fix: Replace deprecated FFmpeg avfft.h APIs

src/spek-fft.cc

@@ -2,7 +2,13 @@
 
 #define __STDC_CONSTANT_MACROS
 extern "C" {
+#include <libavutil/version.h>
+#if LIBAVUTIL_VERSION_INT >= AV_VERSION_INT(58, 18, 100)
+#define USE_LIBAVUTIL_TX_API
+#include <libavutil/tx.h>
+#else
 #include <libavcodec/avfft.h>
+#endif
 }
 
 #include "spek-fft.h"
@@ -16,26 +22,46 @@ class FFTPlanImpl : public FFTPlan
     void execute() override;
 
 private:
+#ifdef USE_LIBAVUTIL_TX_API
+    struct AVTXContext *cx;
+    av_tx_fn tx_func;
+#else
     struct RDFTContext *cx;
+#endif
 };
 
 std::unique_ptr<FFTPlan> FFT::create(int nbits)
 {
     return std::unique_ptr<FFTPlan>(new FFTPlanImpl(nbits));
 }
 
-FFTPlanImpl::FFTPlanImpl(int nbits) : FFTPlan(nbits), cx(av_rdft_init(nbits, DFT_R2C))
+FFTPlanImpl::FFTPlanImpl(int nbits) : FFTPlan(nbits)
 {
+#ifdef USE_LIBAVUTIL_TX_API
+    const float scale = 1.f;
+    av_tx_init(&this->cx, &this->tx_func, AV_TX_FLOAT_RDFT, 0, 1 << nbits, &scale, AV_TX_INPLACE);
+#else
+    this->cx = av_rdft_init(nbits, DFT_R2C);
+#endif
 }
 
 FFTPlanImpl::~FFTPlanImpl()
 {
+#ifdef USE_LIBAVUTIL_TX_API
+    av_tx_uninit(&this->cx);
+#else
     av_rdft_end(this->cx);
+#endif
 }
 
 void FFTPlanImpl::execute()
 {
+#ifdef USE_LIBAVUTIL_TX_API
+    float *input = this->get_input();
+    this->tx_func(this->cx, input, input, sizeof(float));
+#else
     av_rdft_calc(this->cx, this->get_input());
+#endif
 
     // Calculate magnitudes.
     int n = this->get_input_size();

src/spek-fft.h

@@ -26,7 +26,7 @@ class FFTPlan
     {
         // FFmpeg uses various assembly optimizations which expect
         // input data to be aligned by up to 32 bytes (e.g. AVX)
-        this->input = (float*) av_malloc(sizeof(float) * input_size);
+        this->input = (float*) av_malloc(sizeof(float) * (input_size + 2));
     }
 
     virtual ~FFTPlan()