Digital Video Watermarking

8/8/2019 Digital Video Watermarking

1/6

HistoryThe roots of watermarking are considered to be in the study of

Steganography. The word comes from the old Greek language and can be

translated as cover writing. Steganography was basically a way of

transmitting hidden (secret) messages between allies, being used as earlyas 1000 B.C. First references to steganography appear in Homers Iliad

and Histories of Herodotus(440 B.C.)

DefinitionGenerally by watermarking one is hiding a message signal into a

host signal, without any perceptual distortion of the host signal. As the

word watermarking suggests, the mark itself is transparent or

unnoticeable for the human perception system. Usually, the host signal is a

digital media, like audio, video or images. As we all know, the Human VisualSystem (HVS), is far from being perfect and for images/video it is possible

to modify the pixel values without the watermark being visible. Providing

that a certain HVS threshold is not exceeded, the modified (watermarked)

image/video will be undistinguishable to the human eye compared with the

original.

Applications of digital watermarking

The main application of digital watermarking is in copyright

protection. The owner of the image/video adds a watermark to his material

before it is distributed. In this way is possible to track illegal copies ofthe copyrighted material.

Possible applications are:

- Broadcast monitoring of video sequences (digital TV)

- DVD protection and access control

- Database retrieval

- Robust identification of digital content

Classification of watermarks

Excluding the obvious case of visible watermarks, we can classify

the watermarks as FRAGILE or ROBUST. The fragile watermark is used

for detecting even the smallest alteration of an image, while the robust one


2/6

is specially designed to withstand a wide range of attacks, which basically

are trying to remove the watermark, but without destroying the

image/video.

Uncompressed data

Bit-stream marking

Invisible

Visible

(Logos, Paper Watermarks)

Robust

Fragile

Types of watermarks

Fingerprints, Labels

Watermarks

A watermark can be added to the uncompressed data (raw data),

such as a standard uncompressed video sequence as described by ITU-R

601, or can be added to the compressed bit-stream (MPEG2).

Non Perceptual

Perceptual VIP Video Independent, Perceptual


3/6

VDP Video Dependent, Perceptual

Type of marking

SPATIAL DOMAIN

FREQUENCY DOMAINDCT

DWT

FFT

The easiest (simplest) way to watermark an image/video, is to

change directly the values of the pixels, in the spatial domain. A more

advanced way to do it, is to insert the watermark in the frequency domain,

using one of the well known transforms: FFT, DCT or DWT. Other

techniques are possible as well, like using fractals for example.

The watermark embedding can be done uniformly (or in some other

empirical manner), which doesnt account for the HVS properties (this is

called non-perceptual marking). Or, the watermarking embedding can use

some HVS models in order to optimise the embedding. Depending on theHVS model used, the perceptual marking can be video independent (basic

HVS model) or preferably video dependent (advanced HVS model).

The Watermarking System


4/6

1. The watermark embedding: the original video is watermarked with a

binary sequence of 64 data-bits, using a secret key, resulting the

watermarked video.

Watermark

Embedding

011011101010

Watermark Data Bits

(min. 64 bits)

Original Frames

Marked Frames

Secret Key

Marking

2. The watermarked video is now in the distribution channel.

Distribution Channel


5/6

Here one could try to attack the watermark, in order to destroy it.

For example, a pirate who wants to breach the intellectual property rights

of the real owner, has all the interest to remove the watermark. In this

case the attacks are intentional. It is important to mention here, that the

intentional attacks must not alter too much the video sequence, because

the attacker still wants to use it, and a bad quality video sequence is

worthless. Some examples of intentional attacks are: the geometricattacks, frame dropping, collusion, etc.

A different class of attacks are those qualified as unintentional,

for example those caused by typical processing in the video chain and

during transmission of the video signal.

3. Finally, the watermarking retrieval, which is the most difficult part of

the system, has to recover the watermark.

Marked Frames

(attacked)Retrieving

011011101010

Watermark Data Bits

Secret Key

Watermark

Retrieving


6/6

Digital Video Watermarking

Documents

Transcript of Digital Video Watermarking