Title of Invention

A METHOD, TRANSMITTER AND RECEIVER FOR TRANSMISSION AND RECEPTION END CONDITIONING OF AUDIO DATA

Abstract

Audio data from a useful signal source (1) are split (2) into a main data stream (HD) and an additional data stream (ZD). The main data stream (HD) accommodates at least as much information as is necessary for comprehensible reproduction of at least one useful signal source (1). The main and additional data streams are transmitted in different channels (K1, K2) within a prescribed channel raster.It is possible to increase the reproduction quality of the audio signal within a prescribed channel raster.

Full Text

ROBERT BOSCH GMBH, 70442 Stuttgart Method for conditioning source-coded audio data, and transmitter and receiver for this purpose Prior art The invention is based on a method for the transmission-end or reception-end conditioning of source-coded audio data from at least one useful signal source, in particular for transmission via AM channels in a prescribed channel raster. For transmitting digital audio data, in particular via AM channels in a prescribed channel raster having channels 9 or 10 kHz wide {medium wave in America) , on medium and long wave and also short wave, three different transmission systems have been developed within the DRM (Digital Radio Mondiale) consortium. All of these systems use a conventional AM channel for transmission. With the T2M method, the digital information can be input by auxiliary carrier onto the AF input of the transmitter and can be transmitted in parallel with the AM analogue signal (Funkschau No. 14, 1998, pages 44 to 46). The Skywave 2000 method uses a multicarrier method with TCM {Trellis Code Modulation) modulation in conjunction with QAM (Conference Paper of the 51st Broadcast Engineering Conference, NAB 97, pages 27 to 48, Progress Towards the Development of Digital Modulation in the Longwave, Mediumwave and Shortwave Bands; IBE, Transmission Engineering, March 1999, pages 53 and 54). Advantages of the invention The measures based on the patent claims can be used to attain an increase in a reproduction quality, for example a better tone quality, without the need to move away from the prescribed channel raster, as is necessary in the case of the methods mentioned in the introduction or can be achieved without losses of quality only by using complex coding. In the case of the inventive solution with coupling of a main data stream and at least one additional data stream in different channels in the channel raster, the reception-end useful data rate can be increased and hence a quality improvement can be attained as compared with conventional methods. With the method in accordance with the invention, relatively simple receivers can be used to demodulate and to decode only the main data stream, which results in comprehensible reproduction at a low bit rate of approximately 24 kilobits/s. Receivers with high reproduction quality demodulate and decode both the main data stream and at least one additional data stream of a useful signal and logically combine these two data streams such that a relatively high reproduction quality is obtained. Although DVB signals are also resolved into a base layer and an extension layer, these layers are transmitted in the same channel. In that case, by contrast with the invention, a simple receiver is needed to receive the entire data stream and can only then perform a split. The method based on the invention permits numerous combinations to increase the reproduction quality, for example to reduce the coding artifacts, extend the audio bandwidth or extend the three-dimensional auditory impression, for example a change from mono to stereo. Drawings The drawings are used to explain exemplary embodiments of the invention in more detail. In the drawings. Figure 1 shows the transmission-end and reception-end conditioning of the audio data on the basis of the invention. Figure 2 shows the representation of AM channels within a prescribed channel raster. Figure 3 shows the transmission-end and reception-end conditioning of the audio data on the basis of the invention using a receiver for high-quality reproduction, Figure 4 shows the conditioning of a stereo signal. Figure 5 shows combinations for splitting and combining audio data in a base layer and an extension layer. Description of exemplary embodiments In the case of the inventive implementation shown in Figure 1, by way of example, PCM data from a useful signal source 1 are coded at the transmission end using a source coder 2. in this context, the encoded signal is split into a main data stream HD (base layer) and at least one additional data stream ZD (extension layer), i.e. in this exemplary embodiment the source coder 2 simultaneously acts as a splitting device for the audio data from the useful signal source 1. The main and additional data streams are modulated using the modulation device 3 and are accommodated in respectively different channels, for example the adjacent channels Kl and K2 (shown in Figure 2) in the prescribed channel raster, for example in the AM central channel raster with an interval of 9 kHz. To transfer the main and additional data streams to the different channels Kl and K2, the respective carrier signals for these channels are supplied to the modulation device 3. Naturally, these channels do not need to be adjacent, as shown in Figure 2, but rather may be accommodated at any points in the prescribed channel raster. The channels used for the additional data ZD may, by way of example, be channels becoming free with parallel program broadcasting on account of the relatively long range for digital modulation, or channels which have been created, or which are yet to be created, by band expansion as a result of channels for other services (coastal radio, maritime radio, aeronautical radio) no longer being required, for example expansion of the AM medium wave range in the USA between 1600 and 1660 kHz or of