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// Copyright (c) 2010 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_VIDEO_VIDEO_DECODE_CONTEXT_H_
#define MEDIA_VIDEO_VIDEO_DECODE_CONTEXT_H_
#include <vector>
#include "base/task.h"
#include "media/base/video_frame.h"
namespace media {
class VideoFrame;
// A VideoDecodeContext is used by VideoDecodeEngine to provide the following
// functions:
//
// 1. Provides access to hardware video decoding device.
// 2. Allocate VideoFrame objects that are used to carry the decoded video
// frames.
// 3. Upload a device specific buffer to some common VideoFrame storage types.
// In many cases a VideoDecodeEngine provides its own buffer, these buffer
// are usually device specific and a conversion step is needed. Instead of
// handling these many cases in the renderer a VideoDecodeContext is used
// to convert the device specific buffer to a common storage format, e.g.
// GL textures or system memory. This way we keep the device specific code
// in the VideoDecodeEngine and VideoDecodeContext pair.
class VideoDecodeContext {
public:
virtual ~VideoDecodeContext() {}
// Obtain a handle to the hardware video decoder device. The type of the
// handle is a contract between the implementation of VideoDecodeContext and
// VideoDecodeEngine.
//
// If a hardware device is not needed this method should return NULL.
virtual void* GetDevice() = 0;
// Allocate |n| video frames with dimension |width| and |height|. |task|
// is called when allocation has completed.
//
// |frames| is the output parameter for VideFrame(s) allocated.
virtual void AllocateVideoFrames(
int n, size_t width, size_t height, VideoFrame::Format format,
std::vector<scoped_refptr<VideoFrame> >* frames,
Task* task) = 0;
// Release all video frames allocated by the context. After making this call
// VideoDecodeEngine should not use the VideoFrame allocated because they
// could be destroyed.
virtual void ReleaseAllVideoFrames() = 0;
// Upload a device specific buffer to a video frame. The video frame was
// allocated via AllocateVideoFrames().
// This method is used if a VideoDecodeEngine cannot write directly to a
// VideoFrame, e.g. upload should be done on a different thread, the subsystem
// require some special treatment to generate a VideoFrame. The goal is to
// keep VideoDecodeEngine a reusable component and also adapt to different
// system by having a different VideoDecodeContext.
//
// |frame| is a VideoFrame allocated via AllocateVideoFrames().
//
// |buffer| is of type void*, it is of an internal type in VideoDecodeEngine
// that points to the buffer that contains the video frame.
// Implementor should know how to handle it.
//
// |task| is executed if the operation was completed successfully.
virtual void ConvertToVideoFrame(void* buffer,
scoped_refptr<VideoFrame> frame,
Task* task) = 0;
// Destroy this context asynchronously. When the operation is done |task|
// is called. It is safe to delete this object only after |task| is called.
//
// ReleaseVideoFrames() need to be called with all the video frames allocated
// before making this call.
virtual void Destroy(Task* task) = 0;
};
} // namespace media
#endif // MEDIA_VIDEO_VIDEO_DECODE_CONTEXT_H_
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