Questions tagged [pcm]

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UART signal recovery from PCM data

I have a PCM signal recording of UART data after high-pass filter. The recording looks like this: I know baud rate and parity setting beforehand. What algorithm could help me recover actual binary ...
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24 views

How to scale audio signal from PCM data to a dB SPL value?

I've got a set with MEMS microphones that measure audio signals at ultrasonic frequencies. The MEMS microphones have a PDM output which is then converted into PCM (this is necessary to allow for a ...
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1answer
58 views

What is causing these spikes in the output of the low pass filter?

I am low pass filtering the PCM of an arbitrary Bell 103 (300 bps) signal. However, the output of the low pass filter shows random spikes in amplitude. I have tried to increase the bandwidth, but no ...
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1answer
31 views

Carrier frequency offset in Bell 103 FSK system

This question is a sequel of the discussion that started in this question. Dan Boschen suggested some very nice solutions to decode a Bell 103 FSK signal. I am especially interested in decoding the ...
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1answer
160 views

Decoding a PCM BFSK signal (Bell 103)

A recent project requires me to get into some basic DSP, in C. I receive PCM samples of a BFSK signal (Bell 103). The sample rate is 8 kHz. The mark and space frequencies are 1070 and 1270 Hz. To ...
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19 views

Generate PCMU/PCMA noise samples

I'm attempting to test an Real-time Protocol library and would like to be able to transmit white noise. The part of the library I'm testing doesn't have access to the codecs. How do I generate PCMU ...
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1answer
101 views

Analyze PCM data

I am getting some 16 bit PCM data (raw bits) from a serial port . I need to collect this stream of bits using some python application running in PC and store it somewhere(Assume it in an array). I ...
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1answer
35 views

Digital Audio Mixing Fundamental. What will be the data rate of mixed audio?

I have voice data at 128 kbps coming from three different sources. I'm looking for mixing all three voices together and sending it back to speakers. What methodologies are there for mixing digital ...
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1answer
32 views

What are the definitions of symbols and samples related to PCM?

What are the definitions of symbols and samples related to PCM? For example in binary encoding $\{0,1\}$ with 8 levels of quantization, is one symbol either of $ \ 0 \ or \ 1\ $? or is it the ...
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1answer
1k views

Nyquist Maximum data rate formula for PCM

The Nyquist maximum data rate formula for a binary PCM is given by $$C = 2B\log_2L$$ I'm not very sure what "$B$" is here. Is it the bandwidth of the signal being sampled or is it the channel ...
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0answers
30 views

Number of binary digits in PCM

This is the problem from Shaum Otlines Analog and Digital Communications, Hwei Hsu Problem 5.13. It asks for number of binary digits in each sample if each sample at the receiving end of the system ...
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1answer
175 views

Error reading a .PCM file

I want to convert a .wav file with a sampling frequency of 44100 Hz to a 16 depth .pcm. I don't why I'm getting those peaks at the beginning of .pcm plot (second figure below 2). If you could ...
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1answer
1k views

Minimum Channel Bandwidth for PCM

Please check if my answer to GATE IN 2010 question 11.20 is correct/can be improved upon. So, every $\frac{1}{f_s}$ sec, a sample is taken. The signal amplitude is quantized into $2^n$ levels such ...
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1answer
186 views

Windows Audio WAVEFORMAT buffer BYTE to 16-bit int

I am trying to understand audio-buffer processing at the low-level for the first time. I have the following C++ code copying WAVE-format byte data from capture buffer of Window Core Audio (*ppData in ...
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1answer
6k views

How to get the volume level from PCM audio data?

I have a decoded PCM audio data obtained from the Web Audio API. I'd like to generate a chart that represents the volume level (perceived by humans) over time. ...
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1answer
3k views

why companding is used?

Which one is the best answer? Companding is used [] ...
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2answers
950 views

How to mix 8bit/8kHz unsigned linear PCM data in AppsScript?

I am having the most difficult time mixing simple unsigned 8-bit/8kHz linear PCM audio samples in JavaScript (AppsScript). I've tried all the basic maths listed here, employing basic number arrays. ...
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1answer
605 views

How is a PCM byte converted to a voltage level?

16-bit signed PCM would have possible values of ~-32,000 to ~+32,000. How is this value converted to a voltage level for the speaker? If a DAC outputs 5VAC, the values would be ~+-5v. How is the ...