resampler: improve reliability

Improves reliability of resampler by setting the input and output
channel counts and by forcing initialization on the first resampling.

Removes redundancy by using the sample format in AudioFormat.

Change-Id: Ie0154d5b46db6735dbc8da81fdb0e6be795a3efa

src/debug_utils.h

@@ -160,6 +160,7 @@ private:
                 output->format = AV_SAMPLE_FMT_S64;
             output->sample_rate = input->sample_rate;
             output->channel_layout = input->channel_layout;
+            output->channels = input->channels;
             resampler_->resample(input, output);
             av_frame_unref(input);
             av_frame_move_ref(frame, output);

src/media/audio/audiobuffer.h

@@ -57,6 +57,12 @@ struct AudioFormat {
         , sampleFormat(AV_SAMPLE_FMT_S16)
     {}
 
+    constexpr AudioFormat(unsigned sr, unsigned c, AVSampleFormat f)
+        : sample_rate(sr)
+        , nb_channels(c)
+        , sampleFormat(f)
+    {}
+
     inline bool operator == (const AudioFormat &b) const {
         return ( (b.sample_rate == sample_rate) &&
                  (b.nb_channels == nb_channels) &&

src/media/audio/resampler.cpp

@@ -35,6 +35,7 @@ namespace ring {
 
 Resampler::Resampler()
     : swrCtx_(swr_alloc())
+    , initialized_(false)
 {}
 
 Resampler::~Resampler()
@@ -43,29 +44,33 @@ Resampler::~Resampler()
 }
 
 void
-Resampler::reinit(const AudioFormat& in, const int inSampleFmt,
-                  const AudioFormat& out, const int outSampleFmt)
+Resampler::reinit(const AudioFormat& in, const AudioFormat& out)
 {
-    av_opt_set_int(swrCtx_, "ich", 0, 0);
+    av_opt_set_int(swrCtx_, "ich", in.nb_channels, 0);
     av_opt_set_int(swrCtx_, "icl", av_get_default_channel_layout(in.nb_channels), 0);
     av_opt_set_int(swrCtx_, "isr", in.sample_rate, 0);
-    av_opt_set_sample_fmt(swrCtx_, "isf", static_cast<AVSampleFormat>(inSampleFmt), 0);
+    av_opt_set_sample_fmt(swrCtx_, "isf", in.sampleFormat, 0);
 
-    av_opt_set_int(swrCtx_, "och", 0, 0);
+    av_opt_set_int(swrCtx_, "och", out.nb_channels, 0);
     av_opt_set_int(swrCtx_, "ocl", av_get_default_channel_layout(out.nb_channels), 0);
     av_opt_set_int(swrCtx_, "osr", out.sample_rate, 0);
-    av_opt_set_sample_fmt(swrCtx_, "osf", static_cast<AVSampleFormat>(outSampleFmt), 0);
+    av_opt_set_sample_fmt(swrCtx_, "osf", out.sampleFormat, 0);
 
     swr_init(swrCtx_);
+    initialized_ = true;
 }
 
 int
 Resampler::resample(const AVFrame* input, AVFrame* output)
 {
+    const auto inFmt = AudioFormat((unsigned)input->sample_rate, (unsigned)input->channels, (AVSampleFormat)input->format);
+    const auto outFmt = AudioFormat((unsigned)output->sample_rate, (unsigned)output->channels, (AVSampleFormat)output->format);
+    if (!initialized_)
+        reinit(inFmt, outFmt);
+
     int ret = swr_convert_frame(swrCtx_, output, input);
     if (ret & AVERROR_INPUT_CHANGED || ret & AVERROR_OUTPUT_CHANGED) {
-        reinit(AudioFormat{(unsigned)input->sample_rate, (unsigned)input->channels}, input->format,
-               AudioFormat{(unsigned)output->sample_rate, (unsigned)output->channels}, output->format);
+        reinit(inFmt, outFmt);
         return resample(input, output);
     } else if (ret < 0) {
         RING_ERR() << "Failed to resample frame";
@@ -84,6 +89,7 @@ Resampler::resample(const AudioBuffer& dataIn, AudioBuffer& dataOut)
     auto output = resampled.pointer();
     output->sample_rate = dataOut.getSampleRate();
     output->channel_layout = av_get_default_channel_layout(dataOut.channels());
+    output->channels = dataOut.channels();
     output->format = AV_SAMPLE_FMT_S16;
 
     if (resample(input, output) < 0)

src/media/audio/resampler.h

@@ -59,10 +59,10 @@ class Resampler {
          * output buffers always have the same formats, will never be called, as the first
          * initialization is done in swr_convert_frame.
          */
-        void reinit(const AudioFormat& in, const int inSampleFmt,
-                    const AudioFormat& out, const int outSampleFmt);
+        void reinit(const AudioFormat& in, const AudioFormat& out);
 
         SwrContext* swrCtx_; // incomplete type, cannot be a unique_ptr
+        bool initialized_;
 };
 
 } // namespace ring

src/media/audio/sound/audiofile.cpp

@@ -70,7 +70,8 @@ AudioFile::AudioFile(const std::string &fileName, unsigned int sampleRate) :
         throw AudioFileException("Decoder setup failed: " + fileName);
 
     auto resampler = std::make_unique<Resampler>();
-    auto buf = std::make_unique<AudioBuffer>(0, getFormat());
+    const auto& format = getFormat();
+    auto buf = std::make_unique<AudioBuffer>(0, format);
     bool done = false;
     while (!done) {
         AudioFrame input;
@@ -78,9 +79,10 @@ AudioFile::AudioFile(const std::string &fileName, unsigned int sampleRate) :
         auto resampled = output.pointer();
         switch (decoder->decode(input)) {
         case MediaDecoder::Status::FrameFinished:
-            resampled->sample_rate = getFormat().sample_rate;
-            resampled->channel_layout = av_get_default_channel_layout(getFormat().nb_channels);
-            resampled->format = AV_SAMPLE_FMT_S16;
+            resampled->sample_rate = format.sample_rate;
+            resampled->channel_layout = av_get_default_channel_layout(format.nb_channels);
+            resampled->channels = format.nb_channels;
+            resampled->format = format.sampleFormat;
             if (resampler->resample(input.pointer(), resampled) < 0)
                 throw AudioFileException("Frame could not be resampled");
             if (buf->append(output) < 0)

test/unitTest/media/audio/test_resampler.cpp

@@ -97,6 +97,7 @@ ResamplerTest::testAudioFrame()
     output->format = AV_SAMPLE_FMT_FLT;
     output->sample_rate = 48000;
     output->channel_layout = AV_CH_LAYOUT_STEREO;
+    output->channels = 2;
 
     int ret = resampler_->resample(input->pointer(), output);
     CPPUNIT_ASSERT_MESSAGE(libav_utils::getError(ret).c_str(), ret >= 0);