Refactor FFmpegVideoDecoder to try and generalize code common to all video decoders.

media/filters/video_decode_engine.h

+// Copyright (c) 2009 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_FILTERS_VIDEO_DECODE_ENGINE_H_
+#define MEDIA_FILTERS_VIDEO_DECODE_ENGINE_H_
+
+// FFmpeg types.
+//
+// TODO(ajwong): Try to cut the dependency on the FFmpeg types.
+struct AVFrame;
+struct AVStream;
+
+class Task;
+
+namespace media {
+
+class Buffer;
+
+class VideoDecodeEngine {
+ public:
+  enum State {
+    kCreated,
+    kNormal,
+    kError,
+  };
+
+  VideoDecodeEngine() {}
+  virtual ~VideoDecodeEngine() {}
+
+  // Initialized the engine.  On successful Initialization, state() should
+  // return kNormal.
+  virtual void Initialize(AVStream* stream, Task* done_cb) = 0;
+
+  // Decodes one frame of video with the given buffer.  Returns false if there
+  // was a decode error, or a zero-byte frame was produced.
+  //
+  // TODO(ajwong): Should this function just allocate a new yuv_frame and return
+  // it via a "GetNextFrame()" method or similar?
+  virtual void DecodeFrame(const Buffer& buffer, AVFrame* yuv_frame,
+                           bool* got_result, Task* done_cb) = 0;
+
+  // Flushes the decode engine of any buffered input packets.
+  virtual void Flush(Task* done_cb) = 0;
+
+  // Returns the VideoSurface::Format of the resulting |yuv_frame| from
+  // DecodeFrame().
+  virtual VideoSurface::Format GetSurfaceFormat() const = 0;
+
+  // Returns the current state of the decode engine.
+  virtual State state() const  = 0;
+
+};
+
+}  // namespace media
+
+#endif  // MEDIA_FILTERS_VIDEO_DECODE_ENGINE_H_