【C】libFLAC的使用

0xAA55 · 发表于 2014-7-14 03:37:11

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1、什么是libFLAC？

libFLAC是用于操作FLAC文件的C开源工具。
libFLAC的官网：https://xiph.org/flac/

2、什么是FLAC？

FLAC是一种针对声音文件的无损压缩算法。压缩比略低于AAC，但是压缩和解压的速度很理想。使用FLAC压缩的无损音乐，体积将比没有经过压缩的无损音乐小很多（取决于音乐的平均音量。通常体积能减少到原文件的50%左右）。
相比较MP3有损压缩格式而言，FLAC能保留100%的音质。对于广大音乐爱好者而言，相对于MP3，FLAC是更好的选择。

libFLAC的源码请大家到libFLAC的官网下载。点此进入官方下载页面。
我这里有备用的下载地址。如果大家无法到官网下载libFLAC的源码，大家可以来我这里下载1.3.0版。强烈建议大家去官网下载最新版。

flac-1.3.0.tar.xz (1.03 MB, 下载次数: 29)

首先我们下载libFLAC的源码。然后用VS打开它的FLAC.sln这个文件。我用的是VS2012，因此出现了提示升级工程的对话框。我就将工程文件升级为VS2012的版本了。

看左边有很多工程。其中需要留意的是这几个工程：

C语言工程：
libFLAC_dynamic:编译它你能得到libFLAC.dll。这个DLL导出的函数可以帮你完成对FLAC文件的编码和解码的操作。
libFLAC_static:编译它，你能得到libFLAC.lib。当你既想操作FLAC文件，又不想让自己的程序依赖libFLAC.dll的时候，你可以使用它。
C++工程：
libFLAC++_dynamic:C++版的libFLAC.dll。功能和C语言版的一样，但是它是C++风格的，适合C++使用。
libFLAC++_static:C++版的libFLAC.lib。

这些是libFLAC的核心部分。当你展开它你会发现以下的文件：

这些文件是用NASM语法编写的汇编代码，用NASM编译，然后和C语言程序配合进行FLAC的编码和解码的。注意这是PC平台上的x86汇编。32位的。
我编译这个工程的时候NASM产生了“nasm.h:83: warning: COFF section names limited to 8 characters: truncating”这样的警告。意思是nasm.h第83行给段起名的时候超过了8个字符的长度，超出部分被截去。
这样的警告一般不会导致什么严重的错误，除非你为了编这个程序定义了各种奇怪的段，然后一不小心就冲突了。而这样的错误一般会被链接器发现，从而提示你进行修正。所以目前可以无视。

libFLAC的源码出现了NASM汇编代码，而且在很多地方出现了_asm内联汇编的语句，看似影响了移植性，其实这只是libFLAC用于优化代码运行效率的手段。
我们只需把C语言的预定义部分加上FLAC__NO_ASM，就能使其把原本用_asm内联汇编语句实现的部分用C代替了，从而保证了移植性。

本来libFLAC的源码里面附带的工程文件的配置是只有Win32平台编译的配置的。经过我的一系列处理（去掉NASM的部分使其不参与编译，然后通过调整预处理来使其不使用内联汇编）之后我编译出了64位的libFLAC.lib（静态链接库）。大家可以在这里下载。
x86:

libFLAC_static_1_3_0_x86.7z (176.17 KB, 下载次数: 12, 售价: 1 个宅币)
x64:

libFLAC_static_1_3_0_x64.7z (194.76 KB, 下载次数: 6, 售价: 2 个宅币)

要使用libFLAC进行C语言编程进行FLAC文件编码和解码，我们首先需要两样东西：编译时用到的头文件（.H）和链接时用到的库文件（.LIB，无论是动态DLL还是静态LIB）。
库文件请下载上面的。头文件，则在你刚下载的libFLAC的源码的include文件夹的FLAC文件夹内。
为了便于大家学习，我将头文件打包上传了。点此下载->

FLAC.7z (43.25 KB, 下载次数: 14)

