media/gpu/vp8_decoder.h

// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_GPU_VP8_DECODER_H_
#define MEDIA_GPU_VP8_DECODER_H_

#include <stddef.h>
#include <stdint.h>

#include <memory>

#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "media/filters/vp8_parser.h"
#include "media/gpu/accelerated_video_decoder.h"
#include "media/gpu/vp8_picture.h"
#include "media/gpu/vp8_reference_frame_vector.h"

namespace media {

// Clients of this class are expected to pass raw VP8 stream and are expected
// to provide an implementation of VP8Accelerator for offloading final steps
// of the decoding process.
//
// This class must be created, called and destroyed on a single thread, and
// does nothing internally on any other thread.
class MEDIA_GPU_EXPORT VP8Decoder : public AcceleratedVideoDecoder {
 public:
  class MEDIA_GPU_EXPORT VP8Accelerator {
   public:
    VP8Accelerator();
    virtual ~VP8Accelerator();

    // Create a new VP8Picture that the decoder client can use for decoding
    // and pass back to this accelerator for decoding or reference.
    // When the picture is no longer needed by decoder, it will just drop
    // its reference to it, and it may do so at any time.
    // Note that this may return nullptr if accelerator is not able to provide
    // any new pictures at given time. The decoder is expected to handle
    // this situation as normal and return from Decode() with kRanOutOfSurfaces.
    virtual scoped_refptr<VP8Picture> CreateVP8Picture() = 0;

    // Submits decode for |pic|, using |reference_frames| as references, as per
    // VP8 specification. Returns true if successful.
    virtual bool SubmitDecode(
        scoped_refptr<VP8Picture> pic,
        const Vp8ReferenceFrameVector& reference_frames) = 0;

    // Schedule output (display) of |pic|. Note that returning from this
    // method does not mean that |pic| has already been outputted (displayed),
    // but guarantees that all pictures will be outputted in the same order
    // as this method was called for them. Decoder may drop its reference
    // to |pic| after calling this method.
    // Return true if successful.
    virtual bool OutputPicture(const scoped_refptr<VP8Picture>& pic) = 0;

   private:
    DISALLOW_COPY_AND_ASSIGN(VP8Accelerator);
  };

  explicit VP8Decoder(std::unique_ptr<VP8Accelerator> accelerator);
  ~VP8Decoder() override;

  // AcceleratedVideoDecoder implementation.
  void SetStream(int32_t id,
                 const uint8_t* ptr,
                 size_t size,
                 const DecryptConfig* decrypt_config = nullptr) override;
  bool Flush() override WARN_UNUSED_RESULT;
  void Reset() override;
  DecodeResult Decode() override WARN_UNUSED_RESULT;
  gfx::Size GetPicSize() const override;
  size_t GetRequiredNumOfPictures() const override;

 private:
  bool DecodeAndOutputCurrentFrame(scoped_refptr<VP8Picture> pic);

  enum State {
    kNeedStreamMetadata,  // After initialization, need a keyframe.
    kDecoding,            // Ready to decode from any point.
    kAfterReset,          // After Reset(), need a resume point.
    kError,               // Error in decode, can't continue.
  };

  State state_;

  Vp8Parser parser_;

  std::unique_ptr<Vp8FrameHeader> curr_frame_hdr_;
  Vp8ReferenceFrameVector ref_frames_;

  // Current stream buffer id; to be assigned to pictures decoded from it.
  static constexpr int32_t kInvalidId = -1;
  int32_t stream_id_ = kInvalidId;
  int32_t last_decoded_stream_id_ = kInvalidId;
  size_t size_change_failure_counter_ = 0;

  const uint8_t* curr_frame_start_;
  size_t frame_size_;

  gfx::Size pic_size_;
  int horizontal_scale_;
  int vertical_scale_;

  const std::unique_ptr<VP8Accelerator> accelerator_;

  DISALLOW_COPY_AND_ASSIGN(VP8Decoder);
};

}  // namespace media

#endif  // MEDIA_GPU_VP8_DECODER_H_