Abstract: Lossless compression schemes with secure
transmission play a key role in telemedicine applications that helps in
accurate diagnosis and research. Traditional cryptographic algorithms
for data security are not fast enough to process vast amount of data.
Hence a novel Secured lossless compression approach proposed in
this paper is based on reversible integer wavelet transform, EZW
algorithm, new modified runlength coding for character
representation and selective bit scrambling. The use of the lifting
scheme allows generating truly lossless integer-to-integer wavelet
transforms. Images are compressed/decompressed by well-known
EZW algorithm. The proposed modified runlength coding greatly
improves the compression performance and also increases the
security level. This work employs scrambling method which is fast,
simple to implement and it provides security. Lossless compression
ratios and distortion performance of this proposed method are found
to be better than other lossless techniques.
Abstract: We study in this paper the effect of the scene
changing on image sequences coding system using Embedded
Zerotree Wavelet (EZW). The scene changing considered here is the
full motion which may occurs. A special image sequence is generated
where the scene changing occurs randomly. Two scenarios are
considered: In the first scenario, the system must provide the
reconstruction quality as best as possible by the management of the
bit rate (BR) while the scene changing occurs. In the second scenario,
the system must keep the bit rate as constant as possible by the
management of the reconstruction quality. The first scenario may be
motivated by the availability of a large band pass transmission
channel where an increase of the bit rate may be possible to keep the
reconstruction quality up to a given threshold. The second scenario
may be concerned by the narrow band pass transmission channel
where an increase of the bit rate is not possible. In this last case,
applications for which the reconstruction quality is not a constraint
may be considered. The simulations are performed with five scales
wavelet decomposition using the 9/7-tap filter bank biorthogonal
wavelet. The entropy coding is performed using a specific defined
binary code book and EZW algorithm. Experimental results are
presented and compared to LEAD H263 EVAL. It is shown that if
the reconstruction quality is the constraint, the system increases the
bit rate to obtain the required quality. In the case where the bit rate
must be constant, the system is unable to provide the required quality
if the scene change occurs; however, the system is able to improve
the quality while the scene changing disappears.