头文件都是放在FLAC文件夹里面的。首先你把FLAC文件夹拷到你的工程文件夹。然后配置好你的工程，让它链接你的库文件。键人在此就不赘述了。

0x1：解码程序怎么写？

首先你需要包含一个头文件：#include"FLAC/stream_decoder.h"

FLAC的使用是围绕一个结构体进行的：FLAC__StreamDecoder *pDecoder;//FLAC解码器对象

FLAC是面向对象编程的思路。FLAC__StreamDecoder就是它所指的对象。首先我们需要调用FLAC__stream_decoder_new()来取得这个对象。

pDecoder=FLAC__stream_decoder_new();
if(!pDecoder)
{
fprintf(stderr,"初始化FLAC解码器失败！\n");
return;
}

取得的pDecoder就是我们所说的FLAC解码器对象了。切记在用完了pDecoder之后要记得把它删掉，否则就会占用内存。调用FLAC__stream_decoder_delete(pDecoder);就可以把它占用的部分删掉了。

然后就是它的初始化工作了。有以下几种初始化的函数可供选择：
FLAC__stream_decoder_init_stream:由用户自行将FLAC文件的内容输入，然后取得解码得到的波形数据。
FLAC__stream_decoder_init_ogg_stream:由用户自行将ogg FLAC文件的内容输入，然后取得解码得到的波形数据。
FLAC__stream_decoder_init_FILE:用户提供打开了FLAC文件的FILE*，然后FLAC解码器会自动从文件流读入数据，再解码。
FLAC__stream_decoder_init_ogg_FILE:用户提供打开了ogg FLAC文件的FILE*，然后FLAC解码器会自动从文件流读入数据，再解码。
FLAC__stream_decoder_init_file:用户只需提供FLAC文件的路径，FLAC解码器自动打开文件进行解码。
FLAC__stream_decoder_init_ogg_file:用户只需提供ogg FLAC文件的路径，FLAC解码器自动打开文件进行解码。
（PS.什么是ogg FLAC？）

