media/base/video_decoder.h

   1 // Copyright (c) 2012 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_BASE_VIDEO_DECODER_H_
   6 #define MEDIA_BASE_VIDEO_DECODER_H_
   7
   8 #include "base/callback.h"
   9 #include "base/memory/ref_counted.h"
  10 #include "media/base/media_export.h"
  11 #include "media/base/pipeline_status.h"
  12 #include "ui/gfx/size.h"
  13
  14 namespace media {
  15
  16 class DecoderBuffer;
  17 class VideoDecoderConfig;
  18 class VideoFrame;
  19
  20 class MEDIA_EXPORT VideoDecoder {
  21  public:
  22   // Status codes for decode operations on VideoDecoder.
  23   // TODO(rileya): Now that both AudioDecoder and VideoDecoder Status enums
  24   // match, break them into a decoder_status.h.
  25   enum Status {
  26     kOk,  // Everything went as planned.
  27     kAborted,  // Decode was aborted as a result of Reset() being called.
  28     kDecodeError,  // Decoding error happened.
  29     kDecryptError  // Decrypting error happened.
  30   };
  31
  32   // Callback for VideoDecoder to return a decoded frame whenever it becomes
  33   // available. Only non-EOS frames should be returned via this callback.
  34   typedef base::Callback<void(const scoped_refptr<VideoFrame>&)> OutputCB;
  35
  36   // Callback type for Decode(). Called after the decoder has completed decoding
  37   // corresponding DecoderBuffer, indicating that it's ready to accept another
  38   // buffer to decode.
  39   typedef base::Callback<void(Status status)> DecodeCB;
  40
  41   VideoDecoder();
  42
  43   // Fires any pending callbacks, stops and destroys the decoder.
  44   // Note: Since this is a destructor, |this| will be destroyed after this call.
  45   // Make sure the callbacks fired from this call doesn't post any task that
  46   // depends on |this|.
  47   virtual ~VideoDecoder();
  48
  49   // Initializes a VideoDecoder with the given |config|, executing the
  50   // |status_cb| upon completion. |output_cb| is called for each output frame
  51   // decoded by Decode().
  52   //
  53   // Note:
  54   // 1) The VideoDecoder will be reinitialized if it was initialized before.
  55   //    Upon reinitialization, all internal buffered frames will be dropped.
  56   // 2) This method should not be called during pending decode or reset.
  57   // 3) No VideoDecoder calls should be made before |status_cb| is executed.
  58   virtual void Initialize(const VideoDecoderConfig& config,
  59                           bool low_delay,
  60                           const PipelineStatusCB& status_cb,
  61                           const OutputCB& output_cb) = 0;
  62
  63   // Requests a |buffer| to be decoded. The status of the decoder and decoded
  64   // frame are returned via the provided callback. Some decoders may allow
  65   // decoding multiple buffers in parallel. Callers should call
  66   // GetMaxDecodeRequests() to get number of buffers that may be decoded in
  67   // parallel. Decoder must call |decode_cb| in the same order in which Decode()
  68   // is called.
  69   //
  70   // Implementations guarantee that the callback will not be called from within
  71   // this method and that |decode_cb| will not be blocked on the following
  72   // Decode() calls (i.e. |decode_cb| will be called even Decode() is never
  73   // called again).
  74   //
  75   // After decoding is finished the decoder calls |output_cb| specified in
  76   // Initialize() for each decoded frame. |output_cb| may be called before or
  77   // after |decode_cb|.
  78   //
  79   // If |buffer| is an EOS buffer then the decoder must be flushed, i.e.
  80   // |output_cb| must be called for each frame pending in the queue and
  81   // |decode_cb| must be called after that.
  82   virtual void Decode(const scoped_refptr<DecoderBuffer>& buffer,
  83                       const DecodeCB& decode_cb) = 0;
  84
  85   // Resets decoder state. All pending Decode() requests will be finished or
  86   // aborted before |closure| is called.
  87   // Note: No VideoDecoder calls should be made before |closure| is executed.
  88   virtual void Reset(const base::Closure& closure) = 0;
  89
  90   // Returns true if the decoder needs bitstream conversion before decoding.
  91   virtual bool NeedsBitstreamConversion() const;
  92
  93   // Returns true if the decoder currently has the ability to decode and return
  94   // a VideoFrame. Most implementations can allocate a new VideoFrame and hence
  95   // this will always return true. Override and return false for decoders that
  96   // use a fixed set of VideoFrames for decoding.
  97   virtual bool CanReadWithoutStalling() const;
  98
  99   // Returns maximum number of parallel decode requests.
 100   virtual int GetMaxDecodeRequests() const;
 101
 102  private:
 103   DISALLOW_COPY_AND_ASSIGN(VideoDecoder);
 104 };
 105
 106 }  // namespace media
 107
 108 #endif  // MEDIA_BASE_VIDEO_DECODER_H_