From 2bc0f8cddaee61c2b5bf6a055f356b3493218427 Mon Sep 17 00:00:00 2001
From: Scott Schneider <scott.a.s@gmail.com>
Date: Fri, 13 Dec 2024 20:54:45 -0500
Subject: [PATCH] Expose constructors in C++ (#434)

---
 .../decoders/_core/VideoDecoder.cpp           | 39 ++++++++++---------
 src/torchcodec/decoders/_core/VideoDecoder.h  | 22 ++++-------
 2 files changed, 28 insertions(+), 33 deletions(-)

diff --git a/src/torchcodec/decoders/_core/VideoDecoder.cpp b/src/torchcodec/decoders/_core/VideoDecoder.cpp
index ae951b91..4c98980c 100644
--- a/src/torchcodec/decoders/_core/VideoDecoder.cpp
+++ b/src/torchcodec/decoders/_core/VideoDecoder.cpp
@@ -216,7 +216,22 @@ bool VideoDecoder::SwsContextKey::operator!=(
   return !(*this == other);
 }
 
-VideoDecoder::VideoDecoder() {}
+VideoDecoder::VideoDecoder(const std::string& videoFilePath) {
+  AVInput input = createAVFormatContextFromFilePath(videoFilePath);
+  formatContext_ = std::move(input.formatContext);
+
+  initializeDecoder();
+}
+
+VideoDecoder::VideoDecoder(const void* buffer, size_t length) {
+  TORCH_CHECK(buffer != nullptr, "Video buffer cannot be nullptr!");
+
+  AVInput input = createAVFormatContextFromBuffer(buffer, length);
+  formatContext_ = std::move(input.formatContext);
+  ioBytesContext_ = std::move(input.ioBytesContext);
+
+  initializeDecoder();
+}
 
 void VideoDecoder::initializeDecoder() {
   // Some formats don't store enough info in the header so we read/decode a few
@@ -275,28 +290,14 @@ void VideoDecoder::initializeDecoder() {
 }
 
 std::unique_ptr<VideoDecoder> VideoDecoder::createFromFilePath(
-    const std::string& videoFilePath,
-    const VideoDecoder::DecoderOptions& options) {
-  AVInput input = createAVFormatContextFromFilePath(videoFilePath);
-  std::unique_ptr<VideoDecoder> decoder(new VideoDecoder());
-  decoder->formatContext_ = std::move(input.formatContext);
-  decoder->options_ = options;
-  decoder->initializeDecoder();
-  return decoder;
+    const std::string& videoFilePath) {
+  return std::unique_ptr<VideoDecoder>(new VideoDecoder(videoFilePath));
 }
 
 std::unique_ptr<VideoDecoder> VideoDecoder::createFromBuffer(
     const void* buffer,
-    size_t length,
-    const VideoDecoder::DecoderOptions& options) {
-  TORCH_CHECK(buffer != nullptr, "Video buffer cannot be nullptr!");
-  AVInput input = createAVFormatContextFromBuffer(buffer, length);
-  std::unique_ptr<VideoDecoder> decoder(new VideoDecoder());
-  decoder->formatContext_ = std::move(input.formatContext);
-  decoder->ioBytesContext_ = std::move(input.ioBytesContext);
-  decoder->options_ = options;
-  decoder->initializeDecoder();
-  return decoder;
+    size_t length) {
+  return std::unique_ptr<VideoDecoder>(new VideoDecoder(buffer, length));
 }
 
 void VideoDecoder::initializeFilterGraph(
diff --git a/src/torchcodec/decoders/_core/VideoDecoder.h b/src/torchcodec/decoders/_core/VideoDecoder.h
index 1da745b3..fcd1b17c 100644
--- a/src/torchcodec/decoders/_core/VideoDecoder.h
+++ b/src/torchcodec/decoders/_core/VideoDecoder.h
@@ -46,27 +46,23 @@ class VideoDecoder {
  public:
   ~VideoDecoder();
 
-  struct DecoderOptions {
-    DecoderOptions() {}
-    // TODO: Add options for the entire decoder here, or remove if not needed.
-  };
-
   // --------------------------------------------------------------------------
   // CONSTRUCTION API
   // --------------------------------------------------------------------------
 
-  // Creates a VideoDecoder with the given options for the video in file
-  // `videoFilePath`. If it fails, returns an error status.
-  static std::unique_ptr<VideoDecoder> createFromFilePath(
-      const std::string& videoFilePath,
-      const DecoderOptions& options = DecoderOptions());
+  // Creates a VideoDecoder from the video at videoFilePath.
+  explicit VideoDecoder(const std::string& videoFilePath);
 
   // Creates a VideoDecoder from a given buffer. Note that the buffer is not
   // owned by the VideoDecoder.
+  explicit VideoDecoder(const void* buffer, size_t length);
+
+  static std::unique_ptr<VideoDecoder> createFromFilePath(
+      const std::string& videoFilePath);
+
   static std::unique_ptr<VideoDecoder> createFromBuffer(
       const void* buffer,
-      size_t length,
-      const DecoderOptions& options = DecoderOptions());
+      size_t length);
 
   // --------------------------------------------------------------------------
   // VIDEO METADATA QUERY API
@@ -349,7 +345,6 @@ class VideoDecoder {
     SwsContextKey swsContextKey;
     UniqueSwsContext swsContext;
   };
-  VideoDecoder();
   // Returns the key frame index of the presentation timestamp using FFMPEG's
   // index. Note that this index may be truncated for some files.
   int getKeyFrameIndexForPtsUsingEncoderIndex(AVStream* stream, int64_t pts)
@@ -409,7 +404,6 @@ class VideoDecoder {
   DecodedOutput getNextFrameOutputNoDemuxInternal(
       std::optional<torch::Tensor> preAllocatedOutputTensor = std::nullopt);
 
-  DecoderOptions options_;
   ContainerMetadata containerMetadata_;
   UniqueAVFormatContext formatContext_;
   std::map<int, StreamInfo> streams_;