I haven’t received an answer to my previous question, but after thinking about it a bit, I only have one real question :
When the DSP callback function is called for a Stream DSP, can I determine the position in the stream (in samples or milliseconds) of the first sample passed to the callback function?
I need this so I can sync some visuals with the sound (a spectrum analyzer, but seperate for each stream).
- Adion asked 16 years ago
I think I will have to know the samples since the song start, because what I wanted to do wa compare this value with GetPosition, so I know when the samples are actually played.
So I would have a buffer with the samples since song start and some matching visualisation, and then I compare to this value with GetPosition to know which buffer I have to show.
Will it be correct when I set my counter to the same value I passed to SetPosition, or will it align on mpeg frames,…?
I’ve got it working!
I count the samples as you said, and I compare this count with (FSOUND_Stream_GetPosition – 125) to get the correct buffer.
I don’t really know why -125 (maybe a buffer length + fmod’s mixing buffer)
When I compared the counted samples with FSOUND_Stream_GetPosition, GetPosition would always be ahead about 125ms.
Now my Visualisation is good, but my beat detection isn’t.
When I use my beat detection algorithm on fmod’s FFT data, I get the correct beats in about 10-20 seconds, but when I use my own FFT, it doesn’t really get it.
I’ve compared both FFT outputs and they differ indeed.
My FFT uses 1024 samples, and is multiplied with a sine as windowing function.
I store the time for each block of FFT, so the accuracy is about 25 ms.
When that didn’t gave the correct results, I tried overlapping buffers, so the last 512 samples and the first 512 samples of the next block combine to another buffer, so I have an FFT every 12 ms.
Still I don’t get the same results as fmod.
Any chance you could give me your fft source, or tell me what windowing function you used, and maybe what normalization function?
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