CODEWITHSUNDEEP
c++audiowavsamplingpcm
mr_hyde
mr_hyde

Reputation: 515

Converting audio samples into an audible file format

I've been trying to convert a huge amount of data (about 900 MB) to an audible file format for a few days now. I've been given a .dat file containing 900 millions floating-point samples (one per line) representing 90 seconds of music at 10 MHz.

I downsampled to 40 KHz but now I don't know how I could possibly listen to the audio hidden in those bytes. I'm writing a C++ program in a Linux environment but if any one knows how to accomplish this task using Matlab, Octave, Python, Audacity, MPlayer or any other tool, please come forth and speak :) Contributions in any amount are greatly appreciated.

    head -n 5 ~/input.dat
    -2.4167
    -7.5322e-016
    -0.2283
     0.13581
    -0.51926

Upvotes: 0

Views: 1716

Answers (4)

Rohan
Rohan

Reputation: 111

WAV allows for floating-point sample data and a wide range of sample-rates (1Hz to 4.2GHz in 1Hz increments, if memory serves).

You don't need to bother with converting to integer values. Just set up the WAV file's header appropriately and write 32-bit floats as binary data in the data section.

From a storage perspective, the 10MHz sample-rate is no problem for a WAV file. Playback, however, will require conversion to something the hardware can handle. The upper limit these days is typically 96 or 192 kHz.

Upvotes: 1

Sriram
Sriram

Reputation: 10578

If you have a sequence of bytes and want to convert it to audio, all you need to do is write a header to it. Since you mentioned that you can use MatLAB, I would recommend wavwrite command. It is simple, tried and tested and excellent for prototyping. Here is the link to the documentation:
http://www.mathworks.in/help/matlab/ref/wavwrite.html

Here are some steps you may need to take in case you are using wavwrite.
- Since your input data is floating point, scale the data in your file to within a range of [-1, 1].
- Once data is scaled plug and chug into the function call.
- Play the wav file using wavplay command.

Upvotes: 1

selbie
selbie

Reputation: 104589

Target your sample rate to 44100 hz (or 48000, 22050, 11025, or 8000 hz)

Convert your audio samples to 16-bit signed integers (-32768 to +32767).

Follow the instructions on WAV file synthesis here: WAV File Synthesis From Scratch - C

Upvotes: 1

Drew Dormann
Drew Dormann

Reputation: 63957

The wav file format is a rather simple one.

You just need to write the 44 byte header block defined in that link, followed by your data converted to integers.

Upvotes: 1

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