AVT: Active Video Transcoder System

User’s Manual


Internal Release Version 1.01 (DRAFT) 
Date: April, 2000 
comments/bugreport: perceptmedia@molokia.medianet.kent.edu


 
 

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We are developing the Active Video Transcoder (AVT) system that can perform full range of video transformation on an MPEG-2 video bit-stream system developed at the MEDIANET lab. The AVT can be dynamically installed and activated on network splice-points inside an Active Network. The AVT system can generate a new bit-stream matching the network characteristics and receiver requirement downstream. 

This document accompanies the AVT software. This experimental system transcodes ISO-/IEC 13818-2 stream. It provides brief instructions on how to install and run the Active Video Transcoder (AVT). This is an interim distribution of a system under development and has been tested only on a limited platform, and is intended for internal use only. Active Video Transcoder System is an application level transformer that can trans-code an incoming MPEG-2 bit-stream into another with new application level video specifications, including adjustment of rates. Follow the instructions below for installation, compilation and invocation of the AVT. Also a sample script has been provided for an example trans-coding session.
 

[ Installation and Compilation | Test Run | General Usage]


 
 
 
 
 
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Distribution:

The name of the current distribution is AVT-v1.tar.gz. You need to first download the file. It is a compressed tar file. First Unzip and untar the file using command:

%gunzip AVT-v1.tar.gz

%tar xvfAVT-v1.tar 

This will create a directory AVT under which are all the required files. Change to AVT directory and use make to build the executables. The make file uses the gcc compiler. Type:

% cd AVT 

%make m2tc 

This will create an executable m2tc. All the codes have been tested under both IRIX 6.5 and Linux system Red Hat Linux 6.1. 

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Sample Run:

A simple trans-coding has been included in this distribution to test the system. In this distribution there is a test input video stream named old.m2v and script file named test.  Also there is a sample parameter file named test.par. This file contains the parameters specified for the output stream. You can run the test file typing:

%test

This shell script run the program for you, this script will read the stream file, one by one decode and simultaneously re-encodes the frames according to new transcoding specifications given in AVT spec file. A set of new specifications is already in the sample AVT specification file test.par. It reads from a test input MPEG-2 bit-stream file named old.m2v and generates a new bit-stream named new.m2s

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General Usage:

The name of the AVT MPEG-2 executable is m2tc. It accepts three command line arguments of the following form specifying the AVT paramet file, name of the input and output stream file.
%m2tc [option]  parameter-file output.m2v input.m2v

Currently, there is only one supported option-f. It runs the AVT in verbose mode displaying all the internal information about the progression. 

The AVT parameters for the outgoing bit-stream have to be specified in the parameter.file. Any ASCII text editor can be used to modify the parameters. Below are some rate parameters which can be adjusted: 

It accepts any valid MPEG-2 video bit-stream specified as in ISO-/IEC 13818-2. The output stream file named new.m2v, also in ISO-/IEC 13818-2 format. An MPEG-2 player will be required if you want to play the output file (not included in this distribution). 

bit_rate: specifying the target bitrate. 
frame_rate_code: defines the frame rate. 
d0i,d0p,dob: initial I P B frame virtual buffer fullness. 
intra_dc_prexision: define the quantizaton of the DC value. 
Setting a custom intra quantization matrix and a custom non intra quantization matrix. 

Current AVT requires that the output should have the same number of the frames in the GOP and the same I/P frame distance.


 

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Acknowledgement: The development of this research has been supported by a DARPA research grant. Also the code has been developed based on Barkley MPEG-2 encoder and decoder.