这些函数都是以回调函数的方式运作的。用户只需提供回调函数，然后让它解码，最后等它调用你的回调函数就能取得解码的数据了。
我这里把这几个函数的原型贴出来。

/** Initialize the decoder instance to decode native FLAC streams.
*
* This flavor of initialization sets up the decoder to decode from a
* native FLAC stream. I/O is performed via callbacks to the client.
* For decoding from a plain file via filename or open FILE*,
* FLAC__stream_decoder_init_file() and FLAC__stream_decoder_init_FILE()
* provide a simpler interface.
*
* This function should be called after FLAC__stream_decoder_new() and
* FLAC__stream_decoder_set_*() but before any of the
* FLAC__stream_decoder_process_*() functions. Will set and return the
* decoder state, which will be FLAC__STREAM_DECODER_SEARCH_FOR_METADATA
* if initialization succeeded.
*
* \param decoder An uninitialized decoder instance.
* \param read_callback See FLAC__StreamDecoderReadCallback. This
* pointer must not be \c NULL.
* \param seek_callback See FLAC__StreamDecoderSeekCallback. This
* pointer may be \c NULL if seeking is not
* supported. If \a seek_callback is not \c NULL then a
* \a tell_callback, \a length_callback, and \a eof_callback must also be supplied.
* Alternatively, a dummy seek callback that just
* returns \c FLAC__STREAM_DECODER_SEEK_STATUS_UNSUPPORTED
* may also be supplied, all though this is slightly
* less efficient for the decoder.
* \param tell_callback See FLAC__StreamDecoderTellCallback. This
* pointer may be \c NULL if not supported by the client. If
* \a seek_callback is not \c NULL then a
* \a tell_callback must also be supplied.
* Alternatively, a dummy tell callback that just
* returns \c FLAC__STREAM_DECODER_TELL_STATUS_UNSUPPORTED
* may also be supplied, all though this is slightly
* less efficient for the decoder.
* \param length_callback See FLAC__StreamDecoderLengthCallback. This
* pointer may be \c NULL if not supported by the client. If
* \a seek_callback is not \c NULL then a
* \a length_callback must also be supplied.
* Alternatively, a dummy length callback that just
* returns \c FLAC__STREAM_DECODER_LENGTH_STATUS_UNSUPPORTED
* may also be supplied, all though this is slightly
* less efficient for the decoder.
* \param eof_callback See FLAC__StreamDecoderEofCallback. This
* pointer may be \c NULL if not supported by the client. If
* \a seek_callback is not \c NULL then a
* \a eof_callback must also be supplied.
* Alternatively, a dummy length callback that just
* returns \c false
* may also be supplied, all though this is slightly
* less efficient for the decoder.
* \param write_callback See FLAC__StreamDecoderWriteCallback. This
* pointer must not be \c NULL.
* \param metadata_callback See FLAC__StreamDecoderMetadataCallback. This
* pointer may be \c NULL if the callback is not
* desired.
* \param error_callback See FLAC__StreamDecoderErrorCallback. This
* pointer must not be \c NULL.
* \param client_data This value will be supplied to callbacks in their
* \a client_data argument.
* \assert
* \code decoder != NULL \endcode
* \retval FLAC__StreamDecoderInitStatus
* \c FLAC__STREAM_DECODER_INIT_STATUS_OK if initialization was successful;
* see FLAC__StreamDecoderInitStatus for the meanings of other return values.
*/
FLAC_API FLAC__StreamDecoderInitStatus FLAC__stream_decoder_init_stream(
FLAC__StreamDecoder *decoder,
FLAC__StreamDecoderReadCallback read_callback,
FLAC__StreamDecoderSeekCallback seek_callback,
FLAC__StreamDecoderTellCallback tell_callback,
FLAC__StreamDecoderLengthCallback length_callback,
FLAC__StreamDecoderEofCallback eof_callback,
FLAC__StreamDecoderWriteCallback write_callback,
FLAC__StreamDecoderMetadataCallback metadata_callback,
FLAC__StreamDecoderErrorCallback error_callback,
void *client_data
);
/** Initialize the decoder instance to decode Ogg FLAC streams.
*
* This flavor of initialization sets up the decoder to decode from a
* FLAC stream in an Ogg container. I/O is performed via callbacks to the
* client. For decoding from a plain file via filename or open FILE*,
* FLAC__stream_decoder_init_ogg_file() and FLAC__stream_decoder_init_ogg_FILE()
* provide a simpler interface.
*
* This function should be called after FLAC__stream_decoder_new() and
* FLAC__stream_decoder_set_*() but before any of the
* FLAC__stream_decoder_process_*() functions. Will set and return the
* decoder state, which will be FLAC__STREAM_DECODER_SEARCH_FOR_METADATA
* if initialization succeeded.
*
* \note Support for Ogg FLAC in the library is optional. If this
* library has been built without support for Ogg FLAC, this function
* will return \c FLAC__STREAM_DECODER_INIT_STATUS_UNSUPPORTED_CONTAINER.
*
* \param decoder An uninitialized decoder instance.
* \param read_callback See FLAC__StreamDecoderReadCallback. This
* pointer must not be \c NULL.
* \param seek_callback See FLAC__StreamDecoderSeekCallback. This
* pointer may be \c NULL if seeking is not
* supported. If \a seek_callback is not \c NULL then a
* \a tell_callback, \a length_callback, and \a eof_callback must also be supplied.
* Alternatively, a dummy seek callback that just
* returns \c FLAC__STREAM_DECODER_SEEK_STATUS_UNSUPPORTED
* may also be supplied, all though this is slightly
* less efficient for the decoder.
* \param tell_callback See FLAC__StreamDecoderTellCallback. This
