Move filter graph to stand alone class (#831)

Co-authored-by: Dmitry Rogozhkin <dmitry.v.rogozhkin@gmail.com>
Co-authored-by: Nicolas Hug <nicolashug@meta.com>

Author: 3 people

src/torchcodec/_core/CMakeLists.txt

@@ -88,6 +88,7 @@ function(make_torchcodec_libraries
         AVIOContextHolder.cpp
         AVIOTensorContext.cpp
         FFMPEGCommon.cpp
+        FilterGraph.cpp
         Frame.cpp
         DeviceInterface.cpp
         CpuDeviceInterface.cpp

src/torchcodec/_core/CpuDeviceInterface.cpp

@@ -6,11 +6,6 @@
 
 #include "src/torchcodec/_core/CpuDeviceInterface.h"
 
-extern "C" {
-#include <libavfilter/buffersink.h>
-#include <libavfilter/buffersrc.h>
-}
-
 namespace facebook::torchcodec {
 namespace {
 
@@ -20,17 +15,15 @@ static bool g_cpu = registerDeviceInterface(
 
 } // namespace
 
-bool CpuDeviceInterface::DecodedFrameContext::operator==(
-    const CpuDeviceInterface::DecodedFrameContext& other) {
-  return decodedWidth == other.decodedWidth &&
-      decodedHeight == other.decodedHeight &&
-      decodedFormat == other.decodedFormat &&
-      expectedWidth == other.expectedWidth &&
-      expectedHeight == other.expectedHeight;
+bool CpuDeviceInterface::SwsFrameContext::operator==(
+    const CpuDeviceInterface::SwsFrameContext& other) const {
+  return inputWidth == other.inputWidth && inputHeight == other.inputHeight &&
+      inputFormat == other.inputFormat && outputWidth == other.outputWidth &&
+      outputHeight == other.outputHeight;
 }
 
-bool CpuDeviceInterface::DecodedFrameContext::operator!=(
-    const CpuDeviceInterface::DecodedFrameContext& other) {
+bool CpuDeviceInterface::SwsFrameContext::operator!=(
+    const CpuDeviceInterface::SwsFrameContext& other) const {
   return !(*this == other);
 }
 
@@ -75,22 +68,8 @@ void CpuDeviceInterface::convertAVFrameToFrameOutput(
   }
 
   torch::Tensor outputTensor;
-  // We need to compare the current frame context with our previous frame
-  // context. If they are different, then we need to re-create our colorspace
-  // conversion objects. We create our colorspace conversion objects late so
-  // that we don't have to depend on the unreliable metadata in the header.
-  // And we sometimes re-create them because it's possible for frame
-  // resolution to change mid-stream. Finally, we want to reuse the colorspace
-  // conversion objects as much as possible for performance reasons.
   enum AVPixelFormat frameFormat =
       static_cast<enum AVPixelFormat>(avFrame->format);
-  auto frameContext = DecodedFrameContext{
-      avFrame->width,
-      avFrame->height,
-      frameFormat,
-      avFrame->sample_aspect_ratio,
-      expectedOutputWidth,
-      expectedOutputHeight};
 
   // By default, we want to use swscale for color conversion because it is
   // faster. However, it has width requirements, so we may need to fall back
@@ -111,12 +90,27 @@ void CpuDeviceInterface::convertAVFrameToFrameOutput(
       videoStreamOptions.colorConversionLibrary.value_or(defaultLibrary);
 
   if (colorConversionLibrary == ColorConversionLibrary::SWSCALE) {
+    // We need to compare the current frame context with our previous frame
+    // context. If they are different, then we need to re-create our colorspace
+    // conversion objects. We create our colorspace conversion objects late so
+    // that we don't have to depend on the unreliable metadata in the header.
+    // And we sometimes re-create them because it's possible for frame
+    // resolution to change mid-stream. Finally, we want to reuse the colorspace
+    // conversion objects as much as possible for performance reasons.
+    SwsFrameContext swsFrameContext;
+
+    swsFrameContext.inputWidth = avFrame->width;
+    swsFrameContext.inputHeight = avFrame->height;
+    swsFrameContext.inputFormat = frameFormat;
+    swsFrameContext.outputWidth = expectedOutputWidth;
+    swsFrameContext.outputHeight = expectedOutputHeight;
+
     outputTensor = preAllocatedOutputTensor.value_or(allocateEmptyHWCTensor(
         expectedOutputHeight, expectedOutputWidth, torch::kCPU));
 