the short wave range in the 31, 25 and 19 meter bands. The data streams transmitted via separate channels are demodulated and decoded at the reception end. In the exemplary embodiment shown in Figure 1, a basic receiver 4 is provided, i.e. a receiver with low reproduction quality which demodulates and decodes only the main data stream HD using the modulator 5 and the source decoder 6. This is possible because, in accordance with the invention, the main data stream accommodates at least as much information from a useful signal source as is necessary for comprehensible reproduction of the useful signal source. By way of example, the main data stream HD accommodates just enough information from the useful signal source for the reproduction quality not to differ from the previous reproduction quality in the AM channels on medium wave, long wave and short wave, i.e. acceptable comprehensibility of speech but losses of quality in music transmissions. In the exemplary embodiment shown in Figure 3, the transmission end performs the same signal conditioning as in the exemplary embodiment shown in Figure 1, but the reception end is provided with a receiver 7 with high reproduction quality, for example CD quality, which demodulates and decodes both the main data stream HD and the associated additional data stream ZD using the demodulation device 8 and the decoding device 9. In a logic device, the main data stream HD and the associated additional data stream ZD are logically combined with one another in order to achieve a quality improvement in the received audio signal. In the exemplary embodiment shown in Figure 3, the source decoding device 9 simultaneously acts as a logic device. For the correct logical combination of mutually associated main and additional data streams, signaling which indicates whether and at what frequency, i.e. in which channel, an additional data stream ZD (extension layer) provided for the same useful signal source (program source) is present is inserted in the main data stream HD (base layer) at the transmission end. Preferably, additional information which indicates which information is contained in the additional data stream ZD and possibly how the main data stream HD can be joined to the associated at least one additional data stream ZD is inserted in the additional data stream. To evaluate the signaling and/or the additional information, an evaluation device 10 is provided which is preferably associated with the demodulation device. This evaluation device 10 controls the logic device or the source decoder 9 on the basis of the evaluated signals so that associated main and additional data streams are logically combined in sync with one another. In a receiver with high reproduction quality, it is naturally also possible optionally to demodulate and decode only the main data stream HD and hence to operate it as a basic receiver. The text below gives examples of the splitting of the audio data from a useful signal source and possible combinations of main data stream (base layer) and additional data stream(s) (extension layer{s)). The channel Kl shown in Figure 2 may contain, by way of example, the complete mono audio signal from a program source (useful signal source) with a low bit rate in the main data stream, and the channel K2 may contain an additional data stream ZD with all the additional data required for a stereo program with a possibly higher bit rate. The split over the two data streams can, in principle, be implemented using the scalability of MPEG 4 . First-generation receivers and simple cheap receivers are intended to demodulate a channel and to decode a monophonic signal. Receivers with higher reproduction quality are provided to demodulate both channels Kl and K2 and to decode a stereophonic signal. This thus represents a useful transistion scenario from the use of one channel to two channels. With the introduction of DRM, receivers can be developed which decode only the base layer. These receivers can also receive the base layer after the second channel with the extension layer is subsequently put into operation. Besides the stereo reproduction, logically combining the main data stream with the at least one additional data stream can achieve a quality improvement in the following directions: the additional data stream reduces the coding artifacts, and the additional data stream extends the audio bandwidth. It is naturally possible to undertake any combinations of these quality improvement measures, including when stereo reproduction is added. Examples of splits between base layer and extension layer for mono/stereo coding arise as follows: To encode a stereo signal, various methods are provided in the MPEG 4 standard. Of these, methods 2 and 3 below are suitable for the inventive method: 1. Coding of the right (R) and of the left (L) channel. 2. MS stereo coding: from the original signal, a sum signal (mid) and a difference signal (side) is formed before it is quantized. This is shown in Figure 3. The mid signal is transmitted in the base layer, and the side signal is transmitted in the extension layer. 