Make detection sample rate constant: 44100, resample if necessary.

Signed-off-by: Stefan Westerfeld <stefan@space.twc.de>

src/Makefile.am

@@ -3,7 +3,7 @@ bin_PROGRAMS = audiowmark
 COMMON_SRC = utils.hh utils.cc convcode.hh convcode.cc random.hh random.cc
 
 audiowmark_SOURCES = audiowmark.cc wavdata.cc wavdata.hh fft.cc fft.hh $(COMMON_SRC)
-audiowmark_LDFLAGS = $(SNDFILE_LIBS) $(FFTW_LIBS) $(LIBGCRYPT_LIBS)
+audiowmark_LDFLAGS = $(SNDFILE_LIBS) $(SAMPLERATE_LIBS) $(FFTW_LIBS) $(LIBGCRYPT_LIBS)
 
 noinst_PROGRAMS = testconvcode testrandom
 

src/audiowmark.cc

@@ -11,6 +11,8 @@
 #include "convcode.hh"
 #include "random.hh"
 
+#include "samplerate.h"
+
 #include <assert.h>
 
 #include "config.h"
@@ -42,6 +44,7 @@ namespace Params
   static double sync_threshold2  = 0.7; // minimum refined quality
 
   static size_t frames_pad_start = 250; // padding at start, in case track starts with silence
+  static int    mark_sample_rate = 44100; // watermark generation and detection sample rate
 
   static int test_cut            = 0; // for sync test
 }
@@ -1073,7 +1076,35 @@ get_watermark (const string& infile, const string& orig_pattern)
       fprintf (stderr, "audiowmark: error loading %s: %s\n", infile.c_str(), wav_data.error_blurb());
       return 1;
     }
-  return decode_and_report (wav_data, orig_pattern);
+  if (fabs (wav_data.mix_freq() - Params::mark_sample_rate) > 0.1)
+    {
+      printf ("sample rate: %f -> autoconvert\n", wav_data.mix_freq());
+
+      double ratio = double (Params::mark_sample_rate) / wav_data.mix_freq();
+
+      const vector<float>& in = wav_data.samples();
+      vector<float> out (lrint (in.size() / wav_data.n_channels() * ratio) * wav_data.n_channels());
+
+      SRC_DATA data;
+      data.data_in = &in[0];
+      data.data_out = &out[0];
+      data.input_frames = in.size() / wav_data.n_channels();
+      data.output_frames = out.size() / wav_data.n_channels();
+      data.src_ratio = ratio;
+      if (src_simple (&data, SRC_SINC_MEDIUM_QUALITY, wav_data.n_channels()) != 0)
+        {
+          fprintf (stderr, "audiowmark: resampling error occurred\n");
+          return 1;
+        }
+
+      WavData resampled_data (out, wav_data.n_channels(), Params::mark_sample_rate, wav_data.bit_depth());
+
+      return decode_and_report (resampled_data, orig_pattern);
+    }
+  else
+    {
+      return decode_and_report (wav_data, orig_pattern);
+    }
 }
 
 int