* pointer may be \c NULL if not supported by the client. If
* \a seek_callback is not \c NULL then a
* \a tell_callback must also be supplied.
* Alternatively, a dummy tell callback that just
* returns \c FLAC__STREAM_DECODER_TELL_STATUS_UNSUPPORTED
* may also be supplied, all though this is slightly
* less efficient for the decoder.
* \param length_callback See FLAC__StreamDecoderLengthCallback. This
* pointer may be \c NULL if not supported by the client. If
* \a seek_callback is not \c NULL then a
* \a length_callback must also be supplied.
* Alternatively, a dummy length callback that just
* returns \c FLAC__STREAM_DECODER_LENGTH_STATUS_UNSUPPORTED
* may also be supplied, all though this is slightly
* less efficient for the decoder.
* \param eof_callback See FLAC__StreamDecoderEofCallback. This
* pointer may be \c NULL if not supported by the client. If
* \a seek_callback is not \c NULL then a
* \a eof_callback must also be supplied.
* Alternatively, a dummy length callback that just
* returns \c false
* may also be supplied, all though this is slightly
* less efficient for the decoder.
* \param write_callback See FLAC__StreamDecoderWriteCallback. This
* pointer must not be \c NULL.
* \param metadata_callback See FLAC__StreamDecoderMetadataCallback. This
* pointer may be \c NULL if the callback is not
* desired.
* \param error_callback See FLAC__StreamDecoderErrorCallback. This
* pointer must not be \c NULL.
* \param client_data This value will be supplied to callbacks in their
* \a client_data argument.
* \assert
* \code decoder != NULL \endcode
* \retval FLAC__StreamDecoderInitStatus
* \c FLAC__STREAM_DECODER_INIT_STATUS_OK if initialization was successful;
* see FLAC__StreamDecoderInitStatus for the meanings of other return values.
*/
FLAC_API FLAC__StreamDecoderInitStatus FLAC__stream_decoder_init_ogg_stream(
FLAC__StreamDecoder *decoder,
FLAC__StreamDecoderReadCallback read_callback,
FLAC__StreamDecoderSeekCallback seek_callback,
FLAC__StreamDecoderTellCallback tell_callback,
FLAC__StreamDecoderLengthCallback length_callback,
FLAC__StreamDecoderEofCallback eof_callback,
FLAC__StreamDecoderWriteCallback write_callback,
FLAC__StreamDecoderMetadataCallback metadata_callback,
FLAC__StreamDecoderErrorCallback error_callback,
void *client_data
);
/** Initialize the decoder instance to decode native FLAC files.
*
* This flavor of initialization sets up the decoder to decode from a
* plain native FLAC file. For non-stdio streams, you must use
* FLAC__stream_decoder_init_stream() and provide callbacks for the I/O.
*
* This function should be called after FLAC__stream_decoder_new() and
* FLAC__stream_decoder_set_*() but before any of the
* FLAC__stream_decoder_process_*() functions. Will set and return the
* decoder state, which will be FLAC__STREAM_DECODER_SEARCH_FOR_METADATA
* if initialization succeeded.
*
* \param decoder An uninitialized decoder instance.
* \param file An open FLAC file. The file should have been
* opened with mode \c "rb" and rewound. The file
* becomes owned by the decoder and should not be
* manipulated by the client while decoding.
* Unless \a file is \c stdin, it will be closed
* when FLAC__stream_decoder_finish() is called.
* Note however that seeking will not work when
* decoding from \c stdout since it is not seekable.
* \param write_callback See FLAC__StreamDecoderWriteCallback. This
* pointer must not be \c NULL.
* \param metadata_callback See FLAC__StreamDecoderMetadataCallback. This
* pointer may be \c NULL if the callback is not
* desired.
* \param error_callback See FLAC__StreamDecoderErrorCallback. This
* pointer must not be \c NULL.
* \param client_data This value will be supplied to callbacks in their
* \a client_data argument.
* \assert
* \code decoder != NULL \endcode
* \code file != NULL \endcode
* \retval FLAC__StreamDecoderInitStatus
* \c FLAC__STREAM_DECODER_INIT_STATUS_OK if initialization was successful;
* see FLAC__StreamDecoderInitStatus for the meanings of other return values.
*/
FLAC_API FLAC__StreamDecoderInitStatus FLAC__stream_decoder_init_FILE(
FLAC__StreamDecoder *decoder,
FILE *file,
FLAC__StreamDecoderWriteCallback write_callback,
FLAC__StreamDecoderMetadataCallback metadata_callback,
FLAC__StreamDecoderErrorCallback error_callback,
void *client_data
);
/** Initialize the decoder instance to decode Ogg FLAC files.
*
* This flavor of initialization sets up the decoder to decode from a
* plain Ogg FLAC file. For non-stdio streams, you must use
* FLAC__stream_decoder_init_ogg_stream() and provide callbacks for the I/O.
*
* This function should be called after FLAC__stream_decoder_new() and
* FLAC__stream_decoder_set_*() but before any of the
* FLAC__stream_decoder_process_*() functions. Will set and return the
* decoder state, which will be FLAC__STREAM_DECODER_SEARCH_FOR_METADATA
* if initialization succeeded.
*
* \note Support for Ogg FLAC in the library is optional. If this
* library has been built without support for Ogg FLAC, this function
* will return \c FLAC__STREAM_DECODER_INIT_STATUS_UNSUPPORTED_CONTAINER.
*
* \param decoder An uninitialized decoder instance.
* \param file An open FLAC file. The file should have been
* opened with mode \c "rb" and rewound. The file
