// 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/memory/ref_counted.h" #include "media/base/decoder.h" #include "media/base/decoder_status.h" #include "media/base/media_export.h" #include "media/base/pipeline_status.h" #include "media/base/waiting.h" #include "ui/gfx/geometry/size.h" namespace media { class CdmContext; class DecoderBuffer; class VideoDecoderConfig; class VideoFrame; class MEDIA_EXPORT VideoDecoder : public Decoder { public: // Callback for Decoder initialization. using InitCB = base::OnceCallback; // Callback for VideoDecoder to return a decoded frame whenever it becomes // available. Only non-EOS frames should be returned via this callback. using OutputCB = base::RepeatingCallback)>; // Callback type for Decode(). Called after the decoder has completed decoding // corresponding DecoderBuffer, indicating that it's ready to accept another // buffer to decode. |kOk| implies success, |kAborted| implies that the // decode was aborted, which does not necessarily indicate an error. For // example, a Reset() can trigger this. Any other status code indicates that // the decoder encountered an error, and must be reset. using DecodeCB = base::OnceCallback; VideoDecoder(); VideoDecoder(const VideoDecoder&) = delete; VideoDecoder& operator=(const VideoDecoder&) = delete; ~VideoDecoder() override; // Initializes a VideoDecoder with the given |config|, executing the // |init_cb| upon completion. |output_cb| is called for each output frame // decoded by Decode(). // // If |low_delay| is true then the decoder is not allowed to queue frames, // except for out-of-order frames, i.e. if the next frame can be returned it // must be returned without waiting for Decode() to be called again. // Initialization should fail if |low_delay| is true and the decoder cannot // satisfy the requirements above. // // |cdm_context| can be used to handle encrypted buffers. May be null if the // stream is not encrypted. // // |waiting_cb| is called whenever the decoder is stalled waiting for // something, e.g. decryption key. May be called at any time after // Initialize(). // // 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 or reset. // 3) No VideoDecoder calls should be made before |init_cb| is executed. // 4) VideoDecoders should take care to run |output_cb| as soon as the frame // is ready (i.e. w/o thread trampolining) since it can strongly affect frame // delivery times with high-frame-rate material. See Decode() for additional // notes. // 5) |init_cb| may be called before this returns. virtual void Initialize(const VideoDecoderConfig& config, bool low_delay, CdmContext* cdm_context, InitCB init_cb, const OutputCB& output_cb, const WaitingCB& waiting_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. // // Implementations guarantee that the |decode_cb| will not be called from // within this method, and that it will be called even if 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|, including before Decode() returns. // // 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. Callers will not call Decode() // again until after the flush completes. virtual void Decode(scoped_refptr buffer, DecodeCB decode_cb) = 0; // Resets decoder state. All pending Decode() requests will be finished or // aborted before |closure| is called. // Note: No VideoDecoder calls should be made before |closure| is executed. virtual void Reset(base::OnceClosure closure) = 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; // If true, the VideoDecoder outputs frames that hold resources which must be // kept alive for as long as the decoder's client needs them. This is only // relevant for VideoDecoders owned directly by the MojoVideoDecoderService. virtual bool FramesHoldExternalResources() const; // Returns the recommended number of threads for software video decoding. If // the --video-threads command line option is specified and is valid, that // value is returned. Otherwise |desired_threads| is clamped to the number of // logical processors and then further clamped to // [|limits::kMinVideoDecodeThreads|, |limits::kMaxVideoDecodeThreads|]. static int GetRecommendedThreadCount(int desired_threads); // Returns the type of the decoder for statistics recording purposes. // For meta-decoders (those which wrap other decoders, ie, MojoVideoDecoder) // this should return the underlying type, if it is known, otherwise return // its own type. virtual VideoDecoderType GetDecoderType() const = 0; }; } // namespace media #endif // MEDIA_BASE_VIDEO_DECODER_H_