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 <string>
   9
  10 #include "base/callback.h"
  11 #include "base/memory/ref_counted.h"
  12 #include "media/base/media_export.h"
  13 #include "media/base/pipeline_status.h"
  14 #include "ui/gfx/geometry/size.h"
  15
  16 namespace media {
  17
  18 class DecoderBuffer;
  19 class VideoDecoderConfig;
  20 class VideoFrame;
  21
  22 class MEDIA_EXPORT VideoDecoder {
  23  public:
  24   // Status codes for decode operations on VideoDecoder.
  25   // TODO(rileya): Now that both AudioDecoder and VideoDecoder Status enums
  26   // match, break them into a decoder_status.h.
  27   enum Status {
  28     kOk,          // Everything went as planned.
  29     kAborted,     // Decode was aborted as a result of Reset() being called.
  30     kDecodeError  // Decoding error happened.
  31   };
  32
  33   // Callback for VideoDecoder initialization.
  34   typedef base::Callback<void(bool success)> InitCB;
  35
  36   // Callback for VideoDecoder to return a decoded frame whenever it becomes
  37   // available. Only non-EOS frames should be returned via this callback.
  38   typedef base::Callback<void(const scoped_refptr<VideoFrame>&)> OutputCB;
  39
  40   // Callback type for Decode(). Called after the decoder has completed decoding
  41   // corresponding DecoderBuffer, indicating that it's ready to accept another
  42   // buffer to decode.
  43   typedef base::Callback<void(Status status)> DecodeCB;
  44
  45   VideoDecoder();
  46
  47   // Fires any pending callbacks, stops and destroys the decoder.
  48   // Note: Since this is a destructor, |this| will be destroyed after this call.
  49   // Make sure the callbacks fired from this call doesn't post any task that
  50   // depends on |this|.
  51   virtual ~VideoDecoder();
  52
  53   // Returns the name of the decoder for logging purpose.
  54   virtual std::string GetDisplayName() const = 0;
  55
  56   // Initializes a VideoDecoder with the given |config|, executing the
  57   // |init_cb| upon completion. |output_cb| is called for each output frame
  58   // decoded by Decode().
  59   //
  60   // If |low_delay| is true then the decoder is not allowed to queue frames,
  61   // except for out-of-order frames, i.e. if the next frame can be returned it
  62   // must be returned without waiting for Decode() to be called again.
  63   // Initialization should fail if |low_delay| is true and the decoder cannot
  64   // satisfy the requirements above.
  65   //
  66   // Note:
  67   // 1) The VideoDecoder will be reinitialized if it was initialized before.
  68   //    Upon reinitialization, all internal buffered frames will be dropped.
  69   // 2) This method should not be called during pending decode or reset.
  70   // 3) No VideoDecoder calls should be made before |init_cb| is executed.
  71   virtual void Initialize(const VideoDecoderConfig& config,
  72                           bool low_delay,
  73                           const InitCB& init_cb,
  74                           const OutputCB& output_cb) = 0;
  75
  76   // Requests a |buffer| to be decoded. The status of the decoder and decoded
  77   // frame are returned via the provided callback. Some decoders may allow
  78   // decoding multiple buffers in parallel. Callers should call
  79   // GetMaxDecodeRequests() to get number of buffers that may be decoded in
  80   // parallel. Decoder must call |decode_cb| in the same order in which Decode()
  81   // is called.
  82   //
  83   // Implementations guarantee that the callback will not be called from within
  84   // this method and that |decode_cb| will not be blocked on the following
  85   // Decode() calls (i.e. |decode_cb| will be called even if Decode() is never
  86   // called again).
  87   //
  88   // After decoding is finished the decoder calls |output_cb| specified in
  89   // Initialize() for each decoded frame. In general |output_cb| may be called
  90   // before or after |decode_cb|, but software decoders normally call
  91   // |output_cb| before calling |decode_cb|, i.e. while Decode() is pending.
  92   //
  93   // If |buffer| is an EOS buffer then the decoder must be flushed, i.e.
  94   // |output_cb| must be called for each frame pending in the queue and
  95   // |decode_cb| must be called after that. Callers will not call Decode()
  96   // again until after the flush completes.
  97   virtual void Decode(const scoped_refptr<DecoderBuffer>& buffer,
  98                       const DecodeCB& decode_cb) = 0;
  99
 100   // Resets decoder state. All pending Decode() requests will be finished or
 101   // aborted before |closure| is called.
 102   // Note: No VideoDecoder calls should be made before |closure| is executed.
 103   virtual void Reset(const base::Closure& closure) = 0;
 104
 105   // Returns true if the decoder needs bitstream conversion before decoding.
 106   virtual bool NeedsBitstreamConversion() const;
 107
 108   // Returns true if the decoder currently has the ability to decode and return
 109   // a VideoFrame. Most implementations can allocate a new VideoFrame and hence
 110   // this will always return true. Override and return false for decoders that
 111   // use a fixed set of VideoFrames for decoding.
 112   virtual bool CanReadWithoutStalling() const;
 113
 114   // Returns maximum number of parallel decode requests.
 115   virtual int GetMaxDecodeRequests() const;
 116
 117  private:
 118   DISALLOW_COPY_AND_ASSIGN(VideoDecoder);
 119 };
 120
 121 }  // namespace media
 122
 123 #endif  // MEDIA_BASE_VIDEO_DECODER_H_