Looking for a WAV to ADPCM2 audio converter SDK. Preferably written in.NET, though ActiveX or standard DLL (that can be PInvoked from.NET) is suitable as well. The ADPCM2 format was created by OKI and is used in some mobile devices, and shouldn't be confused with the ADPCM or VOX formats, which I believe differ slightly. ACM Converter 3.2 is software that allows you to convert ACM and PCM WAV files from one format to another. Add the audio files you wish to convert by adding them from the dialog box or by dragging. Best way to convert your WAV to IMA file in seconds. 100% free, secure and easy to use! Convertio — advanced online tool that solving any problems with any files. Best way to convert your WAV to IMA file in seconds. 100% free, secure and easy to use! Convertio — advanced online tool that solving any problems with any files.
PCM vs DPCM vs ADPCM-Difference between PCM,DPCM,ADPCM modulations
This page on PCM vs DPCM vs ADPCM describes difference between PCM, DPCM and ADPCM modulation techniques.All these are pulse digital modulation techniques.
PCM
The short form of the Pulse Code Modulation is PCM. In PCM, the analog speech waveform is sampled and converted directly intoa multibit digital code by an Analog to Digital converter.The digital code is stored in the memory and which is later re-called for theplayback.
In this type of modulation, analog data is sampled and quantized before being represented to digital binaryform. Hence using PCM, continuous amplitude and continuous time signal waveform is converted into discrete amplitude and discrete timewaveform.
If there is a n bit quantizer and sampling rate is Fs then bit rate will be
Rb(bits/sec) = n * Fs
Sampling rate must be at a rate greater than or equal to nyquist rate to avoid aliasing.Higher the sampling rate easier is the reconstruction at the receiver.Bandwidth requirement is minimum Rb/2 and maximum Rb.
Signal to Quantization Noise Ratio for PCM for sinusoidal input is
SQNR (dB) = 6*n + 1.76, where n is bit of uniform quantizer.
DPCM
The short form of Delta Pulse Code Modulation is DPCM.In DPCM, a multi-bit difference value is stored.A bipolar D/A converter is used for playback to convert the successive difference valuesto an analog waveform.
Figures 1 and 2 depicts DPCM encoder and DPCM decoder block diagram.
This modulation scheme encodes difference in current as well as predicted values.
Simple block diagram of linear predictor used in DPCM is depicted in the fig3.
When the samples of a signal are highly correlated then we go for DPCM in order to save bandwidth or usingthe same bandwidth at higher data rate.
Delta Modulation
It is a special case of differential PCM.It is called 1 bit DPCM as it transmits only one bit per sample.
In delta modulation problem of slope overload occurs if input is changing very fast that is :
| Δ/Ts | < | dm(t)/dt |
To overcome slope overload error we choose optimum size of Δ such that :
Δopt/Ts = | dm(t)/dt |max
For m(t) = Am*cos(2*π*fm*t)
Δopt/Ts = 2*π*fm*Am
The second problem occurs is hunting, which occurs when message is almost constant.
ADPCM
In adaptive delta modulation, step size is chosen in accordance with message signal sampled value to overcomeslope overload error and hunting.
If message is varying at a high rate then step size is high and if message is varying slowly then step size is small.
The short form of Adaptive Delta Pulse Code Modulation is ADPCM.In ADPCM, a difference value that has been mathematically adjusted accordingto the slope of the input waveform is stored. Bipolar D/A converter is used to convert the stored digital codeto analog for playback.
Figures 4 and 5 depicts ADPCM encoder and ADPCM decoder block diagram.
Refer advantages and disadvantages ofPCM >>,DPCM >> andADPCM >> techniques.
Modulation types
BPSK -This page describes BPSK modulation technique with equation and constellation diagram.
QPSK -This page describes QPSK modulation technique with equation and constellation diagram.
QAM-This page describes QAM modulation technique with equation and constellation diagram.
MSK-GMSK MSK modulation,GMSK modulation and GMSK demodulation.
8PSK 8-PSK modulation or multilevel PSK or phase shift keying modulation technique.
BPSK vs QPSK -Difference Between BPSK and QPSK modulation techniques.
QPSK vs OQPSK vs pi/4QPSK-Difference between QPSK,OQPSK and pi/4QPSK modulation techniques
Differential Encoder and Decoder
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Ima Adpcm
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