* becomes owned by the decoder and should not be
* manipulated by the client while decoding.
* Unless \a file is \c stdin, it will be closed
* when FLAC__stream_decoder_finish() is called.
* Note however that seeking will not work when
* decoding from \c stdout since it is not seekable.
* \param write_callback See FLAC__StreamDecoderWriteCallback. This
* pointer must not be \c NULL.
* \param metadata_callback See FLAC__StreamDecoderMetadataCallback. This
* pointer may be \c NULL if the callback is not
* desired.
* \param error_callback See FLAC__StreamDecoderErrorCallback. This
* pointer must not be \c NULL.
* \param client_data This value will be supplied to callbacks in their
* \a client_data argument.
* \assert
* \code decoder != NULL \endcode
* \code file != NULL \endcode
* \retval FLAC__StreamDecoderInitStatus
* \c FLAC__STREAM_DECODER_INIT_STATUS_OK if initialization was successful;
* see FLAC__StreamDecoderInitStatus for the meanings of other return values.
*/
FLAC_API FLAC__StreamDecoderInitStatus FLAC__stream_decoder_init_ogg_FILE(
FLAC__StreamDecoder *decoder,
FILE *file,
FLAC__StreamDecoderWriteCallback write_callback,
FLAC__StreamDecoderMetadataCallback metadata_callback,
FLAC__StreamDecoderErrorCallback error_callback,
void *client_data
);
/** Initialize the decoder instance to decode native FLAC files.
*
* This flavor of initialization sets up the decoder to decode from a plain
* native FLAC file. If POSIX fopen() semantics are not sufficient, (for
* example, with Unicode filenames on Windows), you must use
* FLAC__stream_decoder_init_FILE(), or FLAC__stream_decoder_init_stream()
* and provide callbacks for the I/O.
*
* This function should be called after FLAC__stream_decoder_new() and
* FLAC__stream_decoder_set_*() but before any of the
* FLAC__stream_decoder_process_*() functions. Will set and return the
* decoder state, which will be FLAC__STREAM_DECODER_SEARCH_FOR_METADATA
* if initialization succeeded.
*
* \param decoder An uninitialized decoder instance.
* \param filename The name of the file to decode from. The file will
* be opened with fopen(). Use \c NULL to decode from
* \c stdin. Note that \c stdin is not seekable.
* \param write_callback See FLAC__StreamDecoderWriteCallback. This
* pointer must not be \c NULL.
* \param metadata_callback See FLAC__StreamDecoderMetadataCallback. This
* pointer may be \c NULL if the callback is not
* desired.
* \param error_callback See FLAC__StreamDecoderErrorCallback. This
* pointer must not be \c NULL.
* \param client_data This value will be supplied to callbacks in their
* \a client_data argument.
* \assert
* \code decoder != NULL \endcode
* \retval FLAC__StreamDecoderInitStatus
* \c FLAC__STREAM_DECODER_INIT_STATUS_OK if initialization was successful;
* see FLAC__StreamDecoderInitStatus for the meanings of other return values.
*/
FLAC_API FLAC__StreamDecoderInitStatus FLAC__stream_decoder_init_file(
FLAC__StreamDecoder *decoder,
const char *filename,
FLAC__StreamDecoderWriteCallback write_callback,
FLAC__StreamDecoderMetadataCallback metadata_callback,
FLAC__StreamDecoderErrorCallback error_callback,
void *client_data
);
/** Initialize the decoder instance to decode Ogg FLAC files.
*
* This flavor of initialization sets up the decoder to decode from a plain
* Ogg FLAC file. If POSIX fopen() semantics are not sufficient, (for
* example, with Unicode filenames on Windows), you must use
* FLAC__stream_decoder_init_ogg_FILE(), or FLAC__stream_decoder_init_ogg_stream()
* and provide callbacks for the I/O.
*
* This function should be called after FLAC__stream_decoder_new() and
* FLAC__stream_decoder_set_*() but before any of the
* FLAC__stream_decoder_process_*() functions. Will set and return the
* decoder state, which will be FLAC__STREAM_DECODER_SEARCH_FOR_METADATA
* if initialization succeeded.
*
* \note Support for Ogg FLAC in the library is optional. If this
* library has been built without support for Ogg FLAC, this function
* will return \c FLAC__STREAM_DECODER_INIT_STATUS_UNSUPPORTED_CONTAINER.
*
* \param decoder An uninitialized decoder instance.
* \param filename The name of the file to decode from. The file will
* be opened with fopen(). Use \c NULL to decode from
* \c stdin. Note that \c stdin is not seekable.
* \param write_callback See FLAC__StreamDecoderWriteCallback. This
* pointer must not be \c NULL.
* \param metadata_callback See FLAC__StreamDecoderMetadataCallback. This
* pointer may be \c NULL if the callback is not
* desired.
* \param error_callback See FLAC__StreamDecoderErrorCallback. This
* pointer must not be \c NULL.
* \param client_data This value will be supplied to callbacks in their
* \a client_data argument.
* \assert
* \code decoder != NULL \endcode
* \retval FLAC__StreamDecoderInitStatus
* \c FLAC__STREAM_DECODER_INIT_STATUS_OK if initialization was successful;
* see FLAC__StreamDecoderInitStatus for the meanings of other return values.
*/
FLAC_API FLAC__StreamDecoderInitStatus FLAC__stream_decoder_init_ogg_file(
FLAC__StreamDecoder *decoder,
const char *filename,
FLAC__StreamDecoderWriteCallback write_callback,
FLAC__StreamDecoderMetadataCallback metadata_callback,
FLAC__StreamDecoderErrorCallback error_callback,
void *client_data
);

