Remove parameter, just sort if not already sorted

Author: NicolasHug

src/torchcodec/decoders/_core/VideoDecoder.cpp

@@ -1030,8 +1030,7 @@ VideoDecoder::DecodedOutput VideoDecoder::getFrameAtIndex(
 
 VideoDecoder::BatchDecodedOutput VideoDecoder::getFramesAtIndices(
     int streamIndex,
-    const std::vector<int64_t>& frameIndices,
-    const bool sortIndices) {
+    const std::vector<int64_t>& frameIndices) {
   validateUserProvidedStreamIndex(streamIndex);
   validateScannedAllStreams("getFramesAtIndices");
 
@@ -1040,12 +1039,15 @@ VideoDecoder::BatchDecodedOutput VideoDecoder::getFramesAtIndices(
   const auto& options = stream.options;
   BatchDecodedOutput output(frameIndices.size(), options, streamMetadata);
 
-  // if frameIndices is [13, 10, 12, 11]
-  // when sorted, it's  [10, 11, 12, 13] <-- this is the sorted order we want
-  //                                         to use to decode the frames
-  // and argsort is     [ 1,  3,  2,  0]
+  auto indicesAreSorted =
+      std::is_sorted(frameIndices.begin(), frameIndices.end());
+
   std::vector<size_t> argsort;
-  if (sortIndices) {
+  if (!indicesAreSorted) {
+    // if frameIndices is [13, 10, 12, 11]
+    // when sorted, it's  [10, 11, 12, 13] <-- this is the sorted order we want
+    //                                         to use to decode the frames
+    // and argsort is     [ 1,  3,  2,  0]
     argsort.resize(frameIndices.size());
     for (size_t i = 0; i < argsort.size(); ++i) {
       argsort[i] = i;
@@ -1058,15 +1060,15 @@ VideoDecoder::BatchDecodedOutput VideoDecoder::getFramesAtIndices(
 
   auto previousIndexInVideo = -1;
   for (auto f = 0; f < frameIndices.size(); ++f) {
-    auto indexInOutput = sortIndices ? argsort[f] : f;
+    auto indexInOutput = indicesAreSorted ? f : argsort[f];
     auto indexInVideo = frameIndices[indexInOutput];
     if (indexInVideo < 0 || indexInVideo >= stream.allFrames.size()) {
       throw std::runtime_error(
           "Invalid frame index=" + std::to_string(indexInVideo));
     }
     if ((f > 0) && (indexInVideo == previousIndexInVideo)) {
       // Avoid decoding the same frame twice
-      auto previousIndexInOutput = sortIndices ? argsort[f - 1] : f - 1;
+      auto previousIndexInOutput = indicesAreSorted ? f - 1 : argsort[f - 1];
       output.frames[indexInOutput].copy_(output.frames[previousIndexInOutput]);
       output.ptsSeconds[indexInOutput] =
           output.ptsSeconds[previousIndexInOutput];

src/torchcodec/decoders/_core/VideoDecoder.h

@@ -241,8 +241,7 @@ class VideoDecoder {
   // Tensor.
   BatchDecodedOutput getFramesAtIndices(
       int streamIndex,
-      const std::vector<int64_t>& frameIndices,
-      const bool sortIndices = false);
+      const std::vector<int64_t>& frameIndices);
   // Returns frames within a given range for a given stream as a single stacked
   // Tensor. The range is defined by [start, stop). The values retrieved from
   // the range are:

src/torchcodec/decoders/_core/VideoDecoderOps.cpp

@@ -40,7 +40,7 @@ TORCH_LIBRARY(torchcodec_ns, m) {
   m.def(
       "get_frame_at_index(Tensor(a!) decoder, *, int stream_index, int frame_index) -> (Tensor, Tensor, Tensor)");
   m.def(
-      "get_frames_at_indices(Tensor(a!) decoder, *, int stream_index, int[] frame_indices, bool sort_indices=False) -> (Tensor, Tensor, Tensor)");
+      "get_frames_at_indices(Tensor(a!) decoder, *, int stream_index, int[] frame_indices) -> (Tensor, Tensor, Tensor)");
   m.def(
       "get_frames_in_range(Tensor(a!) decoder, *, int stream_index, int start, int stop, int? step=None) -> (Tensor, Tensor, Tensor)");
   m.def(
@@ -221,13 +221,11 @@ OpsDecodedOutput get_frame_at_index(
 OpsBatchDecodedOutput get_frames_at_indices(
     at::Tensor& decoder,
     int64_t stream_index,
-    at::IntArrayRef frame_indices,
-    bool sort_indices) {
+    at::IntArrayRef frame_indices) {
   auto videoDecoder = unwrapTensorToGetDecoder(decoder);
   std::vector<int64_t> frameIndicesVec(
       frame_indices.begin(), frame_indices.end());
-  auto result = videoDecoder->getFramesAtIndices(
-      stream_index, frameIndicesVec, sort_indices);
+  auto result = videoDecoder->getFramesAtIndices(stream_index, frameIndicesVec);
   return makeOpsBatchDecodedOutput(result);
 }
 

src/torchcodec/decoders/_core/VideoDecoderOps.h

@@ -90,8 +90,7 @@ OpsDecodedOutput get_next_frame(at::Tensor& decoder);
 OpsBatchDecodedOutput get_frames_at_indices(
     at::Tensor& decoder,
     int64_t stream_index,
-    at::IntArrayRef frame_indices,
-    bool sort_indices = false);
+    at::IntArrayRef frame_indices);
 
 // Return the frames inside a range as a single stacked Tensor. The range is
 // defined as [start, stop).

src/torchcodec/decoders/_core/video_decoder_ops.py

@@ -190,7 +190,6 @@ def get_frames_at_indices_abstract(
     *,
     stream_index: int,
     frame_indices: List[int],
-    sort_indices: bool = False,
 ) -> Tuple[torch.Tensor, torch.Tensor, torch.Tensor]:
     image_size = [get_ctx().new_dynamic_size() for _ in range(4)]
     return (

test/decoders/test_video_decoder_ops.py

@@ -124,8 +124,7 @@ def test_get_frames_at_indices(self):
         assert_tensor_equal(frames0and180[0], reference_frame0)
         assert_tensor_equal(frames0and180[1], reference_frame180)
 
-    @pytest.mark.parametrize("sort_indices", (False, True))
-    def test_get_frames_at_indices_with_sort(self, sort_indices):
+    def test_get_frames_at_indices_unsorted_indices(self):
         decoder = create_from_file(str(NASA_VIDEO.path))
         _add_video_stream(decoder)
         scan_all_streams_to_update_metadata(decoder)
@@ -144,7 +143,6 @@ def test_get_frames_at_indices_with_sort(self, sort_indices):
             decoder,
             stream_index=stream_index,
             frame_indices=frame_indices,
-            sort_indices=sort_indices,
         )
         for frame, expected_frame in zip(frames, expected_frames):
             assert_tensor_equal(frame, expected_frame)