Add frame refresh to VideoCaptureDevice, and buffer pool resurrection.

content/browser/renderer_host/media/video_capture_buffer_pool.h

 // Copyright (c) 2013 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 CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_BUFFER_POOL_H_
 #define CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_BUFFER_POOL_H_
 
 #include <stddef.h>
 
 #include <map>
@@ skipping 73 matching lines @@
   // all allocated buffers are in use by the producer and/or consumers.
   //
   // If successful, the reserved buffer remains reserved (and writable by the
   // producer) until ownership is transferred either to the consumer via
   // HoldForConsumers(), or back to the pool with
   // RelinquishProducerReservation().
   //
   // On occasion, this call will decide to free an old buffer to make room for a
   // new allocation at a larger size. If so, the ID of the destroyed buffer is
   // returned via |buffer_id_to_drop|.
-  int ReserveForProducer(media::VideoPixelFormat format,
+  int ReserveForProducer(const gfx::Size& dimensions,
+                         media::VideoPixelFormat format,
                          media::VideoPixelStorage storage,
-                         const gfx::Size& dimensions,
                          int* buffer_id_to_drop);
 
   // Indicate that a buffer held for the producer should be returned back to the
   // pool without passing on to the consumer. This effectively is the opposite
   // of ReserveForProducer().
   void RelinquishProducerReservation(int buffer_id);
 
   // Transfer a buffer from producer to consumer ownership.
   // |buffer_id| must be a buffer index previously returned by
   // ReserveForProducer(), and not already passed to HoldForConsumers().
   void HoldForConsumers(int buffer_id, int num_clients);
 
   // Indicate that one or more consumers are done with a particular buffer. This
   // effectively is the opposite of HoldForConsumers(). Once the consumers are
   // done, a buffer is returned to the pool for reuse.
   void RelinquishConsumerHold(int buffer_id, int num_clients);
 
+  // Attempt to reserve the same buffer that was relinquished in the last call
+  // to RelinquishProducerReservation(). If the buffer is not still being
+  // consumed, and has not yet been re-used since being consumed, and the
+  // specified |dimensions|, |format|, and |storage| agree with its last
+  // reservation, this will succeed. Otherwise, |kInvalidId| will be returned.
+  //
+  // A producer may assume the content of the buffer has been preserved and may
+  // also make modifications.
+  int ResurrectLastForProducer(const gfx::Size& dimensions,
+                               media::VideoPixelFormat format,
+                               media::VideoPixelStorage storage);
+
   // Returns a snapshot of the current number of buffers in-use divided by the
   // maximum |count_|.
   double GetBufferPoolUtilization() const;
 
  private:
   class GpuMemoryBufferTracker;
   class SharedMemTracker;
   // Generic class to keep track of the state of a given mappable resource. Each
   // Tracker carries indication of pixel format and storage type.
   class Tracker {
    public:
     static scoped_ptr<Tracker> CreateTracker(media::VideoPixelStorage storage);
 
     Tracker()
-        : pixel_count_(0), held_by_producer_(false), consumer_hold_count_(0) {}
-    virtual bool Init(media::VideoPixelFormat format,
+        : max_pixel_count_(0),
+          held_by_producer_(false),
+          consumer_hold_count_(0) {}
+    virtual bool Init(const gfx::Size& dimensions,
+                      media::VideoPixelFormat format,
                       media::VideoPixelStorage storage_type,
-                      const gfx::Size& dimensions,
                       base::Lock* lock) = 0;
     virtual ~Tracker();
 
-    size_t pixel_count() const { return pixel_count_; }
-    void set_pixel_count(size_t count) { pixel_count_ = count; }
+    const gfx::Size& dimensions() const { return dimensions_; }
+    void set_dimensions(const gfx::Size& dim) { dimensions_ = dim; }
+    size_t max_pixel_count() const { return max_pixel_count_; }
+    void set_max_pixel_count(size_t count) { max_pixel_count_ = count; }
     media::VideoPixelFormat pixel_format() const {
       return pixel_format_;
     }
     void set_pixel_format(media::VideoPixelFormat format) {
       pixel_format_ = format;
     }
     media::VideoPixelStorage storage_type() const { return storage_type_; }
     void set_storage_type(media::VideoPixelStorage storage_type) {
       storage_type_ = storage_type;
     }
     bool held_by_producer() const { return held_by_producer_; }
     void set_held_by_producer(bool value) { held_by_producer_ = value; }
     int consumer_hold_count() const { return consumer_hold_count_; }
     void set_consumer_hold_count(int value) { consumer_hold_count_ = value; }
 
     // Returns a handle to the underlying storage, be that a block of Shared
     // Memory, or a GpuMemoryBuffer.
     virtual scoped_ptr<BufferHandle> GetBufferHandle() = 0;
 
     virtual bool ShareToProcess(base::ProcessHandle process_handle,
                                 base::SharedMemoryHandle* new_handle) = 0;
     virtual bool ShareToProcess2(int plane,
                                  base::ProcessHandle process_handle,
                                  gfx::GpuMemoryBufferHandle* new_handle) = 0;
 
    private:
-    size_t pixel_count_;
+    // |dimensions_| may change as a Tracker is re-used, but |max_pixel_count_|,
+    // |pixel_format_|, and |storage_type_| are set once for the lifetime of a
+    // Tracker.
+    gfx::Size dimensions_;
+    size_t max_pixel_count_;
     media::VideoPixelFormat pixel_format_;
     media::VideoPixelStorage storage_type_;
+
     // Indicates whether this Tracker is currently referenced by the producer.
     bool held_by_producer_;
+
     // Number of consumer processes which hold this Tracker.
     int consumer_hold_count_;
   };
 
   friend class base::RefCountedThreadSafe<VideoCaptureBufferPool>;
   virtual ~VideoCaptureBufferPool();
 
-  int ReserveForProducerInternal(media::VideoPixelFormat format,
+  int ReserveForProducerInternal(const gfx::Size& dimensions,
+                                 media::VideoPixelFormat format,
                                  media::VideoPixelStorage storage,
-                                 const gfx::Size& dimensions,
                                  int* tracker_id_to_drop);
 
   Tracker* GetTracker(int buffer_id);
 
   // The max number of buffers that the pool is allowed to have at any moment.
   const int count_;
 
   // Protects everything below it.
   mutable base::Lock lock_;
 
   // The ID of the next buffer.
   int next_buffer_id_;
 
+  // The ID of the buffer last relinquished by the producer (a candidate for
+  // resurrection).
+  int last_relinquished_buffer_id_;
+
   // The buffers, indexed by the first parameter, a buffer id.
   using TrackerMap = std::map<int, Tracker*>;
   TrackerMap trackers_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(VideoCaptureBufferPool);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_BUFFER_POOL_H_