media/filters/ffmpeg_glue.h

   1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // FFmpegGlue is an adapter for FFmpeg's URLProtocol interface that allows us to
   6 // use a DataSource implementation with FFmpeg. For convenience we use FFmpeg's
   7 // av_open_input_file function, which analyzes the filename given to it and
   8 // automatically initializes the appropriate URLProtocol.
   9 //
  10 // Since the DataSource is already open by time we call av_open_input_file, we
  11 // need a way for av_open_input_file to find the correct DataSource instance.
  12 // The solution is to maintain a map of "filenames" to DataSource instances,
  13 // where filenames are actually just a unique identifier.  For simplicity,
  14 // FFmpegGlue is registered as an HTTP handler and generates filenames based on
  15 // the memory address of the DataSource, i.e., http://0xc0bf4870.  Since there
  16 // may be multiple FFmpegDemuxers active at one time, FFmpegGlue is a
  17 // thread-safe singleton.
  18 //
  19 // Usage: FFmpegDemuxer adds the DataSource to FFmpegGlue's map and is given a
  20 // filename to pass to av_open_input_file.  FFmpegDemuxer calls
  21 // av_open_input_file with the filename, which results in FFmpegGlue returning
  22 // the DataSource as a URLProtocol instance to FFmpeg.  Since FFmpegGlue is only
  23 // needed for opening files, when av_open_input_file returns FFmpegDemuxer
  24 // removes the DataSource from FFmpegGlue's map.
  25
  26 #ifndef MEDIA_FILTERS_FFMPEG_GLUE_H_
  27 #define MEDIA_FILTERS_FFMPEG_GLUE_H_
  28
  29 #include <map>
  30 #include <string>
  31
  32 #include "base/memory/singleton.h"
  33 #include "base/synchronization/lock.h"
  34 #include "media/base/media_export.h"
  35
  36 struct URLProtocol;
  37
  38 namespace media {
  39
  40 class MEDIA_EXPORT FFmpegURLProtocol {
  41  public:
  42   FFmpegURLProtocol() {}
  43
  44   virtual ~FFmpegURLProtocol() {}
  45
  46   // Read the given amount of bytes into data, returns the number of bytes read
  47   // if successful, kReadError otherwise.
  48   virtual size_t Read(size_t size, uint8* data) = 0;
  49
  50   // Returns true and the current file position for this file, false if the
  51   // file position could not be retrieved.
  52   virtual bool GetPosition(int64* position_out) = 0;
  53
  54   // Returns true if the file position could be set, false otherwise.
  55   virtual bool SetPosition(int64 position) = 0;
  56
  57   // Returns true and the file size, false if the file size could not be
  58   // retrieved.
  59   virtual bool GetSize(int64* size_out) = 0;
  60
  61   // Returns false if this protocol supports random seeking.
  62   virtual bool IsStreaming() = 0;
  63
  64  private:
  65   DISALLOW_COPY_AND_ASSIGN(FFmpegURLProtocol);
  66 };
  67
  68 class MEDIA_EXPORT FFmpegGlue {
  69  public:
  70   // Returns the singleton instance.
  71   static FFmpegGlue* GetInstance();
  72
  73   // Adds a FFmpegProtocol to the FFmpeg glue layer and returns a unique string
  74   // that can be passed to FFmpeg to identify the data source.
  75   std::string AddProtocol(FFmpegURLProtocol* protocol);
  76
  77   // Removes a FFmpegProtocol from the FFmpeg glue layer.  Using strings from
  78   // previously added FFmpegProtocols will no longer work.
  79   void RemoveProtocol(FFmpegURLProtocol* protocol);
  80
  81   // Assigns the FFmpegProtocol identified with by the given key to
  82   // |protocol|, or assigns NULL if no such FFmpegProtocol could be found.
  83   void GetProtocol(const std::string& key,
  84                    FFmpegURLProtocol** protocol);
  85
  86  private:
  87   // Only allow Singleton to create and delete FFmpegGlue.
  88   friend struct DefaultSingletonTraits<FFmpegGlue>;
  89   FFmpegGlue();
  90   virtual ~FFmpegGlue();
  91
  92   // Returns the unique key for this data source, which can be passed to
  93   // av_open_input_file as the filename.
  94   std::string GetProtocolKey(FFmpegURLProtocol* protocol);
  95
  96   // Mutual exclusion while adding/removing items from the map.
  97   base::Lock lock_;
  98
  99   // Map between keys and FFmpegProtocol references.
 100   typedef std::map<std::string, FFmpegURLProtocol*> ProtocolMap;
 101   ProtocolMap protocols_;
 102
 103   friend class FFmpegGlueTest;
 104   static URLProtocol* url_protocol();
 105
 106   DISALLOW_COPY_AND_ASSIGN(FFmpegGlue);
 107 };
 108
 109 }  // namespace media
 110
 111 #endif  // MEDIA_FILTERS_FFMPEG_GLUE_H_