-    if (!swsContext_ || prevFrameContext_ != frameContext) {
-      createSwsContext(frameContext, avFrame->colorspace);
-      prevFrameContext_ = frameContext;
+    if (!swsContext_ || prevSwsFrameContext_ != swsFrameContext) {
+      createSwsContext(swsFrameContext, avFrame->colorspace);
+      prevSwsFrameContext_ = swsFrameContext;
     }
     int resultHeight =
         convertAVFrameToTensorUsingSwsScale(avFrame, outputTensor);
@@ -132,9 +126,29 @@ void CpuDeviceInterface::convertAVFrameToFrameOutput(
 
     frameOutput.data = outputTensor;
   } else if (colorConversionLibrary == ColorConversionLibrary::FILTERGRAPH) {
-    if (!filterGraphContext_.filterGraph || prevFrameContext_ != frameContext) {
-      createFilterGraph(frameContext, videoStreamOptions, timeBase);
-      prevFrameContext_ = frameContext;
+    // See comment above in swscale branch about the filterGraphContext_
+    // creation. creation
+    FiltersContext filtersContext;
+
+    filtersContext.inputWidth = avFrame->width;
+    filtersContext.inputHeight = avFrame->height;
+    filtersContext.inputFormat = frameFormat;
+    filtersContext.inputAspectRatio = avFrame->sample_aspect_ratio;
+    filtersContext.outputWidth = expectedOutputWidth;
+    filtersContext.outputHeight = expectedOutputHeight;
+    filtersContext.outputFormat = AV_PIX_FMT_RGB24;
+    filtersContext.timeBase = timeBase;
+
+    std::stringstream filters;
+    filters << "scale=" << expectedOutputWidth << ":" << expectedOutputHeight;
+    filters << ":sws_flags=bilinear";
+
+    filtersContext.filtergraphStr = filters.str();
+
+    if (!filterGraphContext_ || prevFiltersContext_ != filtersContext) {
+      filterGraphContext_ =
+          std::make_unique<FilterGraph>(filtersContext, videoStreamOptions);
+      prevFiltersContext_ = std::move(filtersContext);
     }
     outputTensor = convertAVFrameToTensorUsingFilterGraph(avFrame);
 
@@ -187,14 +201,8 @@ int CpuDeviceInterface::convertAVFrameToTensorUsingSwsScale(
 
 torch::Tensor CpuDeviceInterface::convertAVFrameToTensorUsingFilterGraph(
     const UniqueAVFrame& avFrame) {
-  int status = av_buffersrc_write_frame(
-      filterGraphContext_.sourceContext, avFrame.get());
-  TORCH_CHECK(
-      status >= AVSUCCESS, "Failed to add frame to buffer source context");
+  UniqueAVFrame filteredAVFrame = filterGraphContext_->convert(avFrame);
 
-  UniqueAVFrame filteredAVFrame(av_frame_alloc());
-  status = av_buffersink_get_frame(
-      filterGraphContext_.sinkContext, filteredAVFrame.get());
   TORCH_CHECK_EQ(filteredAVFrame->format, AV_PIX_FMT_RGB24);
 
   auto frameDims = getHeightAndWidthFromResizedAVFrame(*filteredAVFrame.get());
@@ -210,117 +218,15 @@ torch::Tensor CpuDeviceInterface::convertAVFrameToTensorUsingFilterGraph(
       filteredAVFramePtr->data[0], shape, strides, deleter, {torch::kUInt8});
 }
 
