KR100717519B1 - Digital audio signal processing apparatus comprising a delay line - Google Patents

Abstract

In the digital audio processing apparatus for the karaoke system, for applications such as echo cancellation, the digital delay line 10 is connected to receive the input audio signal DRY, and before the delayed and filtered signals are combined by the mixer stage 20. , As each signal filter 12, 14 and also has a number of outputs with respective delays for each input signal. Signal filters 12 and 14 are provided by a programmable data processor that receives delay line outputs and processes each according to the respective current filter settings SE and SC. Upon receiving a command to change the filter setting (SC) for a particular delay line output, the processor generates the second filter 114 for output with the new setting (SF) in parallel with the first filter (14). And filter the output of both new settings and output signal fading from the first output to the second filter output. To avoid processing overload, the processor generates only as many individual parallel filters 114 as can be accommodated at a time within a predetermined limit of the processor's data processing capability, setting the filters one at a time or in small groups. Change them effectively.

Signal fading, digital audio signals, delay lines, karaoke systems, parallel filters

Description

Digital audio signal processing apparatus comprising a delay line

The present invention relates to the processing of digitized audio signals, and in particular, but not by way of limitation, to the processing of processor resources during the addition of echo or echo effects by such processing.

One example of an audio signal processor is given in US Pat. No. 5,774,560, which involves a processing echo network comprising a plurality of wave-ladder filters, each filter corresponding from a wavelength propagation in a selected direction. Simulate a reflected audio signal. Each such filter receives as an input a signal derived from the original audio signal, and the output of the filter is coupled to the adder to produce an echo effect.

Other examples can be found in the field of karaoke systems where echo / echo effects are often applied to the signal from the singer's microphone. The effect is a typically unmodified signal (so-called "dry" signal) summed with additional signal components formed from filtered and delayed versions of the weighted total dry signal, filtering to provide echo, and delay to provide echo. ) Such a system is described herein with reference to FIG. 1 of the accompanying drawings.

As can be readily appreciated, filtering can be applied to the digitized data by one or more suitably programmed processors that can change the applied processing in response to a user or system command. However, filtering can prove to be relatively arithmetic expensive, and for relatively low power systems, the processor will operate at or near peak capacity for most of the time. Unless specific methods are provided to avoid it, the configuration changes of the filters cause unacceptable delays when the processor runs out of capacity to process real-time change instructions, resulting in an audible "clicks" appearing in the output signal. Or a stronger processor should be used with the ability to handle these short-term requests for additional processing power.

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It is therefore an object of the present invention to provide an audio signal processing apparatus having a plurality of programmable filters that avoids audio discontinuities when the filter settings change.

Another object is to provide an apparatus that may achieve this without requiring excessive processor capacity for the filters.

According to the present invention, there is provided a digital audio signal processing apparatus, wherein the apparatus,
A digital delay line connected to receive an input audio signal and having a plurality of outputs, each of the outputs having a respective delay relative to the input signal,

Respective signal filters coupled to respective delay line outputs, each signal filter having at least one variable setting, and

A mixer stage arranged to receive and combine the outputs of the signal filters and to output a processed audio signal,

The signal filters are provided by a programmable digital data processor arranged to receive the delay line outputs to process each of the outputs in accordance with a respective current filter setting and to change the filter setting for a particular delay line output. Upon receiving, the processor generates a second filter for the corresponding output in parallel with the first filter to filter the output at both the old and new settings, at the new setting, and from the first to the second filter. Outputs a signal fading to the output. By the creation of the second filter, a smooth transition between the settings may be made.

When receiving instructions to change the plurality of filter settings for respective delay line outputs such that this generation of additional filters during the duration of the configuration change does not produce excessive processing of overheads, the processor preferably provides the processor. It is programmed to produce only as many respective parallel filters as can be accommodated at a time within predetermined limits on the data processing capability of the circuit. In particular in a processor-limited embodiment, the processor may in turn change the settings of the filters, including the generation of respective parallel filters and fading between their outputs.

The apparatus may also include two or more audio signal inputs each having a respective delay line, the output filters for all the delay lines being provided by the same processor, the processor being configured for only one of the delay lines. It is arranged to allow changes to filter settings simultaneously-also to avoid overloading the processor. If all filter settings are not changed at the same time, the apparatus may further comprise storage means for holding an instruction queue in which the instructions are arranged to change one or more filter settings that do not act immediately.

The apparatus may further comprise user-operable input means coupled with the processor and capable of directly or indirectly specifying changes to one or more filter settings. A mixer stage is also coupled to receive the input signal or each input signal, arranged to combine it with an output of a signal filter to output the processed audio signal and / or to receive one or more other digital audio signals. And the output of the signal filter and the signal or each such signal to output the processed audio signal.

