Browse Prior Art Database

METHOD FOR ALLOCATING BUFFER SIZE FOR NON REAL TIME IMAGE TRANSFER

IP.com Disclosure Number: IPCOM000009732D
Original Publication Date: 2000-Jan-01
Included in the Prior Art Database: 2002-Sep-13
Document File: 5 page(s) / 253K

Publishing Venue

Motorola

Related People

Paola Hobson: AUTHOR [+3]

Abstract

This paper describes a system which allows high quality or even lossless images to be obtained from a system that transmits highly compressed video. The enhancement data needed to obtain a higher quality image is buffered, and this data will be trans- mitted in non-real-time. One application may be where a police user wishes to send real-time images from an incident which are of too low quality to be used as evidence in court.

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6% MOTOROLA Technical Developments

METHOD FOR ALLOCATING BUFFER SIZE FOR NON REAL TIME IMAGE TRANSFER

by Paola Hobson, Timor Kadir and David Bourne

ABSTRACT

  This paper describes a system which allows high quality or even lossless images to be obtained from a system that transmits highly compressed video. The enhancement data needed to obtain a higher quality image is buffered, and this data will be trans- mitted in non-real-time. One application may be where a police user wishes to send real-time images from an incident which are of too low quality to be used as evidence in court.

INTRODUCTION

  This paper deals with improvements in the area of very low bit rate video communication e.g. as might be implemented as H.263 encoding over a low bandwidth wireless channel.

  In order to achieve video transmission over very low bandwidth communication channels, a number of techniques may be used: reduction of image reso- lution; reduction of video frame-rate; use of lossy/lossless compression algorithms. Often a combination of the three methods is used to achieve the desired quality/data rate trade-off. The accept- ability of the resulting video quality is determined by the specific application.

PROBLEMS TO BE SOLVED

  For certain applications such as video confer- encing a quite 'low' image quality can be tolerated as long as the update rate is around 7-10 frames per second. However, the same system could not be used to capture images to be used as evidence or identification by the police. The problem is there- fore to allow high quality or even lossless images to be obtained from a system that transmits highly compressed video.

  The capability to view video and then to capture a still image from the video stream is widely used in devices such as digital 'stills' cameras. However, this does not operate over a very low bandwidth link and the video source and storage are both local to the capture end of the system. Video communica- tion systems offering video conferencing features often allow the user to grab a frame from the video stream. However, this image is of the same quality as that originally displayed in the video sequence.

  Round trip delay measurements are often used in communication protocols to set up parameters to ensure optimal throughput. TCP uses a round trip delay measure to set the size of its retransmission window and buffer. In the case of the TCP protocol the measurement of round trip delay is used in order to find some optimum value for the retransmission window and buffer. In the invention, if the frame buffer is set too small the still image request func- tionality would not operate at all.

  In video conferencing end-to-end delay is used for synchronization between audio and video.

  Some video surveillance systems do allow the user to request areas of the video scene to be sent at a higher quality. However, this scheme only trans- mits subsequent frames in higher quality, and does not allow the user to request particular fra...