text: // Copyright 2016 The TensorFlow Authors. All Rights Reserved.
  //
  // Licensed under the Apache License, Version 2.0 (the "License");
  // you may not use this file except in compliance with the License.
  // You may obtain a copy of the License at
  //
  //     http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing, software
  // distributed under the License is distributed on an "AS IS" BASIS,
  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  // See the License for the specific language governing permissions and
  // limitations under the License.
  // =============================================================================
  
  #include <stdlib.h>
  
  #include <cstdio>
  #include <set>
  
  #include "tensorflow/contrib/ffmpeg/ffmpeg_lib.h"
  #include "tensorflow/core/framework/op.h"
  #include "tensorflow/core/framework/op_kernel.h"
  #include "tensorflow/core/framework/shape_inference.h"
  #include "tensorflow/core/lib/io/path.h"
  #include "tensorflow/core/lib/strings/str_util.h"
  #include "tensorflow/core/lib/strings/strcat.h"
  #include "tensorflow/core/platform/env.h"
  #include "tensorflow/core/platform/logging.h"
  
  namespace tensorflow {
  namespace ffmpeg {
  
  class DecodeVideoOp : public OpKernel {
   public:
    explicit DecodeVideoOp(OpKernelConstruction* context) : OpKernel(context) {}
  
    void Compute(OpKernelContext* context) override {
      OP_REQUIRES(
          context, context->num_inputs() == 1,
          errors::InvalidArgument("DecodeVideo requires exactly 1 input."));
      const Tensor& contents_tensor = context->input(0);
  
      OP_REQUIRES(context, TensorShapeUtils::IsScalar(contents_tensor.shape()),
                  errors::InvalidArgument(
                      "contents must be a rank-0 tensor but got shape ",
                      contents_tensor.shape().DebugString()));
      const tensorflow::StringPiece contents = contents_tensor.scalar<string>()();
  
      // Write the input data to a temp file.
      string extension;
      const string temp_filename = io::GetTempFilename(extension);
      OP_REQUIRES_OK(context, WriteFile(temp_filename, contents));
      FileDeleter deleter(temp_filename);
  
      uint32 width = 0;
      uint32 height = 0;
      uint32 frames = 0;
  
      // Run FFmpeg on the data and verify results.
      std::vector<uint8> output_data;
      const Status result = ffmpeg::ReadVideoFile(temp_filename, &output_data,
                                                  &width, &height, &frames);
      if (result.code() == error::Code::NOT_FOUND) {
        OP_REQUIRES(
            context, result.ok(),
            errors::Unavailable("FFmpeg must be installed to run this op. FFmpeg "
                                "can be found at http://www.ffmpeg.org."));
      } else if (result.code() == error::UNKNOWN) {
        LOG(ERROR) << "Ffmpeg failed with error '" << result.error_message()
                   << "'. Returning empty tensor.";
        Tensor* output = nullptr;
        OP_REQUIRES_OK(context,
                       context->allocate_output(0, TensorShape({0, 0}), &output));
        return;
      } else {
        OP_REQUIRES_OK(context, result);
      }
      OP_REQUIRES(context, !output_data.empty(),
                  errors::Unknown("No output created by FFmpeg."));
      OP_REQUIRES(
          context, output_data.size() == (frames * height * width * 3),
          errors::Unknown("Output created by FFmpeg [", output_data.size(),
                          "] does not match description [", frames, ", ", height,
                          ", ", width, ", 3]"));
      Tensor* output = nullptr;
      OP_REQUIRES_OK(context,
                     context->allocate_output(
                         0, TensorShape({frames, height, width, 3}), &output));
      auto output_flat = output->flat<uint8>();
      std::copy_n(output_data.begin(), output_data.size(), &output_flat(0));
    }
  };
  
  REGISTER_KERNEL_BUILDER(Name("DecodeVideo").Device(DEVICE_CPU), DecodeVideoOp);
  
  REGISTER_OP("DecodeVideo")
      .Input("contents: string")
      .Output("output: uint8")
      .SetShapeFn([](shape_inference::InferenceContext* c) {
        c->set_output(0, c->UnknownShapeOfRank(4));
        return Status::OK();
      })
      .Doc(R"doc(
  Processes the contents of an audio file into a tensor using FFmpeg to decode
  the file.
  
  One row of the tensor is created for each channel in the audio file. Each
  channel contains audio samples starting at the beginning of the audio and
  having `1/samples_per_second` time between them. If the `channel_count` is
  different from the contents of the file, channels will be merged or created.
  
  contents: The binary audio file contents, as a string or rank-0 string
      tensor.
  )doc");
  
  }  // namespace ffmpeg
  }  // namespace tensorflow
  