Revert 276344 "Add callback in VideoDecoder and AudioDecoder to ..."

media/base/video_decoder.h

 // Copyright (c) 2012 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_BASE_VIDEO_DECODER_H_
 #define MEDIA_BASE_VIDEO_DECODER_H_
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "media/base/media_export.h"
 #include "media/base/pipeline_status.h"
 #include "ui/gfx/size.h"
 
 namespace media {
 
 class DecoderBuffer;
 class VideoDecoderConfig;
 class VideoFrame;
 
 class MEDIA_EXPORT VideoDecoder {
  public:
   // Status codes for decode operations on VideoDecoder.
   // TODO(rileya): Now that both AudioDecoder and VideoDecoder Status enums
   // match, break them into a decoder_status.h.
   enum Status {
     kOk,  // Everything went as planned.
     kAborted,  // Decode was aborted as a result of Reset() being called.
+    kNotEnoughData,  // Not enough data to produce a video frame.
     kDecodeError,  // Decoding error happened.
     kDecryptError  // Decrypting error happened.
   };
 
-  // Callback to return decode frames.
-  typedef base::Callback<void(const scoped_refptr<VideoFrame>&)> OutputCB;
-
-  // Callback type for Decode(). Called after the decoder has completed decoding
-  // corresponding DecoderBuffer, indicating that it's ready to accept another
-  // buffer to decode.
-  typedef base::Callback<void(Status status)> DecodeCB;
-
   VideoDecoder();
   virtual ~VideoDecoder();
 
   // Initializes a VideoDecoder with the given |config|, executing the
-  // |status_cb| upon completion. |output_cb| is called for each output frame
-  // decoded by Decode().
+  // |status_cb| upon completion.
   //
   // Note:
   // 1) The VideoDecoder will be reinitialized if it was initialized before.
   //    Upon reinitialization, all internal buffered frames will be dropped.
   // 2) This method should not be called during pending decode, reset or stop.
   // 3) No VideoDecoder calls except for Stop() should be made before
   //    |status_cb| is executed.
   virtual void Initialize(const VideoDecoderConfig& config,
                           bool low_delay,
-                          const PipelineStatusCB& status_cb,
-                          const OutputCB& output_cb) = 0;
+                          const PipelineStatusCB& status_cb) = 0;
 
   // Requests a |buffer| to be decoded. The status of the decoder and decoded
   // frame are returned via the provided callback. Some decoders may allow
   // decoding multiple buffers in parallel. Callers should call
   // GetMaxDecodeRequests() to get number of buffers that may be decoded in
   // parallel. Decoder must call |decode_cb| in the same order in which Decode()
   // is called.
   //
   // Implementations guarantee that the callback will not be called from within
   // this method and that |decode_cb| will not be blocked on the following
   // Decode() calls (i.e. |decode_cb| will be called even Decode() is never
   // called again).
   //
-  // After decoding is finished the decoder calls |output_cb| specified in
-  // Initialize() for each decoded frame. |output_cb| may be called before or
-  // after |decode_cb|.
-  //
-  // If |buffer| is an EOS buffer then the decoder must be flushed, i.e.
-  // |output_cb| must be called for each frame pending in the queue and
-  // |decode_cb| must be called after that.
+  // If the returned status is kOk:
+  // - Non-EOS (end of stream) frame contains decoded video data.
+  // - EOS frame indicates the end of the stream.
+  // Otherwise the returned frame must be NULL.
+  typedef base::Callback<void(Status,
+                              const scoped_refptr<VideoFrame>&)> DecodeCB;
   virtual void Decode(const scoped_refptr<DecoderBuffer>& buffer,
                       const DecodeCB& decode_cb) = 0;
 
-  // Resets decoder state. All pending Decode() requests will be finished or
-  // aborted before |closure| is called.
+  // Some VideoDecoders may queue up multiple VideoFrames from a single
+  // DecoderBuffer, if we have any such queued frames this will return the next
+  // one. Otherwise we return a NULL VideoFrame.
+  //
+  // TODO(xhwang): Revisit this method.
+  virtual scoped_refptr<VideoFrame> GetDecodeOutput();
+
+  // Resets decoder state, fulfilling all pending DecodeCB and dropping extra
+  // queued decoded data. After this call, the decoder is back to an initialized
+  // clean state.
   // Note: No VideoDecoder calls should be made before |closure| is executed.
   virtual void Reset(const base::Closure& closure) = 0;
 
   // Stops decoder, fires any pending callbacks and sets the decoder to an
   // uninitialized state. A VideoDecoder cannot be re-initialized after it has
   // been stopped.
   // Note that if Initialize() is pending or has finished successfully, Stop()
   // must be called before destructing the decoder.
   virtual void Stop() = 0;
 
   // Returns true if the decoder needs bitstream conversion before decoding.
   virtual bool NeedsBitstreamConversion() const;
 
   // Returns true if the decoder currently has the ability to decode and return
   // a VideoFrame. Most implementations can allocate a new VideoFrame and hence
   // this will always return true. Override and return false for decoders that
   // use a fixed set of VideoFrames for decoding.
   virtual bool CanReadWithoutStalling() const;
 
   // Returns maximum number of parallel decode requests.
   virtual int GetMaxDecodeRequests() const;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(VideoDecoder);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_VIDEO_DECODER_H_