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Abstract: The integrated real-time voice processing chip SD771D is a single-chip voice processor introduced by Taiwan Xiangyin Technology Co., Ltd. The chip can transpose the output speech (such as raising and lowering), and can also convert the voice of male and female voices to each other. This paper introduces the working principle and application of the chip, and gives the hardware interface circuit of the typical application of SD771D.
Keywords: real-time diacritical SD771D typical application circuit
1 Overview
Speech techniques include speech recognition, speech synthesis, and text-to-speech TTS (Text? To? Speech). At present, speech synthesis technology is in a mature development period, both in research and in application, and some have already been put into practical application. Taking TTS technology as an example, this technology and related products have been promoted by many manufacturers, such as the software-only TTS processing software package (ie, SAPI SDK software package) introduced by Microsoft; the voice processing chip WTS701 and ISD introduced by Winbond Electronics Series of voice processing products, etc.
SD771D is a single-chip real-time accented processor introduced by Taiwan Xiangyin Technology Co., Ltd., which uses real human voice as a sample, which can transform the output speech in real time (such as raising and lowering), and can also interpret the voices of male and female voices in real time. Conversion. It can be used to create a variety of virtual characters, create a changing audio environment, and better entertainment.
2 SD771 features and working principle
2.1SD771 features
â—‡ Built-in microphone amplifier circuit;
◇ Built-in 32 Ω speaker drive circuit;
â—‡ Built-in digital level control (15 levels) circuit;
å¯é€‰æ‹© You can select the digital or analog input mode to change the pitch;
â—‡ The digital input mode is 15 tone changes;
â—‡ The analog input mode is 180 pitch changes;
◇ Built-in 16-bit ΔΣ A/D and D/A converter;
â—‡ Built-in anti-noise digital filter;
â—‡ Operating voltage range is DC+3.6~+6.0 V;
â—‡ Operating current is 25 mA;
â—‡ Immediately convert the speaker's voice into a different tone output (eg, the pitch becomes higher and lower, and the male and female voices are converted).
Figure 1 shows the internal structure of the SD771D. The BPF (Band Pass Filter) and LPF (Low Pass Filter) are anti-noise digital filters. In Figure 1, GAIN_INC is the volume up button, GAIN_DEC is the volume down button, PITCH_INC is the pitch up button, PITCH_DEC pitch down button, ORIG is the restore tone button, and RESET is the reset button. All of the buttons described above are active low, each button must be pressed for a duration greater than 10 ms, and the time between two different button presses must be greater than 60 ms, as shown in Figure 2. PITCH_VR is the input of the analog mode change tone, and XI and XO are used to connect the input of the system crystal circuit.
2.2SD771D working principle and typical application circuit
(1) Change the level of sound tuning
The sound input from the microphone is sent by the DAC after being processed by the SD771D. The SD771D simultaneously sends two signals, one for the digital signal and the other for the analog signal, and used to change the level of the sound tuning. When the level of PITCH_VR is less than 0.1 V, the digital signal channel is turned on and the analog signal channel is turned off. The regulation of the sound signal level of the digital signal channel and the analog signal channel is independent of each other.
(2) Digital signal channel
The digital signal channel is controlled by PITCH_INC (tone up button) or PITCH_DEC (tone down button). When the level of PITCH_VR is less than 0.1 V, the level of sound tuning is controlled by PITCH_INC or PITCH_DEC. At this point, the SD771D will repeatedly check the status of PITCH_INC and PITCH_DEC. When one of the two buttons has a low-level pulse, the SD771D will immediately change the level of the sound tuning. The level of sound tuning has 7 levels of upshift and downshift, including the normal tone level when no key is pressed, a total of 15 levels, as listed in Table 1.
(3) Analog signal channel
The SD771D has an 8-bit analog-to-digital converter (ADC) inside. The input analog signal voltage is usually controlled by the PITCH_VR terminal for sound level adjustment. If the voltage on PITCH_VR is between 0.3 and 2.2 V, then the value of this voltage range is divided into 180 levels, and each level corresponds to a tone ratio.
Figure 3 shows a typical application circuit for the SD771D.
Figure 3 Typical circuit of SD771D
Conclusion
The SD771D can transpose the output speech in real time (such as raising and lowering), and process the transposition technology according to the level of sound tuning, and can also convert the voices of male and female voices into each other in real time.
references
1 Sounding Technology Inc. SD771D datasheet. 2005
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