media/cast/sender/vp8_encoder.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef MEDIA_CAST_SENDER_CODECS_VP8_VP8_ENCODER_H_
   6 #define MEDIA_CAST_SENDER_CODECS_VP8_VP8_ENCODER_H_
   7
   8 #include "base/basictypes.h"
   9 #include "base/memory/scoped_ptr.h"
  10 #include "base/threading/thread_checker.h"
  11 #include "media/cast/cast_config.h"
  12 #include "media/cast/sender/software_video_encoder.h"
  13 #include "third_party/libvpx/source/libvpx/vpx/vpx_encoder.h"
  14 #include "ui/gfx/geometry/size.h"
  15
  16 namespace media {
  17 class VideoFrame;
  18 }
  19
  20 namespace media {
  21 namespace cast {
  22
  23 class Vp8Encoder : public SoftwareVideoEncoder {
  24  public:
  25   explicit Vp8Encoder(const VideoSenderConfig& video_config);
  26
  27   ~Vp8Encoder() final;
  28
  29   // SoftwareVideoEncoder implementations.
  30   void Initialize() final;
  31   void Encode(const scoped_refptr<media::VideoFrame>& video_frame,
  32               const base::TimeTicks& reference_time,
  33               SenderEncodedFrame* encoded_frame) final;
  34   void UpdateRates(uint32 new_bitrate) final;
  35   void GenerateKeyFrame() final;
  36   void LatestFrameIdToReference(uint32 frame_id) final;
  37
  38  private:
  39   enum { kNumberOfVp8VideoBuffers = 3 };
  40
  41   enum Vp8Buffers {
  42     kAltRefBuffer = 0,
  43     kGoldenBuffer = 1,
  44     kLastBuffer = 2,
  45     kNoBuffer = 3  // Note: must be last.
  46   };
  47
  48   enum Vp8BufferState {
  49     kBufferStartState,
  50     kBufferSent,
  51     kBufferAcked
  52   };
  53
  54   struct BufferState {
  55     uint32 frame_id;
  56     Vp8BufferState state;
  57   };
  58
  59   bool is_initialized() const {
  60     // ConfigureForNewFrameSize() sets the timebase denominator value to
  61     // non-zero if the encoder is successfully initialized, and it is zero
  62     // otherwise.
  63     return config_.g_timebase.den != 0;
  64   }
  65
  66   // If the |encoder_| is live, attempt reconfiguration to allow it to encode
  67   // frames at a new |frame_size|.  Otherwise, tear it down and re-create a new
  68   // |encoder_| instance.
  69   void ConfigureForNewFrameSize(const gfx::Size& frame_size);
  70
  71   // Calculate which next Vp8 buffers to update with the next frame.
  72   Vp8Buffers GetNextBufferToUpdate();
  73
  74   // Get encoder flags for our referenced encoder buffers.
  75   // Return which previous frame to reference.
  76   uint32 GetCodecReferenceFlags(vpx_codec_flags_t* flags);
  77
  78   // Get encoder flags for our encoder buffers to update with next frame.
  79   void GetCodecUpdateFlags(Vp8Buffers buffer_to_update,
  80                            vpx_codec_flags_t* flags);
  81
  82   const VideoSenderConfig cast_config_;
  83   const bool use_multiple_video_buffers_;
  84
  85   // VP8 internal objects.  These are valid for use only while is_initialized()
  86   // returns true.
  87   vpx_codec_enc_cfg_t config_;
  88   vpx_codec_ctx_t encoder_;
  89
  90   // Set to true to request the next frame emitted by Vp8Encoder be a key frame.
  91   bool key_frame_requested_;
  92
  93   // Saves the current bitrate setting, for when the |encoder_| is reconfigured
  94   // for different frame sizes.
  95   int bitrate_kbit_;
  96
  97   // The |VideoFrame::timestamp()| of the last encoded frame.  This is used to
  98   // predict the duration of the next frame.
  99   base::TimeDelta last_frame_timestamp_;
 100
 101   // The last encoded frame's ID.
 102   uint32 last_encoded_frame_id_;
 103
 104   // Used to track which buffers are old enough to be re-used.
 105   uint32 last_acked_frame_id_;
 106
 107   // Used by GetNextBufferToUpdate() to track how many consecutive times the
 108   // newest buffer had to be overwritten.
 109   int undroppable_frames_;
 110
 111   // Tracks the lifecycle and dependency state of each of the three buffers.
 112   BufferState buffer_state_[kNumberOfVp8VideoBuffers];
 113
 114   // This is bound to the thread where Initialize() is called.
 115   base::ThreadChecker thread_checker_;
 116
 117   DISALLOW_COPY_AND_ASSIGN(Vp8Encoder);
 118 };
 119
 120 }  // namespace cast
 121 }  // namespace media
 122
 123 #endif  // MEDIA_CAST_SENDER_CODECS_VP8_VP8_ENCODER_H_