Process and device for mixing digital audio signals

Details Process and device for mixing digital audio signals Process and device for mixing digital audio signals

1998-02-05

2001-12-11

Mei, Xu (Department: 2644)

Electrical audio signal processing systems and devices

With mixer

C700S094000, C369S004000

Reexamination Certificate

active

06330338

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. § 119 of Swiss Patent Application No. 0262/97 filed Feb. 6, 1997, the disclosure of which is expressly incorporated by reference herein in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process and a device for mixing digital audio signals from a first number of inputs to a second number of outputs.
2. Discussion of Background Information
Processes and devices similar in general to the type described above are referred to as digital or digitally operating audio mixers. Digitally operating mixers make it possible to split incoming sound signals into a number of different channels or to transmit them all together to arbitrary outputs. The individual sound signals can be changed and combined with other sound signals. In this manner, each signal may be multiplied by a factor in a conventional manner and added to other signals and possibly to also delay the sound signals.
Known digital mixers include devices having inputs connected in pairs or groups to digital signal processors (DSPs) and positioned to easily perform such operations as addition, multiplication, and storage of sound signals. However, these known digital mixers are limited in that the number of inputs that may be routed to one signal processor it determined by the number of suitable interfaces that are provided. As a result, the desired calculating capacity for many channels can no longer be achieved. This is particular important with sound signals because sound signals contain relatively large quantities of data in particular time periods.
The above-noted problems caused by large quantities of data are usually exacerbated due to the fact that a single signal processor is associated with a small number of inputs. Thus, with a given number of inputs and outputs, a particular number of signal processors, which must be connected in cascade fashion, are necessary. The greatest problem arises in adding up sound signals from a large number of inputs orjust from a number of signal processors of this type in a so-called sum bus.
For this reason, embodiments with so-called “TDM buses” or systems with shared memories, i.e., “shared memory” systems, are known as sum buses. A TDM bus is a parallel bus that prepares a time window for data from each input channel so that the signals in the bus arrive serially, i.e., one after another. It is likewise conceivable to use DPRAM memories for this purpose and to connect the processors to each other like a so-called “daisy chain.” However, each of these embodiments require technical expenditure and are costly.
SUMMARY OF THE INVENTION
present invention provides a process and device for mixing digital audio signals that are significantly simpler and cheaper than those available in the prior art.
In particular, the present invention adds up sound signals from individual inputs or channels with simple circuits or programmable components, e.g., programmable logic components, PLDs, or client-specific integrated circuits ASICs, arranged and utilized for bitwise addition of word and bit synchronized sound signal data streams. Accordingly, the present invention transmits data words with the lowest value bit first, thus, the data streams must be correspondingly formatted. For possible additional processing operations of the signals, i.e., before the addition, a bit-wise multiplication of a relevant data stream may be provided to supply multiple data streams to a summing device. Further, the multiple data streams may be respectively shifted or delayed by one bit with respect to each other. Consequently, the data words of the incoming audio signals are supplied relative to each other so that the data bits arrive, i.e., in increasing order with the lowest value bit first, in parallel data streams that are synchronized word-wise and bit-wise and are added in bit-wise fashion. Accordingly, each output is preceded by a summing circuit that is coupled to at least a part of the outputs via the processing elements.
The advantages achieved by the present invention include that the present device can be embodied or realized in a very reasonably priced manner. One reason for this cost effectiveness is that the addition of data streams requires very little memory. Another reason is that relatively simple and reasonably priced digital signal processors (DSPs) may be used for formatting and for other processing operations on the data from the individual inputs or channels. Provided that a signal processor has a plurality of inputs, a single signal processor can easily operate a number of channels because it only has to perform relatively simple tasks, i.e., because it is no longer necessary for the signal processors to add the data streams. However, the present invention may be arranged such that a signal processor adds the data streams as much as possible so that partial sums are supplied to the summing circuit. This should only occur when the adding can be performed in a single signal processor.
The present invention is directed to a process for mixing digital audio signals from a plurality of inputs into a plurality of outputs. The process includes formatting incoming parallel audio signals composed of data words so that the data words are supplied in an order of lowest value bit to highest value bit, word-wise and bit-wise synchronizing of the formatted parallel audio signals data, and adding the synchronized formatted parallel audio signals in bit-wise fashion.
In accordance with another feature of the present invention, the process further includes selecting one of the formatted incoming parallel audio signals, dividing the one audio signal into a plurality of equivalent parallel signals, forwarding one of the plurality of equivalent parallel signals to a multiplier, and successively bit-wise delaying each of the remaining plurality of equivalent parallel signals. The process also includes forwarding each successively bit-wise delayed parallel signal to a respective multiplier, multiplying the one parallel signal by a lowest bit of a factor for adjusting the one audio signal, multiplying each successively bit-wise delayed parallel signal by a corresponding next bit of the factor, and bit-wise adding the factored one parallel signal and the factored successively bit-wise delayed signals to produce the adjusted one audio signal.
The present invention is directed to a device for mixing digital audio signals that includes a plurality of inputs and a plurality of outputs, a plurality of processing elements, and a plurality of summing circuits. A number of the plurality of inputs includes inputs to the plurality of processing elements and the plurality of outputs include outputs of the plurality summing circuits. Each summing circuit may be coupled with a number of the plurality of processing elements.
In accordance with another feature of the present invention, the summing circuit may include a unit for bit-wise addition beginning with a lowest value bit.
In accordance with another feature of the present invention, the summing circuit may include at least one two-bit or multiple-bit adder.
In accordance with still another feature of the present invention, the summing circuit may include at least three two-bit or multiple-bit adders coupled in cascade fashion.
In accordance with a further feature of the present invention, the processing elements may include a digitally operating signal processor.
In accordance with a still further feature of the present invention, the processing elements may include a summing device, at least one multiplier, and at least one delay unit. Further, the at least one delay unit, the at least one multiplier, and the summing device may be coupled in series for at least one input of the summing circuit.
In accordance with a further feature of the present invention, one or a number of summing circuits form a sum bus for a digitally operating audio mixer.
The present invention may be directed to a process for mixing digital audio signal

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