Browse Prior Art Database

Datastream Control in Broadcast Multimedia Networking

IP.com Disclosure Number: IPCOM000114490D
Original Publication Date: 1994-Dec-01
Included in the Prior Art Database: 2005-Mar-28
Document File: 4 page(s) / 98K

Publishing Venue

IBM

Related People

Bellinghausen, JM: AUTHOR [+2]

Abstract

This disclosure addresses the requirement of maintaining a smooth, continuous datastream from a source to a multimedia application in a broadcast environment. With no control flow from the destination application back to the source, the application must be capable of controlling the flow of multimedia information to the user. This disclosure purposes that each destination maintain a smoothing buffer, and that it monitor the level of its buffer and take action to prevent a pending underrun or overrun.

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This is the abbreviated version, containing approximately 52% of the total text.

Datastream Control in Broadcast Multimedia Networking

      This disclosure addresses the requirement of maintaining a
smooth, continuous datastream from a source to a multimedia
application in a broadcast environment.  With no control flow from
the destination application back to the source, the application must
be capable of controlling the flow of multimedia information to the
user.  This disclosure purposes that each destination maintain a
smoothing buffer, and that it monitor the level of its buffer and
take action to prevent a pending underrun or overrun.

      To prevent an underrun condition, a destination should set an
underrun threshold in its buffer, and if the amount of data falls
below this level, the destination should begin to replicate frames
stored in the buffer (Fig. 1).  Each frame could be duplicated,
triplicated, etc. as needed so that the net effect is to raise the
level of the smoothing buffer to within a range that is considered
normal.  This must be done so that the replicated frames are grouped
together so that they are played back contiguously in time.  The user
might see a pause as each replicated frame persists for an integral
multiple of the usual one thirtieth of a second.  This effect is much
less severe and more importantly, is momentary, perhaps
imperceptible, as compared to letting the buffer underrun.  If the
buffer totally underruns, the video will continually breakup with no
chance of recovery.

      To prevent an overrun, as before, the destination sets an
overrun threshold in its smoothing buffer.  If the level rises above
the threshold, the destination starts discarding frames (Fig. 2).
The frames should be discarded in such a way to minimize the
discontinuity to the playback mechanism such as discarding every
other frame or perhaps two frames of every three.  The effect to the
user, if perceptible, will be a jerkiness in the motion.  Again, this
is far better that letting the smoothing buffer overfill, in which
case the jerkiness could remain through the rest of the application.

      In implementing this disclosure, several points should be
considered.  First, at what point sh...