AudioWaveformData: Adding protection from divide by zero and readers with no audio, including additional unit tests and a faster zero() function

Author: jonoomph

src/AudioWaveformer.cpp

@@ -47,10 +47,20 @@ AudioWaveformData AudioWaveformer::ExtractSamples(int channel, int num_per_secon
         int total_samples = num_per_second * (reader->info.duration + 1.0);
         int extracted_index = 0;
 
+        // Force output to zero elements for non-audio readers
+        if (!reader->info.has_audio) {
+            total_samples = 0;
+        }
+
         // Resize and clear audio buffers
         data.resize(total_samples);
         data.zero(total_samples);
 
+        // Bail out, if no samples needed
+        if (total_samples == 0 || reader->info.channels == 0) {
+            return data;
+        }
+
         // Loop through all frames
         int sample_index = 0;
         float samples_max = 0.0;

src/AudioWaveformer.h

@@ -39,10 +39,8 @@ namespace openshot {
 
         /// Zero out # of values in both datasets
         void zero(int total_samples) {
-            for (auto s = 0; s < total_samples; s++) {
-                max_samples[s] = 0.0;
-                rms_samples[s] = 0.0;
-            }
+            std::fill(max_samples.begin(), max_samples.end(), 0);
+            std::fill(rms_samples.begin(), rms_samples.end(), 0);
         }
 
         /// Scale # of values by some factor

tests/AudioWaveformer.cpp

@@ -130,3 +130,75 @@ TEST_CASE( "Normalize & scale waveform data piano.wav", "[libopenshot][audiowave
     // Clean up
     r.Close();
 }
+
+TEST_CASE( "Extract waveform from image (no audio)", "[libopenshot][audiowaveformer]" )
+{
+    // Create a reader
+    std::stringstream path;
+    path << TEST_MEDIA_PATH << "front.png";
+    FFmpegReader r(path.str());
+
+    // Create AudioWaveformer and extract a smaller "average" sample set of audio data
+    AudioWaveformer waveformer(&r);
+    AudioWaveformData waveform = waveformer.ExtractSamples(-1, 20, false);
+
+    CHECK(waveform.rms_samples.size() == 0);
+    CHECK(waveform.max_samples.size() == 0);
+
+    // Clean up
+    r.Close();
+}
+
+TEST_CASE( "AudioWaveformData struct methods", "[libopenshot][audiowaveformer]" )
+{
+    // Create a reader
+    AudioWaveformData waveform;
+
+    // Resize data to 10 elements
+    waveform.resize(10);
+    CHECK(waveform.rms_samples.size() == 10);
+    CHECK(waveform.max_samples.size() == 10);
+
+    // Set all values = 1.0
+    for (auto s = 0; s < waveform.rms_samples.size(); s++) {
+        waveform.rms_samples[s] = 1.0;
+        waveform.max_samples[s] = 1.0;
+    }
+    CHECK(waveform.rms_samples[0] == Approx(1.0f).margin(0.00001));
+    CHECK(waveform.rms_samples[9] == Approx(1.0f).margin(0.00001));
+    CHECK(waveform.max_samples[0] == Approx(1.0f).margin(0.00001));
+    CHECK(waveform.max_samples[9] == Approx(1.0f).margin(0.00001));
+
+    // Scale all values by 2
+    waveform.scale(10, 2.0);
+    CHECK(waveform.rms_samples.size() == 10);
+    CHECK(waveform.max_samples.size() == 10);
+    CHECK(waveform.rms_samples[0] == Approx(2.0f).margin(0.00001));
+    CHECK(waveform.rms_samples[9] == Approx(2.0f).margin(0.00001));
+    CHECK(waveform.max_samples[0] == Approx(2.0f).margin(0.00001));
+    CHECK(waveform.max_samples[9] == Approx(2.0f).margin(0.00001));
+
+    // Zero out all values
+    waveform.zero(10);
+    CHECK(waveform.rms_samples.size() == 10);
+    CHECK(waveform.max_samples.size() == 10);
+    CHECK(waveform.rms_samples[0] == Approx(0.0f).margin(0.00001));
+    CHECK(waveform.rms_samples[9] == Approx(0.0f).margin(0.00001));
+    CHECK(waveform.max_samples[0] == Approx(0.0f).margin(0.00001));
+    CHECK(waveform.max_samples[9] == Approx(0.0f).margin(0.00001));
+
+    // Access vectors and verify size
+    std::vector<std::vector<float>> vectors = waveform.vectors();
+    CHECK(vectors.size() == 2);
+    CHECK(vectors[0].size() == 10);
+    CHECK(vectors[0].size() == 10);
+
+    // Clear and verify internal data is empty
+    waveform.clear();
+    CHECK(waveform.rms_samples.size() == 0);
+    CHECK(waveform.max_samples.size() == 0);
+    vectors = waveform.vectors();
+    CHECK(vectors.size() == 2);
+    CHECK(vectors[0].size() == 0);
+    CHECK(vectors[0].size() == 0);
+}