-void CpuDeviceInterface::createFilterGraph(
-    const DecodedFrameContext& frameContext,
-    const VideoStreamOptions& videoStreamOptions,
-    const AVRational& timeBase) {
-  filterGraphContext_.filterGraph.reset(avfilter_graph_alloc());
-  TORCH_CHECK(filterGraphContext_.filterGraph.get() != nullptr);
-
-  if (videoStreamOptions.ffmpegThreadCount.has_value()) {
-    filterGraphContext_.filterGraph->nb_threads =
-        videoStreamOptions.ffmpegThreadCount.value();
-  }
-
-  const AVFilter* buffersrc = avfilter_get_by_name("buffer");
-  const AVFilter* buffersink = avfilter_get_by_name("buffersink");
-
-  std::stringstream filterArgs;
-  filterArgs << "video_size=" << frameContext.decodedWidth << "x"
-             << frameContext.decodedHeight;
-  filterArgs << ":pix_fmt=" << frameContext.decodedFormat;
-  filterArgs << ":time_base=" << timeBase.num << "/" << timeBase.den;
-  filterArgs << ":pixel_aspect=" << frameContext.decodedAspectRatio.num << "/"
-             << frameContext.decodedAspectRatio.den;
-
-  int status = avfilter_graph_create_filter(
-      &filterGraphContext_.sourceContext,
-      buffersrc,
-      "in",
-      filterArgs.str().c_str(),
-      nullptr,
-      filterGraphContext_.filterGraph.get());
-  TORCH_CHECK(
-      status >= 0,
-      "Failed to create filter graph: ",
-      filterArgs.str(),
-      ": ",
-      getFFMPEGErrorStringFromErrorCode(status));
-
-  status = avfilter_graph_create_filter(
-      &filterGraphContext_.sinkContext,
-      buffersink,
-      "out",
-      nullptr,
-      nullptr,
-      filterGraphContext_.filterGraph.get());
-  TORCH_CHECK(
-      status >= 0,
-      "Failed to create filter graph: ",
-      getFFMPEGErrorStringFromErrorCode(status));
-
-  enum AVPixelFormat pix_fmts[] = {AV_PIX_FMT_RGB24, AV_PIX_FMT_NONE};
-
-  status = av_opt_set_int_list(
-      filterGraphContext_.sinkContext,
-      "pix_fmts",
-      pix_fmts,
-      AV_PIX_FMT_NONE,
-      AV_OPT_SEARCH_CHILDREN);
-  TORCH_CHECK(
-      status >= 0,
-      "Failed to set output pixel formats: ",
-      getFFMPEGErrorStringFromErrorCode(status));
-
-  UniqueAVFilterInOut outputs(avfilter_inout_alloc());
-  UniqueAVFilterInOut inputs(avfilter_inout_alloc());
-
-  outputs->name = av_strdup("in");
-  outputs->filter_ctx = filterGraphContext_.sourceContext;
-  outputs->pad_idx = 0;
-  outputs->next = nullptr;
-  inputs->name = av_strdup("out");
-  inputs->filter_ctx = filterGraphContext_.sinkContext;
-  inputs->pad_idx = 0;
-  inputs->next = nullptr;
-
-  std::stringstream description;
-  description << "scale=" << frameContext.expectedWidth << ":"
-              << frameContext.expectedHeight;
-  description << ":sws_flags=bilinear";
-
-  AVFilterInOut* outputsTmp = outputs.release();
-  AVFilterInOut* inputsTmp = inputs.release();
-  status = avfilter_graph_parse_ptr(
-      filterGraphContext_.filterGraph.get(),
-      description.str().c_str(),
-      &inputsTmp,
-      &outputsTmp,
-      nullptr);
-  outputs.reset(outputsTmp);
-  inputs.reset(inputsTmp);
-  TORCH_CHECK(
-      status >= 0,
-      "Failed to parse filter description: ",
-      getFFMPEGErrorStringFromErrorCode(status));
-
-  status =
-      avfilter_graph_config(filterGraphContext_.filterGraph.get(), nullptr);
-  TORCH_CHECK(
-      status >= 0,
-      "Failed to configure filter graph: ",
-      getFFMPEGErrorStringFromErrorCode(status));
-}
-
 void CpuDeviceInterface::createSwsContext(
-    const DecodedFrameContext& frameContext,
+    const SwsFrameContext& swsFrameContext,
     const enum AVColorSpace colorspace) {
   SwsContext* swsContext = sws_getContext(
-      frameContext.decodedWidth,
-      frameContext.decodedHeight,
-      frameContext.decodedFormat,
-      frameContext.expectedWidth,
-      frameContext.expectedHeight,
+      swsFrameContext.inputWidth,
+      swsFrameContext.inputHeight,
+      swsFrameContext.inputFormat,
+      swsFrameContext.outputWidth,
+      swsFrameContext.outputHeight,
       AV_PIX_FMT_RGB24,
       SWS_BILINEAR,
       nullptr,

src/torchcodec/_core/CpuDeviceInterface.h

@@ -8,6 +8,7 @@
 
 #include "src/torchcodec/_core/DeviceInterface.h"
 #include "src/torchcodec/_core/FFMPEGCommon.h"
+#include "src/torchcodec/_core/FilterGraph.h"
 
 namespace facebook::torchcodec {
 
@@ -41,40 +42,29 @@ class CpuDeviceInterface : public DeviceInterface {
   torch::Tensor convertAVFrameToTensorUsingFilterGraph(
       const UniqueAVFrame& avFrame);
 
-  struct FilterGraphContext {
-    UniqueAVFilterGraph filterGraph;
-    AVFilterContext* sourceContext = nullptr;
-    AVFilterContext* sinkContext = nullptr;
-  };
-
-  struct DecodedFrameContext {
-    int decodedWidth;
-    int decodedHeight;
-    AVPixelFormat decodedFormat;
-    AVRational decodedAspectRatio;
-    int expectedWidth;
-    int expectedHeight;
-    bool operator==(const DecodedFrameContext&);
-    bool operator!=(const DecodedFrameContext&);
+  struct SwsFrameContext {
+    int inputWidth;
+    int inputHeight;
+    AVPixelFormat inputFormat;
+    int outputWidth;
+    int outputHeight;
+    bool operator==(const SwsFrameContext&) const;
+    bool operator!=(const SwsFrameContext&) const;
   };
 
   void createSwsContext(
-      const DecodedFrameContext& frameContext,
+      const SwsFrameContext& swsFrameContext,
       const enum AVColorSpace colorspace);
 
-  void createFilterGraph(
-      const DecodedFrameContext& frameContext,
-      const VideoStreamOptions& videoStreamOptions,
-      const AVRational& timeBase);
-
   // color-conversion fields. Only one of FilterGraphContext and
   // UniqueSwsContext should be non-null.
-  FilterGraphContext filterGraphContext_;
+  std::unique_ptr<FilterGraph> filterGraphContext_;
   UniqueSwsContext swsContext_;
 
   // Used to know whether a new FilterGraphContext or UniqueSwsContext should
   // be created before decoding a new frame.
-  DecodedFrameContext prevFrameContext_;
+  SwsFrameContext prevSwsFrameContext_;
+  FiltersContext prevFiltersContext_;
 };
 
 } // namespace facebook::torchcodec

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: