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- // 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<void(DecoderStatus)>;
- // 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<void(scoped_refptr<VideoFrame>)>;
- // 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<void(DecoderStatus)>;
- 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<DecoderBuffer> 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_
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