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foobar2000/helpers/VisUtils.cpp

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+#include "stdafx.h"
+
+#include "VisUtils.h"
+
+namespace VisUtils {
+	void PrepareFFTChunk(audio_chunk const & source, audio_chunk & out, double centerOffset) {
+		const t_uint32 channels = source.get_channel_count();
+		const t_uint32 sampleRate = source.get_sample_rate();
+		FB2K_DYNAMIC_ASSERT( sampleRate > 0 );
+		out.set_channels(channels, source.get_channel_config());
+		out.set_sample_rate(sampleRate);
+		const t_size inSize = source.get_sample_count();
+		const t_size fftSize = MatchFFTSize(inSize);
+		out.set_sample_count(fftSize);
+		out.set_data_size(fftSize * channels);
+		if (fftSize >= inSize) { //rare case with *REALLY* small input
+			pfc::memcpy_t( out.get_data(), source.get_data(), inSize * channels );
+			pfc::memset_null_t( out.get_data() + inSize * channels, (fftSize - inSize) * channels );
+		} else { //inSize > fftSize, we're using a subset of source chunk for the job, pick a subset around centerOffset.
+			const double baseOffset = pfc::max_t<double>(0, centerOffset - 0.5 * (double)fftSize / (double)sampleRate);
+			const t_size baseSample = pfc::min_t<t_size>( (t_size) audio_math::time_to_samples(baseOffset, sampleRate), inSize - fftSize);
+			pfc::memcpy_t( out.get_data(), source.get_data() + baseSample * channels, fftSize * channels);
+		}
+	}
+
+	bool IsValidFFTSize(t_size p_size) {
+		return p_size >= 2 && (p_size & (p_size - 1)) == 0;
+	}
+
+	t_size MatchFFTSize(t_size samples) {
+		if (samples <= 2) return 2;
+		t_size mask = 1;
+		while(!IsValidFFTSize(samples)) {
+			samples &= ~mask; mask <<= 1;
+		}
+		return samples;
+	}
+};