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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 <string>
#include "base/callback.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "media/base/media_export.h"
#include "media/base/pipeline_status.h"
#include "ui/gfx/geometry/size.h"
namespace media {
class CdmContext;
class DecoderBuffer;
class VideoDecoderConfig;
class VideoFrame;
class MEDIA_EXPORT VideoDecoder {
public:
// Status codes for decode operations on VideoDecoder.
// TODO(rileya): Now that both AudioDecoder and VideoDecoder Status enums
// match, break them into a decoder_status.h.
enum Status {
kOk, // Everything went as planned.
kAborted, // Decode was aborted as a result of Reset() being called.
kDecodeError // Decoding error happened.
};
// Callback for VideoDecoder initialization.
typedef base::Callback<void(bool success)> InitCB;
// Callback for VideoDecoder to return a decoded frame whenever it becomes
// available. Only non-EOS frames should be returned via this callback.
typedef base::Callback<void(const scoped_refptr<VideoFrame>&)> OutputCB;
// Callback type for Decode(). Called after the decoder has completed decoding
// corresponding DecoderBuffer, indicating that it's ready to accept another
// buffer to decode.
typedef base::Callback<void(Status status)> DecodeCB;
VideoDecoder();
// Fires any pending callbacks, stops and destroys the decoder.
// Note: Since this is a destructor, |this| will be destroyed after this call.
// Make sure the callbacks fired from this call doesn't post any task that
// depends on |this|.
virtual ~VideoDecoder();
// Returns the name of the decoder for logging purpose.
virtual std::string GetDisplayName() const = 0;
// 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.
//
// 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.
virtual void Initialize(const VideoDecoderConfig& config,
bool low_delay,
CdmContext* cdm_context,
const InitCB& init_cb,
const OutputCB& output_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. Decoder must call |decode_cb| in the same order in which Decode()
// is called.
//
// Implementations guarantee that the callback will not be called from within
// this method and that |decode_cb| will not be blocked on the following
// Decode() calls (i.e. |decode_cb| 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. In general |output_cb| may be called
// before or after |decode_cb|, but software decoders normally call
// |output_cb| before calling |decode_cb|, i.e. while Decode() is pending.
//
// 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(const scoped_refptr<DecoderBuffer>& buffer,
const 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(const base::Closure& 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;
private:
DISALLOW_COPY_AND_ASSIGN(VideoDecoder);
};
} // namespace media
#endif // MEDIA_BASE_VIDEO_DECODER_H_
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