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
  32 struct AVFormatContext;
  33 struct AVIOContext;
  34
  35 namespace media {
  36
  37 class ScopedPtrAVFree;
  38
  39 class MEDIA_EXPORT FFmpegURLProtocol {
  40  public:
  41   // Read the given amount of bytes into data, returns the number of bytes read
  42   // if successful, kReadError otherwise.
  43   virtual int Read(int size, uint8* data) = 0;
  44
  45   // Returns true and the current file position for this file, false if the
  46   // file position could not be retrieved.
  47   virtual bool GetPosition(int64* position_out) = 0;
  48
  49   // Returns true if the file position could be set, false otherwise.
  50   virtual bool SetPosition(int64 position) = 0;
  51
  52   // Returns true and the file size, false if the file size could not be
  53   // retrieved.
  54   virtual bool GetSize(int64* size_out) = 0;
  55
  56   // Returns false if this protocol supports random seeking.
  57   virtual bool IsStreaming() = 0;
  58 };
  59
  60 class MEDIA_EXPORT FFmpegGlue {
  61  public:
  62   static void InitializeFFmpeg();
  63
  64   // See file documentation for usage.  |protocol| must outlive FFmpegGlue.
  65   explicit FFmpegGlue(FFmpegURLProtocol* protocol);
  66   ~FFmpegGlue();
  67
  68   // Opens an AVFormatContext specially prepared to process reads and seeks
  69   // through the FFmpegURLProtocol provided during construction.
  70   bool OpenContext();
  71   AVFormatContext* format_context() { return format_context_; }
  72
  73  private:
  74   bool open_called_;
  75   AVFormatContext* format_context_;
  76   scoped_ptr_malloc<AVIOContext, ScopedPtrAVFree> avio_context_;
  77
  78   DISALLOW_COPY_AND_ASSIGN(FFmpegGlue);
  79 };
  80
  81 }  // namespace media
  82
  83 #endif  // MEDIA_FILTERS_FFMPEG_GLUE_H_