Other features and advantages of the invention will be apparent from the following description of the preferred embodiments of the invention, given by way of example and by reference to the accompanying drawings, in which: FIG.

1 is a schematic diagram illustrating a multiple output digital delay line with an output filter on each output for generation of echo and echo effects.

2 is a block schematic diagram of a data processing apparatus suitable for practicing the present invention.

3 to 6 are views continuously showing a change of filter setting in the apparatus implementing the present invention.

FIG. 7 illustrates a sequential processing of a filter change operation with multiple delay lines. FIG.

In the following description, a dual microphone karaoke system embodying the present invention will be described with reference to the attached figures 1 to 7; However, it will be appreciated that the present invention is not limited to such applications and may be used in other digital audio signal processing systems, such as echo cancellation circuits, in telecommunication applications as will be readily appreciated by those skilled in the art.

As mentioned above, in karaoke systems, echo and / or echo effects are often applied to the microphone input. As shown in Fig. 1, this effect is such that the dry signal (analog digital conversion and, if necessary) summed with an additional signal component formed from the weighted sum of the filtered and delayed versions of the dry signal. By forming an OUT signal consisting of a microphone output, such as other localized signal processing. The echo is inserted as well as four incremental delay values, D (1), D (2), D (n-1), and D (n) (other values between D (2) and D (n-1)). Tapping the output shown to pass the dry signal through a multi-tap delay line 10 where the amount of available delay varies from T = 0 (no delay) to T = End (maximum delay). Done. On each of these outputs, respective filter stages 12 (F1), 14 (F2), 16 (Fn-1), 18 (Fn) provide an echo effect, each filter having its respective initial setting. (18 (SA), 16 (SB), 14 (SC) and 12 (SD)). To produce the output signal OUT, the outputs from the filter stages 12, 14, 16, 18 are summed by the mixer 20 together with the dry signal.

As shown, the memory 22 operating as a queue Q or buffer for user or system commands (UIP) to change one or more filter settings (SA, SB, SC, SD) has its own filter stage. (12, 14, 16, 18).

2 shows the functional components of a device embodying the invention in a twin-microphone karaoke device. Each two microphones 24 and 26 output their signals to respective analog-to-digital (A / D) converters 28 and 30, from which each digital bit stream is associated with a respective multi-tap random access memory (MEM). (32, 34)). Each of these memories MEM is connected with a programmed digital data processor PROC 36, and after it is read, it is determined at a predetermined number of times D (1), D (2) ... D (n). Reading through the content to form each digital delay line. As shown, the processor 36 may be a slave unit operating under the control of a central control and processing unit (CPU) 38 for the apparatus as a whole, or the processor 36 functionality may be a dedicated subset of processor functionality. It can be executed by the CPU 38 as a (subset).

The processor stage 36 applies the processing specified for each filter stage 12, 14, 16, 18 to the digital data read from the memories 32, 34, and as a digital audio stream to the mixer stage 40. Outputs: In the case of mixer 20 in the embodiment of FIG. 1, the output signal is routed directly to mixer 40 directly through memory 32 or 34 and through processor 36 without delay ( Or dry) input signal components.

Also, the source of the background music read out from the optical disc 42 is connected as input to the mixer 40 for the karaoke embodiment shown, so that the user of the microphones 24 and 26 sing along with the music: on the display screen. The visual display of lyrics for a singer is a known feature of such a system and is no longer shown or described since it is not related to the operation according to the requirements of the present invention.

The required track of background digital audio that the user wishes to sing along is directed to the device by user input control 44, and as will be readily understood, the control may be selected from a menu, one from a group or from a touch screen display or Alternatively, you can include the input of an alphanumeric code to indicate the selection. After selection, the digital audio is read from the disc 42 by the disc reader 46 under the instruction of the system (CPU 38). When the audio on the disc is typically in encoded format (eg MPEG), the digital audio read by the reader 46 is properly passed through the decoder stage 48 into the buffer 50 in a decoded form before being read. do. From the buffer 50, any necessary signal processing, such as pitch shifting 52, is applied under the guidance of the CPU 38 before background audio is added to other components for the mixer 40.

From mixer 40, the output digital audio signal is subjected to any other signal processing required before it is output from amplifier 56 and each of left and right speakers 58 and 60 therefrom: Amplifier 56 is a digital signal amplifier. Note that a separate digital analog (D / A) stage is not shown since it is assumed.

An arrangement for setting one or more filters (12, 14, 16, 18 of FIG. 1) and changing its setting will be shown with reference to the subsequent figures of FIGS. In FIG. 3, a command (UIP) to change settings is received and queued in the buffer 22. The change instruction is due to a problem with the execution of routines for the system or the limitation of the available processor capacity of the processor (38 in FIG. 2) that is passed to the affected filters (F1, F2 in this example) and hosts the filters. It is determined to change the setting continuously.

