Avoid passing lots of zero samples when seeking.

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

src/testhls.cc

@@ -321,8 +321,6 @@ public:
 int
 mark_zexpand (WavData& wav_data, size_t zero_frames, const string& bits)
 {
-  vector<float> samples;
-
   WDInputStream in_stream (&wav_data);
 
   WavData wav_data_out ({ /* no samples */ }, wav_data.n_channels(), wav_data.sample_rate(), wav_data.bit_depth());
@@ -332,9 +330,7 @@ mark_zexpand (WavData& wav_data, size_t zero_frames, const string& bits)
   if (rc != 0)
     return rc;
 
-  samples = wav_data_out.samples();
-  samples.erase (samples.begin(), samples.begin() + zero_frames * wav_data.n_channels());
-  wav_data.set_samples (samples);
+  wav_data.set_samples (wav_data_out.samples());
 
   return 0;
 }

src/wmadd.cc

@@ -35,6 +35,7 @@
 using std::string;
 using std::vector;
 using std::complex;
+using std::min;
 using std::max;
 
 enum class FrameMod : uint8_t {
@@ -672,6 +673,7 @@ add_stream_watermark (AudioInputStream *in_stream, AudioOutputStream *out_stream
   size_t total_input_frames = 0;
   size_t total_output_frames = 0;
   size_t audio_buffer_frames = 0;
+  size_t zero_frames_out = zero_frames;
   Error err;
   if (zero_frames >= Params::frame_size)
     {
@@ -684,22 +686,9 @@ add_stream_watermark (AudioInputStream *in_stream, AudioOutputStream *out_stream
 
       frames = limiter.skip (frames);
 
-      vector<float> zblock (Params::frame_size * n_channels);
-      size_t wframes = frames;
-      while (wframes > 0)
-        {
-          if (wframes >= Params::frame_size)
-            {
-              err = out_stream->write_frames (zblock);
-              wframes -= Params::frame_size;
-            }
-          else
-            {
-              zblock.resize (wframes * n_channels);
-              err = out_stream->write_frames (zblock);
-              wframes = 0;
-            }
-        }
+      assert (frames < zero_frames_out);
+      zero_frames_out -= frames;
+
       total_output_frames += frames;
 
       zero_frames -= Params::frame_size * skip_blocks;
@@ -759,6 +748,14 @@ add_stream_watermark (AudioInputStream *in_stream, AudioOutputStream *out_stream
       if (samples.size() > max_write_frames * n_channels)
         samples.resize (max_write_frames * n_channels);
 
+      const size_t cut_frames = min (samples.size() / n_channels, zero_frames_out);
+      if (cut_frames > 0)
+        {
+          samples.erase (samples.begin(), samples.begin() + cut_frames * n_channels);
+          total_output_frames += cut_frames;
+          zero_frames_out -= cut_frames;
+        }
+
       err = out_stream->write_frames (samples);
       if (err)
         {