在iOS上使用Ogg打包Speex

Question

我正在使用libogg和libogg,我已成功将这些库添加到我的iPhone xCode项目中并用Speex编码我的声音.问题是我无法弄清楚如何使用ogg包装这些音频数据包.有人知道这种包应该是什么样子,或者有我可以使用的参考代码.

我知道在Java中它很简单(你有专门的功能),但在iOS上却没有.请帮忙.

Answer 1

UPD 2013年9月10日:请参见演示项目,基本上采用PCM audiodata从波的容器中,Speex编解码器进行编码,并打包到一切OGG容器.也许以后我会为IOS上的所有speex例程创建一个完整的库/框架.

UPD 16.02.2015:演示项目在GitHub上重新发布.

我最近也在iOS上尝试过Speex,取得了不同程度的成功,但这是我发现的东西.基本上,如果你想将一些speex编码的语音打包成一个ogg文件,你需要遵循三个步骤(假设libogg和libspeex已经编译并添加到项目中).

1)使用Speex标题添加第一个ogg页面; libspeex为它提供了内置工具(下面的代码来自我的项目,不是最优的,只是为了举例):

// create speex header 
SpeexHeader spxHeader;
SpeexMode spxMode = speex_wb_mode;
int spxRate = 16000;
int spxNumberOfChannels = 1;
speex_init_header(&spxHeader, spxRate, spxNumberOfChannels, &spxMode);

// set audio and ogg packing parameters
spxHeader.vbr = 0;
spxHeader.bitrate = 16;
spxHeader.frame_size = 320;
spxHeader.frames_per_packet = 1;

// wrap speex header in ogg packet
int oggPacketSize;
_oggPacket.packet = (unsigned char *)speex_header_to_packet(&spxHeader, &oggPacketSize);
_oggPacket.bytes = oggPacketSize;
_oggPacket.b_o_s = 1;
_oggPacket.e_o_s = 0;
_oggPacket.granulepos = 0;
_oggPacket.packetno = 0;

// submit the packet to the ogg streaming layer
ogg_stream_packetin(&_oggStreamState, &_oggPacket);
free(_oggPacket.packet);

// form an ogg page
ogg_stream_flush(&_oggStreamState, &_oggPage);

// write the page to file
[_oggFile appendBytes:&_oggStreamState.header length:_oggStreamState.header_fill];
[_oggFile appendBytes:_oggStreamState.body_data length:_oggStreamState.body_fill];

2)使用Vorbis评论添加第二个ogg页面:

// form any comment you like (I use custom struct with all fields)
vorbisCommentStruct *vorbisComment = calloc(sizeof(vorbisCommentStruct), sizeof(char));
...

// wrap Vorbis comment in ogg packet
_oggPacket.packet = (unsigned char *)vorbisComment;
_oggPacket.bytes = vorbisCommentLength;
_oggPacket.b_o_s = 0;
_oggPacket.e_o_s = 0;
_oggPacket.granulepos = 0;
_oggPacket.packetno = _oggStreamState.packetno;

// the rest should be same as in previous step
...

3)以类似的方式添加带有speex编码音频的后续ogg页面.

首先要确定每个ogg页面上你想要拥有音频数据的帧数(0-255;我选择任意79个):

_framesPerOggPage = 79;

然后为每个帧:

// calculate current granule position of audio data within ogg file 
int curGranulePos = _spxSamplesPerFrame * _oggTotalFramesCount;

// wrap audio data in ogg packet
oggPacket.packet = (unsigned char *)spxFrame;
oggPacket.bytes = spxFrameLength;
oggPacket.granulepos = curGranulePos;
oggPacket.packetno = _oggStreamState.packetno;
oggPacket.b_o_s = 0;
oggPacket.e_o_s = 0;

// submit packets to streaming layer until their number reaches _framesPerOggPage
...

// if we've reached this limit, we're ready to create another ogg page

ogg_stream_flush(&_oggStreamState, &_oggPage);

[_oggFile appendBytes:&_oggStreamState.header length:_oggStreamState.header_fill];
[_oggFile appendBytes:_oggStreamState.body_data length:_oggStreamState.body_fill];

// finally, if this is the last frame, flush all remaining packets,
// which have been created but not packed into a page, to the last page 
// (don't forget to set oggPacket.e_o_s to 1 for this frame)

而已.希望它会有所帮助.欢迎任何更正或问题.