4 illustrates a situation in which the setting SD of the filter F1 is changed to the setting SE. The change involves generation by the hosting processor of the second F1 filter 112 in parallel with the first 12 at the new setting SE, where the second filter is the new setting SE. The signal tapped from the delay line 10 is a copy of the filter, or as indicated by arrow 62, the crossfade is given a flat change from the first setting SD to the second setting SE. Is applied to the mixer 20 on the output.

In Fig. 5, the change from the settings for the F1 filter (SD to SE) is terminated, and the copy 12 of the filter in the SD setting is deleted. The next (F2) filter 14 changes from the settings SC to SF, and again the parallel filter 114 is created at the new setting. Also, as described above, there is a cross fade (indicated by arrow 64) to give a smooth transition between settings.

In Fig. 6, the setting change is terminated, and only such a copy of the filters F1 and F2 is maintained in the new setting SE and SF respectively. As is evident from the progress of Figures 3 to 6, overload is avoided by scheduling filter changes that occur continuously in the processing power required. Filters cannot be changed into small groups (possibly two or three filters) at the same time, as long as there is sufficient processing power to manage multiple filters and actions to change settings without unacceptably slowing it. The groups are processed in succession.

In general, it is desirable to continuously change individual filter settings to put a load on the processor. This may also be applied in the situation as shown in FIG. 7 where there are two delay lines 10, 110 (individual ones of the microphones MIC1, MIC2 respectively), the first two line taps of the delay line 10. It is desirable to change the settings for filter 72, 74 on the first two taps of filter 12, 14 and second delay line 110 on. As long as the filters are all provided by the same processor, a rule that only one can be changed at a time is applied, the filters are processed in the order of 12, 14, 72, 74, and all the settings for the delay line 10 output. Before the setting for the delay line 110 output, all the settings for the delay line 10 output are changed.

By reading this specification, other changes, including or consistent with other optical or magnetic disk recording standards, will be apparent to those skilled in the art. Such modifications may involve other features that are already known in the art of playback devices for audio and / or video signals and components thereof and that may be used instead of or in addition to the features already described herein.

Claims (8)

A digital audio signal processing device, The device, A digital delay line 10 connected to receive an input audio signal DRY and having a plurality of outputs, each of the outputs having a respective delay relative to the input signal, Respective signal filters 12, 14, 16, and 18 coupled to respective delay line outputs, each signal filter having at least one variable setting, and A mixer stage 20 arranged to receive and combine the outputs of the signal filters 12, 14, 16, 18, and to output the processed audio signal, The signal filters 12, 14, 16, 18 are received by a programmable digital data processor 36, 38 arranged to receive the delay line outputs and process each of the outputs according to respective current filter settings. And upon receiving instructions to change the filter setting for a particular delay line output, the processor generates a second filter 112 for that output in parallel with the first filter 12, in the new setting, In the digital audio signal processing apparatus, filtering the output in both the conventional and new settings, and outputting a signal fading from the first filter 12 to the output of the second filter 112, Upon receiving instructions that change the plurality of filter settings for each delay line outputs, the processor 36, 38 may be accommodated at one time within predetermined limits on the data processing capability of the processor 36, 38. And arranged to produce only as many respective parallel filters as there are. delete The method of claim 1, Upon receiving instructions to change a plurality of filter settings for respective delay line outputs, the processor 36, 38 includes in turn fading between the generation of respective parallel filters and their outputs, in turn. Digital audio signal processing apparatus. The method according to claim 1 or 3, Further comprising two or more audio signal inputs MIC1, MIC2 having respective delay lines 10, 110, the output filters for all delay lines being provided by the same processor 36, 38, The processor (36, 38) is arranged to allow changes to filter settings for only one of the delay lines at the same time. The method of claim 4, wherein Storage means (22) for holding an instruction queue in which instructions for changing one or more filter settings that are not immediately activated are arranged. The method according to claim 1 or 3, Further comprising user-operable input means (44) coupled with the processor and capable of directly or indirectly specifying changes to one or more filter settings by the user. The method according to claim 1 or 3, The mixer stage 20 is also coupled to receive the input signal or each input signal DRY and the outputs of the signal filters 12, 14, 16, 18 to output the processed audio signal. And arranged to combine the input signals. The method according to claim 1 or 3, The mixer stage 20 is also coupled to receive one or more other digital audio signals and the outputs of the signal filters 12, 14, 16, 18 and the signal or each such to output the processed audio signal. And arranged to combine the signals.

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