Watermark Embedding for Audio Signals
MusicTrace also offers watermark solutions in addition to broadcast monitoring. This includes the product family ContentMark that permits embedding a digital watermark in audio signals. Depending on the product, this can involve either uncompressed or compressed audio signals.
With the aid of the software products of the ContentMark product family, it is possible to embed additional information into audio signals. This additional information is transmitted to the final user hidden in the music in a form that is imperceptible to human hearing. A further characteristic is the fact that embedding of a watermark does not change the format. The final user does not have to purchase special player devices, instead he can still play these titles using conventional equipment.
The additional data are robustly embedded in the audio signal; this means that they cannot be removed by simple means. The objective of developing the audio watermark technique was to ensure that the watermark does not become unusable until intentional or inadvertent disturbances have degraded the audio quality to such an extent that the recorded title no longer has any economic value.
The information to be embedded is transferred in so-called data containers. Several data containers have already been developed, they differ in the volume of data that is to be transferred, the data rate and the robustness of the watermark. The two most commonly used data containers transfer 48 bits in 5 or 2.7 seconds. Other data containers can be generated as agreed with the customer.
MusicTrace offers various products for different fields of application that are nevertheless mutually compatible. This means that there is only one program for reading out the embedded information, regardless of which product was used to embed this information. The program for reading out watermarks is always a component of the respective ContentMark product. An overview of the available products and their fields of application are given in the following.
ContentMarkPCM permits embedding of watermarks in uncompressed audio signals. These can either be PCM files or WAVE files. The result of processing is still uncompressed audio files that are provided with watermarks.
Typically, ContentMarkPCM is used for embedding copyright information during production. Another possibility is embedding recipient data during the licensing phase of Realtone ringtones, this makes it possible to detect the fraudulent use of titles offered for licensing at a later time.
Currently, mono or stereo signals with sampling frequencies of 32, 44.1, and 48kHz can be processed. ContentMarkPCM is available either as a C++ software library or as an executable command line program and can therefore be integrated into existing production sequences in a correspondingly rapid and simple manner. ContentMarkPCM is available for Windows (Windows 98 and later versions) and Linux operating systems; a Mac OS-X version can be obtained on request.
ContentMarkCD is a specialized form of the product ContentMarkPCM. With the aid of ContentMarkCD it is possible to make any desired number of copies of an audio CD, each bearing a different watermark. These audio CDs sound identical to the human ear, however are discernable on the basis of the watermark. In addition, the program supports printing of CD labels, including information on the respective recipient. The recipient of an audio CD made with ContentMarkCD is thus aware that the audio CD in question was made especially for him.
The preferred field of application of ContentMarkCD is distribution of prerelease recordings of new music to music journalists, for example. Because prerelease distribution typically occurs a few weeks before the official release of a new CD, protection measures are particularly important here to prevent financial loss incurred by the premature appearance of a music track on a music-swap site. At the same time, audio CDs that conform to standards is of particular importance during prerelease distribution to ensure the greatest possible of freedom when listening to music. In this context, watermark technology offers an optimum compromise between security and user-friendliness.
ContentMarkCD is Windows software and currently only runs in conjunction with CD/DVD recording solutions manufactured by Rimage. This software supports making a master DDP image (Version 1.0) of a master CD and generation of audio CDs from a master DDP image or a master CD. The label can be customized using the CD designer available from Rimage; one noteworthy aspect here is the fact that the locations at which information on the recipient are shown can be freely selected when creating labels. The recipients are selected from a list that is generated from a text file. This application software can be run directly on the computer which the Rimage CD recorder is connected to. It can also be run on another computer in the network on which the Rimage client software is installed.
ContentMarkMP3 is a product for embedding watermarks in existing MP3 audio files. The format is not changed by the watermark, consequently the MP3 audio file still conforms with standards. After watermarking, the file can be played on any MP3 player and is accepted by any MP3 player software that also accepts the original MP3 file.
Distributors that operate on the Internet can use ContentMarkMP3 to embed transaction data in the music titles or audio books sold on this platform. This can either be a sequential transaction number or a customer number assigned to the purchaser. Using this information, it is possible to determine at a later time which customer placed a purchased copy of a title on music-swap sites, thereby violating certain usage rights.
ContentMarkMP3 is available either as an executable command line program or as a C++ software library and can be integrated into existing production sequences in a correspondingly rapid and simple manner. ContentMarkMP3 is available for Windows (Windows 98 and later versions) and Linux operating systems; a Mac OS-X version can be obtained on request.
Support for Other Formats
Future plans call for processing of files in other audio formats using the ContentMark product family. ContentMarkAAC for embedding watermarks in AAC audio files - the successor format for MP3 files - is currently under development. Products for the two highly-efficient encoding variants mp3PRO and HE AAC or aacPlus as well as MP3 Surround are to follow soon. A version for embedding watermarks in compressed audio flies created using FLAC lossless compression technology is in preparation.
Furthermore, another special version of the product ContentMarkPCM is planned. With the help of this software and a professional CD recorder, music distributors will be capable of producing audio CDs for their customers that have individually-selected tracks. In other words, these customers can visit an on-line shop or a conventional music store and select from those tracks offered to create their own combinations of tracks that can be ready for delivery or pick-up at the checkout counter in only a short time.
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