media/filters/ffmpeg_glue.h

   1 // Copyright (c) 2012 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 interface between FFmpeg and Chrome used to proxy FFmpeg's
   6 // read and seek requests to Chrome's internal data structures.  The glue works
   7 // through the AVIO interface provided by FFmpeg.
   8 //
   9 // AVIO works through a special AVIOContext created through avio_alloc_context()
  10 // which is attached to the AVFormatContext used for demuxing.  The AVIO context
  11 // is initialized with read and seek methods which FFmpeg calls when necessary.
  12 //
  13 // During OpenContext() FFmpegGlue will tell FFmpeg to use Chrome's AVIO context
  14 // by passing NULL in for the filename parameter to avformat_open_input().  All
  15 // FFmpeg operations using the configured AVFormatContext will then redirect
  16 // reads and seeks through the glue.
  17 //
  18 // The glue in turn processes those read and seek requests using the
  19 // FFmpegURLProtocol provided during construction.
  20 //
  21 // FFmpegGlue is also responsible for initializing FFmpeg, which is done once
  22 // per process.  Initialization includes: turning off log messages, registering
  23 // a lock manager, and finally registering all demuxers and codecs.
  24
  25 #ifndef MEDIA_FILTERS_FFMPEG_GLUE_H_
  26 #define MEDIA_FILTERS_FFMPEG_GLUE_H_
  27
  28 #include "base/basictypes.h"
  29 #include "base/memory/scoped_ptr.h"
  30 #include "media/base/media_export.h"
  31 #include "media/ffmpeg/ffmpeg_deleters.h"
  32
  33 struct AVFormatContext;
  34 struct AVIOContext;
  35
  36 namespace media {
  37
  38 class MEDIA_EXPORT FFmpegURLProtocol {
  39  public:
  40   // Read the given amount of bytes into data, returns the number of bytes read
  41   // if successful, kReadError otherwise.
  42   virtual int Read(int size, uint8* data) = 0;
  43
  44   // Returns true and the current file position for this file, false if the
  45   // file position could not be retrieved.
  46   virtual bool GetPosition(int64* position_out) = 0;
  47
  48   // Returns true if the file position could be set, false otherwise.
  49   virtual bool SetPosition(int64 position) = 0;
  50
  51   // Returns true and the file size, false if the file size could not be
  52   // retrieved.
  53   virtual bool GetSize(int64* size_out) = 0;
  54
  55   // Returns false if this protocol supports random seeking.
  56   virtual bool IsStreaming() = 0;
  57 };
  58
  59 class MEDIA_EXPORT FFmpegGlue {
  60  public:
  61   static void InitializeFFmpeg();
  62
  63   // See file documentation for usage.  |protocol| must outlive FFmpegGlue.
  64   explicit FFmpegGlue(FFmpegURLProtocol* protocol);
  65   ~FFmpegGlue();
  66
  67   // Opens an AVFormatContext specially prepared to process reads and seeks
  68   // through the FFmpegURLProtocol provided during construction.
  69   bool OpenContext();
  70   AVFormatContext* format_context() { return format_context_; }
  71
  72  private:
  73   bool open_called_;
  74   AVFormatContext* format_context_;
  75   scoped_ptr<AVIOContext, ScopedPtrAVFree> avio_context_;
  76
  77   DISALLOW_COPY_AND_ASSIGN(FFmpegGlue);
  78 };
  79
  80 }  // namespace media
  81
  82 #endif  // MEDIA_FILTERS_FFMPEG_GLUE_H_