AVT: Active Video Transcoder System
User’s Manual
Internal Release Version 1.01 (DRAFT)
Date: April, 2000
comments/bugreport: perceptmedia@molokia.medianet.kent.edu
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]
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.
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.
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.
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.
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