary and
constant delay.  With no jitter, the SCRs received...