AUDIO PERIPHERAL DEVICE

Abstract: An audio peripheral device comprising a USB interface is used to couple for example a computer with loudspeakers. An existing problem of known audio peripheral devices is that it is difficult to mix a stereo PCM stream with an encoded (audio) signal as received from the USB bus. The invention provides a solution for this problem by adding a sample rate converter before mixing the different signals.

Description: Audio peripheral device The invention relates to an audio peripheral device comprising an USB interface. The invention further relates to a method for supplying a digital audio signal. USB (universal serial bus) has been developed by the PC industry for interfacing I/O peripherals to a main system for example a personal computer with loudspeakers. For further information on the USB standard, see Universal Serial Bus, version xx, published by Intel Corporation, Santa Clara, California, USA. Such audio peripheral devices are known in the art. A disadvantage of the known audio peripheral devices is that it is difficult to mix a stereo PCM stream with an encoded (audio) signal as received from the USB bus. It is inter alia an object of the invention is to overcome the disadvantages of the prior art. To this end a first aspect of the invention provides an USB audio peripheral device as claimed in claim 1. A second aspect of the invention provides a method for supplying a digital audio signal as claimed in claim. In order to be able to mix this information digitally, a sample rate converter is necessary. Both streams are not synchronized. The sample rate converter makes it possible to synchronize the PCM stream to the encoded audio stream. In this way it is possible to combine a stereo PCM signal with an encoded signal such as AC3, MPEG2 et al. Embodiments of a device according to the invention are described in the dependent claims. The invention and additional features, which may be optionally, be used to implement the invention to advantage, will be apparent from and elucidated with references to the examples described below hereinafter and shown in the figure. Herein shows: The figure a block schematic example of an USB audio peripheral device, In the figure a block schematic example of an USB audio peripheral device D according to the invention is shown. An input I is coupled to an USB bus USB for receiving a signal from the bus. The input I is coupled to an USB interface l.The USB interface supplies in this example two signals, that is a first signal SI being a stereo PCM stream and a second signal S2 being an encoded audio stream. The signal SI is supplied to a sample rate converter 3 for amending the sample rate of this signal into a signal SI', to synchronize this signal with signal S2. The signal S2 is supplied to a decoder 5 for decoding the encoded audio stream into a signal S2'. The converted signal SI' and the decoded signal S2' are supplied to inputs of a mixer 7 for mixing these signals into an output signal So to be supplied at an output O. the output can be coupled to loudspeakers for example. It is to be noticed that above an audio peripheral device according to the invention has been described on the basis of an example. The man skilled in the art will be well aware of a lot of variations, which fall within the scope of the invention.

Claims: CLAIMS: 1. Audio peripheral device comprising an USB interface for receiving a signal from a USB bus and for supplying a first signal being a PCM stream signal and a second signal being an encoded signal, decoding means for decoding the encoded signal, sample rate conversion means for converting the sample rate of the PCM stream signal and mixing means for mixing the decoded signal and the converted PCM stream signal, and output means for supplying a digital audio output signal. 2. Audio peripheral device according to claim 1, characterized in that the received signal from the USB bus also comprises control parameters for controlling the mixing of the decoded signal and the converted PCM stream signal. 3. Audio peripheral device according to claim 1, characterized in that the mixing means are digital mixing means. 4. Method for supplying a digital audio signal receiving a signal from a USB bus, comprising a first signal being a PCM stream signal and a second signal being an encoded signal, decoding the encoded signal, converting the PCM stream signal and mixing the decoded signal and the converted PCM stream signal and supplying the digital audio signal.

Inventors: DAEMS FRANK C H, VANSPRINGEL WIM J A, DAEMS, FRANK, C., H., VANSPRINGEL, WIM, J., A.
Applicants: KONINKL PHILIPS ELECTRONICS NV, KONINKLIJKE PHILIPS ELECTRONICS N.V.
Application year: 2000
Main classification: H04R3
IPC codes: G06F3, G06F13, G10L19, H04H1