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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/callback.h"
#include "base/memory/ref_counted.h"
#include "media/base/pipeline_status.h"
#include "media/base/media_export.h"
#include "ui/gfx/size.h"
namespace media {
class Buffer;
class DemuxerStream;
class VideoFrame;
class MEDIA_EXPORT VideoDecoder
: public base::RefCountedThreadSafe<VideoDecoder> {
public:
// Status codes for read operations on VideoDecoder.
enum DecoderStatus {
kOk, // Everything went as planned.
kDecodeError, // Decoding error happened.
kDecryptError // Decrypting error happened.
};
// Initialize a VideoDecoder with the given DemuxerStream, executing the
// callback upon completion.
// statistics_cb is used to update global pipeline statistics.
virtual void Initialize(const scoped_refptr<DemuxerStream>& stream,
const PipelineStatusCB& status_cb,
const StatisticsCB& statistics_cb) = 0;
// Requests a frame to be decoded. The status of the decoder and decoded frame
// are returned via the provided callback. Only one read may be in flight at
// any given time.
//
// Implementations guarantee that the callback will not be called from within
// this method.
//
// If the returned status is not kOk, some error has occurred in the video
// decoder. In this case, the returned frame should always be NULL.
//
// Otherwise, the video decoder is in good shape. In this case, Non-NULL
// frames contain decoded video data or may indicate the end of the stream.
// NULL video frames indicate an aborted read. This can happen if the
// DemuxerStream gets flushed and doesn't have any more data to return.
typedef base::Callback<void(DecoderStatus, scoped_refptr<VideoFrame>)> ReadCB;
virtual void Read(const ReadCB& read_cb) = 0;
// Reset decoder state, fulfilling all pending ReadCB and dropping extra
// queued decoded data. After this call, the decoder is back to an initialized
// clean state.
virtual void Reset(const base::Closure& closure) = 0;
// Stop decoder and set it to an uninitialized state. Note that a VideoDecoder
// should/could not be re-initialized after it has been stopped.
virtual void Stop(const base::Closure& closure) = 0;
// Returns the natural width and height of decoded video in pixels.
//
// Clients should NOT rely on these values to remain constant. Instead, use
// the width/height from decoded video frames themselves.
//
// TODO(scherkus): why not rely on prerolling and decoding a single frame to
// get dimensions?
virtual const gfx::Size& natural_size() = 0;
// Returns true if the output format has an alpha channel. Most formats do not
// have alpha so the default is false. Override and return true for decoders
// that return formats with an alpha channel.
virtual bool HasAlpha() const;
// Prepare decoder for shutdown. This is a HACK needed because
// PipelineImpl::Stop() goes through a Pause/Flush/Stop dance to all its
// filters, waiting for each state transition to complete before starting the
// next, but WebMediaPlayerImpl::Destroy() holds the renderer loop hostage for
// the duration. Default implementation does nothing; derived decoders may
// override as needed. http://crbug.com/110228 tracks removing this.
virtual void PrepareForShutdownHack();
protected:
friend class base::RefCountedThreadSafe<VideoDecoder>;
virtual ~VideoDecoder();
VideoDecoder();
DISALLOW_COPY_AND_ASSIGN(VideoDecoder);
};
} // namespace media
#endif // MEDIA_BASE_VIDEO_DECODER_H_
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