Define UniqueAVBufferSrcParameters in FFMPEGCommon.h

Signed-off-by: Dmitry Rogozhkin <dmitry.v.rogozhkin@intel.com>

Author: dvrogozh

src/torchcodec/_core/FFMPEGCommon.h

@@ -13,6 +13,7 @@
 extern "C" {
 #include <libavcodec/avcodec.h>
 #include <libavfilter/avfilter.h>
+#include <libavfilter/buffersrc.h>
 #include <libavformat/avformat.h>
 #include <libavformat/avio.h>
 #include <libavutil/audio_fifo.h>
@@ -41,6 +42,15 @@ struct Deleterp {
   }
 };
 
+template <typename T, typename R, R (*Fn)(void*)>
+struct Deleterv {
+  inline void operator()(T* p) const {
+    if (p) {
+      Fn(&p);
+    }
+  }
+};
+
 template <typename T, typename R, R (*Fn)(T*)>
 struct Deleter {
   inline void operator()(T* p) const {
@@ -78,6 +88,9 @@ using UniqueAVAudioFifo = std::
     unique_ptr<AVAudioFifo, Deleter<AVAudioFifo, void, av_audio_fifo_free>>;
 using UniqueAVBufferRef =
     std::unique_ptr<AVBufferRef, Deleterp<AVBufferRef, void, av_buffer_unref>>;
+using UniqueAVBufferSrcParameters = std::unique_ptr<
+    AVBufferSrcParameters,
+    Deleterv<AVBufferSrcParameters, void, av_freep>>;
 
 // These 2 classes share the same underlying AVPacket object. They are meant to
 // be used in tandem, like so:

src/torchcodec/_core/FilterGraph.cpp

@@ -43,15 +43,7 @@ FilterGraph::FilterGraph(
   const AVFilter* buffersrc = avfilter_get_by_name("buffer");
   const AVFilter* buffersink = avfilter_get_by_name("buffersink");
 
-  auto deleter = [](AVBufferSrcParameters* p) {
-    if (p) {
-      av_freep(&p);
-    }
-  };
-  std::unique_ptr<AVBufferSrcParameters, decltype(deleter)> srcParams(
-      nullptr, deleter);
-
-  srcParams.reset(av_buffersrc_parameters_alloc());
+  UniqueAVBufferSrcParameters srcParams(av_buffersrc_parameters_alloc());
   TORCH_CHECK(srcParams, "Failed to allocate buffersrc params");
 
   srcParams->format = filtersContext.inputFormat;