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/size.h"
15
16namespace media {
17
18class DecoderBuffer;
19class VideoDecoderConfig;
20class VideoFrame;
21
22class 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    kDecryptError  // Decrypting error happened.
32  };
33
34  // Callback for VideoDecoder to return a decoded frame whenever it becomes
35  // available. Only non-EOS frames should be returned via this callback.
36  typedef base::Callback<void(const scoped_refptr<VideoFrame>&)> OutputCB;
37
38  // Callback type for Decode(). Called after the decoder has completed decoding
39  // corresponding DecoderBuffer, indicating that it's ready to accept another
40  // buffer to decode.
41  typedef base::Callback<void(Status status)> DecodeCB;
42
43  VideoDecoder();
44
45  // Fires any pending callbacks, stops and destroys the decoder.
46  // Note: Since this is a destructor, |this| will be destroyed after this call.
47  // Make sure the callbacks fired from this call doesn't post any task that
48  // depends on |this|.
49  virtual ~VideoDecoder();
50
51  // Returns the name of the decoder for logging purpose.
52  virtual std::string GetDisplayName() const = 0;
53
54  // Initializes a VideoDecoder with the given |config|, executing the
55  // |status_cb| upon completion. |output_cb| is called for each output frame
56  // decoded by Decode().
57  //
58  // Note:
59  // 1) The VideoDecoder will be reinitialized if it was initialized before.
60  //    Upon reinitialization, all internal buffered frames will be dropped.
61  // 2) This method should not be called during pending decode or reset.
62  // 3) No VideoDecoder calls should be made before |status_cb| is executed.
63  virtual void Initialize(const VideoDecoderConfig& config,
64                          bool low_delay,
65                          const PipelineStatusCB& status_cb,
66                          const OutputCB& output_cb) = 0;
67
68  // Requests a |buffer| to be decoded. The status of the decoder and decoded
69  // frame are returned via the provided callback. Some decoders may allow
70  // decoding multiple buffers in parallel. Callers should call
71  // GetMaxDecodeRequests() to get number of buffers that may be decoded in
72  // parallel. Decoder must call |decode_cb| in the same order in which Decode()
73  // is called.
74  //
75  // Implementations guarantee that the callback will not be called from within
76  // this method and that |decode_cb| will not be blocked on the following
77  // Decode() calls (i.e. |decode_cb| will be called even if Decode() is never
78  // called again).
79  //
80  // After decoding is finished the decoder calls |output_cb| specified in
81  // Initialize() for each decoded frame. |output_cb| may be called before or
82  // after |decode_cb|.
83  //
84  // If |buffer| is an EOS buffer then the decoder must be flushed, i.e.
85  // |output_cb| must be called for each frame pending in the queue and
86  // |decode_cb| must be called after that. Callers will not call Decode()
87  // again until after the flush completes.
88  virtual void Decode(const scoped_refptr<DecoderBuffer>& buffer,
89                      const DecodeCB& decode_cb) = 0;
90
91  // Resets decoder state. All pending Decode() requests will be finished or
92  // aborted before |closure| is called.
93  // Note: No VideoDecoder calls should be made before |closure| is executed.
94  virtual void Reset(const base::Closure& closure) = 0;
95
96  // Returns true if the decoder needs bitstream conversion before decoding.
97  virtual bool NeedsBitstreamConversion() const;
98
99  // Returns true if the decoder currently has the ability to decode and return
100  // a VideoFrame. Most implementations can allocate a new VideoFrame and hence
101  // this will always return true. Override and return false for decoders that
102  // use a fixed set of VideoFrames for decoding.
103  virtual bool CanReadWithoutStalling() const;
104
105  // Returns maximum number of parallel decode requests.
106  virtual int GetMaxDecodeRequests() const;
107
108 private:
109  DISALLOW_COPY_AND_ASSIGN(VideoDecoder);
110};
111
112}  // namespace media
113
114#endif  // MEDIA_BASE_VIDEO_DECODER_H_
115