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I have a PCM datafile that I know is valid. I can play it, edit it into pieces, etc. and it will always play, as well as the individual pieces.

But when I try to translate it into shorts from bytes 

bytes[i] | (bytes[i+1] << 8)

The file is 16 bit, single channel and 44100 sampling. I don't see anything that looks like a wave file visually.

As a test I record led among silencer with one very loud sound in the middle. Still the chart I made from my intake looked like every other chart when I try this. Am I somehow doing this wrong? Or misunderstanding what I'm reading/attempting?

All am looking to do is detect a very low threshold to find a word gap.

Thanks

comrade
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Daniel Kaplan
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1 Answers1

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My psychic powers suggest this is a big-endian vs little-endian thing.

If the source file stores samples in big-endian, this is likely what you want:

(bytes[i] << 8) | (bytes[i+1])

For what it's worth, WAV files are little-endian.

Other possibilities include:

I don't see your code, but maybe your code is only incrementing i by 1 instead of 2 on every loop iteration. (A common mistake I've made in my own code).

signed types or casting. Be explicit how you do the bit operations with respect to signed vs. unsigned. I'm not sure if "bytes" is an array of "unsigned char" or "char". Nor am I sure if "char" defaults to signed or unsigned. This might be better:

unsigned char b1 = (unsigned char)(bytes[i]);
unsigned char b2 = (unsigned char)(bytes[i+1]);
short sample = (short)((b1 << 8) | (b2));
selbie
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