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// Copyright (c) 2009 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.
// FFmpegGlue is an adapter for FFmpeg's URLProtocol interface that allows us to
// use a DataSource implementation with FFmpeg. For convenience we use FFmpeg's
// av_open_input_file function, which analyzes the filename given to it and
// automatically initializes the appropriate URLProtocol.
//
// Since the DataSource is already open by time we call av_open_input_file, we
// need a way for av_open_input_file to find the correct DataSource instance.
// The solution is to maintain a map of "filenames" to DataSource instances,
// where filenames are actually just a unique identifier. For simplicity,
// FFmpegGlue is registered as an HTTP handler and generates filenames based on
// the memory address of the DataSource, i.e., http://0xc0bf4870. Since there
// may be multiple FFmpegDemuxers active at one time, FFmpegGlue is a
// thread-safe singleton.
//
// Usage: FFmpegDemuxer adds the DataSource to FFmpegGlue's map and is given a
// filename to pass to av_open_input_file. FFmpegDemuxer calls
// av_open_input_file with the filename, which results in FFmpegGlue returning
// the DataSource as a URLProtocol instance to FFmpeg. Since FFmpegGlue is only
// needed for opening files, when av_open_input_file returns FFmpegDemuxer
// removes the DataSource from FFmpegGlue's map.
#ifndef MEDIA_FILTERS_FFMPEG_GLUE_H_
#define MEDIA_FILTERS_FFMPEG_GLUE_H_
#include <map>
#include <string>
#include "base/lock.h"
#include "base/singleton.h"
// FFmpeg forward declarations.
struct URLContext;
typedef int64 offset_t;
namespace media {
class DataSource;
class FFmpegGlue : public Singleton<FFmpegGlue> {
public:
// Adds a DataSource to the FFmpeg glue layer and returns a unique string that
// can be passed to FFmpeg to identify the data source.
std::string AddDataSource(DataSource* data_source);
// Removes a DataSource from the FFmpeg glue layer. Using strings from
// previously added DataSources will no longer work.
void RemoveDataSource(DataSource* data_source);
// Assigns the DataSource identified with by the given key to |data_source|,
// or assigns NULL if no such DataSource could be found.
void GetDataSource(const std::string& key,
scoped_refptr<DataSource>* data_source);
private:
// Only allow Singleton to create and delete FFmpegGlue.
friend struct DefaultSingletonTraits<FFmpegGlue>;
FFmpegGlue();
virtual ~FFmpegGlue();
// Returns the unique key for this data source, which can be passed to
// av_open_input_file as the filename.
std::string GetDataSourceKey(DataSource* data_source);
// Mutual exclusion while adding/removing items from the map.
Lock lock_;
// Map between keys and DataSource references.
typedef std::map< std::string, scoped_refptr<DataSource> > DataSourceMap;
DataSourceMap data_sources_;
DISALLOW_COPY_AND_ASSIGN(FFmpegGlue);
};
} // namespace media
#endif // MEDIA_FILTERS_FFMPEG_GLUE_H_
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