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     kNotEnoughData,  // Not enough data to produce a video frame.
  29     kDecodeError,  // Decoding error happened.
  30     kDecryptError  // Decrypting error happened.
  31   };
  32
  33   VideoDecoder();
  34   virtual ~VideoDecoder();
  35
  36   // Initializes a VideoDecoder with the given |config|, executing the
  37   // |status_cb| upon completion.
  38   //
  39   // Note:
  40   // 1) The VideoDecoder will be reinitialized if it was initialized before.
  41   //    Upon reinitialization, all internal buffered frames will be dropped.
  42   // 2) This method should not be called during pending decode, reset or stop.
  43   // 3) No VideoDecoder calls except for Stop() should be made before
  44   //    |status_cb| is executed.
  45   virtual void Initialize(const VideoDecoderConfig& config,
  46                           bool low_delay,
  47                           const PipelineStatusCB& status_cb) = 0;
  48
  49   // Requests a |buffer| to be decoded. The status of the decoder and decoded
  50   // frame are returned via the provided callback. Some decoders may allow
  51   // decoding multiple buffers in parallel. Callers should call
  52   // GetMaxDecodeRequests() to get number of buffers that may be decoded in
  53   // parallel. Decoder must call |decode_cb| in the same order in which Decode()
  54   // is called.
  55   //
  56   // Implementations guarantee that the callback will not be called from within
  57   // this method and that |decode_cb| will not be blocked on the following
  58   // Decode() calls (i.e. |decode_cb| will be called even Decode() is never
  59   // called again).
  60   //
  61   // If the returned status is kOk:
  62   // - Non-EOS (end of stream) frame contains decoded video data.
  63   // - EOS frame indicates the end of the stream.
  64   // Otherwise the returned frame must be NULL.
  65   typedef base::Callback<void(Status,
  66                               const scoped_refptr<VideoFrame>&)> DecodeCB;
  67   virtual void Decode(const scoped_refptr<DecoderBuffer>& buffer,
  68                       const DecodeCB& decode_cb) = 0;
  69
  70   // Some VideoDecoders may queue up multiple VideoFrames from a single
  71   // DecoderBuffer, if we have any such queued frames this will return the next
  72   // one. Otherwise we return a NULL VideoFrame.
  73   //
  74   // TODO(xhwang): Revisit this method.
  75   virtual scoped_refptr<VideoFrame> GetDecodeOutput();
  76
  77   // Resets decoder state, fulfilling all pending DecodeCB and dropping extra
  78   // queued decoded data. After this call, the decoder is back to an initialized
  79   // clean state.
  80   // Note: No VideoDecoder calls should be made before |closure| is executed.
  81   virtual void Reset(const base::Closure& closure) = 0;
  82
  83   // Stops decoder, fires any pending callbacks and sets the decoder to an
  84   // uninitialized state. A VideoDecoder cannot be re-initialized after it has
  85   // been stopped.
  86   // Note that if Initialize() is pending or has finished successfully, Stop()
  87   // must be called before destructing the decoder.
  88   virtual void Stop() = 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_