Browse Prior Art Database

Stream Scheduler for MPEG-2 Transport Stream Multiplexer

IP.com Disclosure Number: IPCOM000123332D
Original Publication Date: 1998-Sep-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 85K

Publishing Venue

IBM

Related People

Goodridge, S: AUTHOR [+2]

Abstract

Transmission of digitized audio-visual data over a single communications channel requires the multiplexing of two or more real-time data streams into a combined stream for transmission. At the destination, this combined stream is demultiplexed into its component streams for decoding and presentation. The data rates and sizes of the data buffers for each decoder place constraints on the multiplexer behavior at the sending side. If the multiplexer under-services packets from one of the component streams and over-services another, the destination decoder buffers may underflow or overflow. Likewise, buffers on the encoder side may overflow if not serviced by the multiplexer. Underflow and overflow may be minimized with larger buffer sizes, at the cost of added hardware and latency.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Stream Scheduler for MPEG-2 Transport Stream Multiplexer

   Transmission of digitized audio-visual data over a single
communications channel requires the multiplexing of two or more
real-time data streams into a combined stream for transmission.  At
the destination, this combined stream is demultiplexed into its
component streams for decoding and presentation.  The data rates and
sizes of the data buffers for each decoder place constraints on the
multiplexer behavior at the sending side.  If the multiplexer
under-services packets from one of the component streams and
over-services another, the destination decoder buffers may underflow
or overflow.  Likewise, buffers on the encoder side may overflow if
not serviced by the multiplexer.  Underflow and overflow may be
minimized with larger buffer sizes, at the cost of added hardware and
latency.

   The MPEG-2 Systems standard (ISO/IEC 13818-1) defines a
standard Transport Stream System Target Decoder which may be
assumed.  A technique to optimally interleave audio, video, and
system packets for this decoder (with known data rate and buffer
sizes) is described here.  The following criteria are used to decide
which source stream (video, audio, system) should provide the next
packet to the multiplexer: Earliest-Deadline to Underflow
Prioritization: The elementary stream that is closest to reaching an
underflow condition on its decoder buffer receives priority from the
multiplexer.  This scheduling metric is optimal for preventing buffer
underflow since the channel bandwidth utilization must be less than
100 per cent.  Undersized Encoder Buffers: The buffer provided
between each stream (video, audio, system) encoder and the
multiplexer is limited to less than the size of the corresponding
decoder buffers.  Since the encoder buffers fill at the same rate
that the decoder buffers drain, overflow of the decoder buffers is
prevented.  Complementary Buffer Fullness: If, at the start of a
stream, the multiplexer waits until an encoder buffer fills before it
begins sending data for that st...