3. Intensity stereo; the right and left channels are not transmitted separately from one another. Only one main channel (base layer) and an associated direction signal (extension layer) are transmitted, from which a stereo signal is formed. Examples of the splitting and combination of main data stream and additional data stream(s) to achieve a variable bit rate are shown in Figure 5. In the first channel, for example channel Kl, an encoded signal having a bit rate x is transmitted. In the second channel, for example K2, all the necessary information for achieving a higher bit rate is transmitted. As Figure 5 shows, besides an additional bit rate in the extension layer, combination with stereo signals is also possible. An example of various coder types - CELP coder for the base layer and AAC (Advanced Audio Coding) coder for the extension layer - is also shown in Figure 5. The following, other splits are additionally possible: the base layer contains two audio data streams from various program sources. The extension layer contains the data streams for increasing the useful data of the audio programs, two or more different base layers in different channels contain a respective audio data stream. The extension layer in one channel contains the additional useful data from two or more audio data streams. For the purposes of digital modulation, numerous previously proposed methods are suitable, for example QAM, MPSK or APSK methods. WE CLAIM : 1. A process for send-side preparation of source-coded audio data of at least one wanted signal source (1), particularly for transmission over AM channels of a pre¬ determined channel grid, characterised by the following features: -The source-coded audio data of at least one wanted signal source (1) is separated (2) into a main data stream (HD) and at least one auxiliary data stream (ZD), whereby at least that much information is stored in the main data stream (HD) as is required for a comprehensible reproduction of at least one wanted signal source (1) and information is stored in the auxiliary data stream (ZD) as is required for quality improvement. -Main and auxiliary data streams (HD, ZD) are modulated and stored in different channels (Kl, K2) respectively of the pre- determined channel grid. 2. The process for preparation of audio data at the receiving side, particularly for transmission over AM charmels of a pre-determined channel grid, wherein the audio data is stored in main and auxiliary data streams (HD, ZD), whereby associated main and auxiliary data streams (HD, ZD) respectively originate from at least one wanted signal source (1) and the associated main and auxiliary data streams are respectively stored in different channels (Kl, K2) of the pre- determined channel grid, in the following manner: -Only the main data stream (HD) is de-modulated and de-coded in a receiver (4) with low transmission quality, -In a receiver (7) with high transmission quality it is optional whether only the main data stream (HD) is de-modulated and de-coded or the main data stream (HD) and at least one associated auxiliary data stream (ZD) are de-modulated and de-coded, whereby associated de-modulated and de-coded data streams are linked in such a manner to one another that this results in an enhancernent of the transmission quality for the wanted data source (1) of which there is at least one. 3. The process as claimed in claims 1 or 2 wherein signalling is inserted in the main data stream (HD) at the send side which indicates whether and in which channel a designated auxiliary data stream is available at the same wanted signal source (1). 4. The process as claimed in claims 1 to 3 wherein auxiliary information in particular, contained in an auxiliary data stream (ZD) indicates which information is contained in the auxiliary data stream and, if necessary, how the main data stream (HD) is to be merged at the receiving side with an associated auxiliary data stream (ZD) of which there is at least one. 5. The process as claimed in claims 2 to 4 wherein the linking of associated main data and auxiliary data streams is carried out, taking at least one of the following criteria into consideration: -for reduction of codmg artefacts, -for enhancement of bandwidth for reproduction of audio data, -for generation of a stereo signal. 6. The process as claimed in claims 1 to 5 wherein the scalability of MPEG 4 data streams is drawn upon to separate source- coded audio data of the wanted signal source (1) into the main data stream and into at least one auxiliary data stream (HD, ZD). 7. A transmitter for preparation of source-coded audio data of at least one wanted signal source (1), particularly for transmission over AM channels of a pre-determined channel grid, characterised by the following features: -a device to separate (2) audio data of a wanted signal source (1) into a main data stream (HD) and at least one associated auxiliary data stream (ZD), -a modulating device (3) for modulation of main and auxiliary data streams, whereby carrier signals in particular can be supplied to this modulating device (3) in such a manner that associated main and auxiliary data streams can be transferred on different channels respectively of a pre-determined channel grid. 8. A receiver for receiving side preparation of source-coded audio data, particularly for transmission over AM channels of a pre-determined channel grid, wherein the audio data is stored in main and auxiliary data streams with the following features: -a de-modulation (5.8) and de-coding device (6.9) for at least main data streams (HD), -an evaluator (10) for signalling and, if required, additional information, whereby the signalling indicates in which channel an auxiliary data stream (ZD) associated with a main data stream (HD) is stored and furnishes additional information, if any is provided, which information is contained in the auxiliary data stream (ZD) and how the main data stream (HD) and at least one auxiliary data stream (ZD) are to be merged at the receiving side, -a linking device (8) for associated main and auxiliary data streams that can be controlled by the evaluator (10).

Documents:

in-pct-2002-137-che abstract-duplicate.pdf

in-pct-2002-137-che abstract.jpg

in-pct-2002-137-che abstract.pdf

in-pct-2002-137-che claims-duplicate.pdf

in-pct-2002-137-che claims.pdf

in-pct-2002-137-che correspondence-others.pdf

in-pct-2002-137-che correspondence-po.pdf

in-pct-2002-137-che description (complete)-duplicate.pdf

in-pct-2002-137-che description (complete).pdf

in-pct-2002-137-che drawings.pdf

in-pct-2002-137-che form-1.pdf

in-pct-2002-137-che form-19.pdf

in-pct-2002-137-che form-26.pdf

in-pct-2002-137-che form-3.pdf

in-pct-2002-137-che form-5.pdf

in-pct-2002-137-che pct search report.pdf

in-pct-2002-137-che pct.pdf

in-pct-2002-137-che petition.pdf