Switch between audio channels

References #18.

MANUAL.md

@@ -47,6 +47,9 @@ On OS X use the Command key instead of Ctrl.
 
 ## Spectrogram
 
+`c`, `C`
+:   Change the audio channel.
+
 `f`, `F`
 :   Change the DFT window function.
 

src/spek-pipeline.cc

@@ -25,6 +25,7 @@ struct spek_pipeline
 {
     std::unique_ptr<AudioFile> file;
     std::unique_ptr<FFTPlan> fft;
+    int channel;
     enum window_function window_function;
     int samples;
     spek_pipeline_cb cb;
@@ -61,6 +62,7 @@ static void reader_sync(struct spek_pipeline *p, int pos);
 struct spek_pipeline * spek_pipeline_open(
     std::unique_ptr<AudioFile> file,
     std::unique_ptr<FFTPlan> fft,
+    int channel,
     enum window_function window_function,
     int samples,
     spek_pipeline_cb cb,
@@ -70,6 +72,7 @@ struct spek_pipeline * spek_pipeline_open(
     spek_pipeline *p = new spek_pipeline();
     p->file = std::move(file);
     p->fft = std::move(fft);
+    p->channel = channel;
     p->window_function = window_function;
     p->samples = samples;
     p->cb = cb;
@@ -95,7 +98,7 @@ struct spek_pipeline * spek_pipeline_open(
         p->input_size = p->nfft * (NFFT * 2 + 1);
         p->input = (float*)malloc(p->input_size * sizeof(float));
         p->output = (float*)malloc(p->fft->get_output_size() * sizeof(float));
-        p->file->start(0, samples);
+        p->file->start(channel, samples);
     }
 
     return p;
@@ -196,8 +199,8 @@ std::string spek_pipeline_desc(const struct spek_pipeline *pipeline)
     if (pipeline->file->get_channels()) {
         items.push_back(std::string(
             wxString::Format(
-                ngettext("%d channel", "%d channels", pipeline->file->get_channels()),
-                pipeline->file->get_channels()
+                // TRANSLATORS: first %d is the current channel, second %d is the total number.
+                "channel %d / %d", pipeline->channel + 1, pipeline->file->get_channels()
             ).utf8_str()
         ));
     }
@@ -273,6 +276,11 @@ std::string spek_pipeline_desc(const struct spek_pipeline *pipeline)
     return desc;
 }
 
+int spek_pipeline_channels(const struct spek_pipeline *pipeline)
+{
+    return pipeline->file->get_channels();
+}
+
 double spek_pipeline_duration(const struct spek_pipeline *pipeline)
 {
     return pipeline->file->get_duration();

src/spek-pipeline.h

@@ -20,6 +20,7 @@ typedef void (*spek_pipeline_cb)(int bands, int sample, float *values, void *cb_
 struct spek_pipeline * spek_pipeline_open(
     std::unique_ptr<AudioFile> file,
     std::unique_ptr<FFTPlan> fft,
+    int channel,
     enum window_function window_function,
     int samples,
     spek_pipeline_cb cb,
@@ -30,5 +31,6 @@ void spek_pipeline_start(struct spek_pipeline *pipeline);
 void spek_pipeline_close(struct spek_pipeline *pipeline);
 
 std::string spek_pipeline_desc(const struct spek_pipeline *pipeline);
+int spek_pipeline_channels(const struct spek_pipeline *pipeline);
 double spek_pipeline_duration(const struct spek_pipeline *pipeline);
 int spek_pipeline_sample_rate(const struct spek_pipeline *pipeline);

src/spek-spectrogram.cc

@@ -47,6 +47,8 @@ SpekSpectrogram::SpekSpectrogram(wxFrame *parent) :
     audio(new Audio()), // TODO: refactor
     fft(new FFT()),
     pipeline(NULL),
+    channels(0),
+    channel(0),
     window_function(WINDOW_DEFAULT),
     duration(0.0),
     sample_rate(0),
@@ -72,6 +74,7 @@ SpekSpectrogram::~SpekSpectrogram()
 void SpekSpectrogram::open(const wxString& path)
 {
     this->path = path;
+    this->channel = 0;
     start();
     Refresh();
 }
@@ -88,6 +91,12 @@ void SpekSpectrogram::save(const wxString& path)
 void SpekSpectrogram::on_char(wxKeyEvent& evt)
 {
     switch (evt.GetKeyCode()) {
+    case 'C':
+        this->channel = (this->channel + 1) % this->channels;
+        break;
+    case 'c':
+        this->channel = (this->channel - 1 + this->channels) % this->channels;
+        break;
     case 'F':
         this->window_function = (enum window_function) ((this->window_function + 1) % WINDOW_COUNT);
         break;
@@ -367,6 +376,7 @@ void SpekSpectrogram::start()
         this->pipeline = spek_pipeline_open(
             this->audio->open(std::string(this->path.utf8_str())),
             this->fft->create(this->fft_bits),
+            this->channel,
             this->window_function,
             samples,
             pipeline_cb,
@@ -375,6 +385,7 @@ void SpekSpectrogram::start()
         spek_pipeline_start(this->pipeline);
         // TODO: extract conversion into a utility function.
         this->desc = wxString::FromUTF8(spek_pipeline_desc(this->pipeline).c_str());
+        this->channels = spek_pipeline_channels(this->pipeline);
         this->duration = spek_pipeline_duration(this->pipeline);
         this->sample_rate = spek_pipeline_sample_rate(this->pipeline);
     } else {

src/spek-spectrogram.h

@@ -35,6 +35,8 @@ private:
     std::unique_ptr<Audio> audio;
     std::unique_ptr<FFT> fft;
     spek_pipeline *pipeline;
+    int channels;
+    int channel;
     enum window_function window_function;
     wxString path;
     wxString desc;