Add case for start=stop

Author: NicolasHug

src/torchcodec/decoders/_core/VideoDecoder.cpp

@@ -842,6 +842,8 @@ VideoDecoder::FrameBatchOutput VideoDecoder::getFramesPlayedInRange(
 torch::Tensor VideoDecoder::getFramesPlayedInRangeAudio(
     double startSeconds,
     std::optional<double> stopSecondsOptional) {
+  validateActiveStream(AVMEDIA_TYPE_AUDIO);
+
   double stopSeconds =
       stopSecondsOptional.value_or(std::numeric_limits<double>::max());
 
@@ -851,7 +853,10 @@ torch::Tensor VideoDecoder::getFramesPlayedInRangeAudio(
           ") must be less than or equal to stop seconds (" +
           std::to_string(stopSeconds) + ".");
 
-  validateActiveStream(AVMEDIA_TYPE_AUDIO);
+  if (startSeconds == stopSeconds) {
+    // For consistency with video
+    return torch::empty({0});
+  }
 
   StreamInfo& streamInfo = streamInfos_[activeStreamIndex_];
 

test/decoders/test_ops.py

@@ -723,6 +723,15 @@ def test_decode_just_one_frame_at_boundaries(self, asset, expected_shape):
         )
         assert frames.shape == expected_shape
 
+    @pytest.mark.parametrize("asset", (NASA_AUDIO, NASA_AUDIO_MP3))
+    def test_decode_start_equal_stop(self, asset):
+        decoder = create_from_file(str(asset.path), seek_mode="approximate")
+        add_audio_stream(decoder)
+        frames = get_frames_by_pts_in_range_audio(
+            decoder, start_seconds=1, stop_seconds=1
+        )
+        assert frames.shape == (0,)
+
     @pytest.mark.parametrize("asset", (NASA_AUDIO, NASA_AUDIO_MP3))
     def test_multiple_calls(self, asset):
         # Ensure that multiple calls are OK as long as we're decoding