复制代码

大家可以通过看注释来了解它们的使用方式。

刚才只是初始化的设定而已。设置好初始化的操作以后，你要做的就是让libFLAC帮你解码。
有以下几种方式可以启动它的解码过程：
FLAC__stream_decoder_process_single:解码一个块，得到一个块的数据。
FLAC__stream_decoder_process_until_end_of_metadata:一直解码，直到元数据（metadata）的结尾。
FLAC__stream_decoder_process_until_end_of_stream:一直解码，直到流的结尾（整个文件解码完）
当你调用上面三个函数中的一个的时候，libFLAC就会开始帮你解码，调用你提供的回调函数，把解码得到的数据提供给你。

其中可以用于辅助解码的函数如下：
FLAC__stream_decoder_skip_single_frame:跳过一个块。
FLAC__stream_decoder_seek_absolute:定位到某一个样本处。

详细的来自头文件的信息：

/** Decode one metadata block or audio frame.
* This version instructs the decoder to decode a either a single metadata
* block or a single frame and stop, unless the callbacks return a fatal
* error or the read callback returns
* \c FLAC__STREAM_DECODER_READ_STATUS_END_OF_STREAM.
*
* As the decoder needs more input it will call the read callback.
* Depending on what was decoded, the metadata or write callback will be
* called with the decoded metadata block or audio frame.
*
* Unless there is a fatal read error or end of stream, this function
* will return once one whole frame is decoded. In other words, if the
* stream is not synchronized or points to a corrupt frame header, the
* decoder will continue to try and resync until it gets to a valid
* frame, then decode one frame, then return. If the decoder points to
* a frame whose frame CRC in the frame footer does not match the
* computed frame CRC, this function will issue a
* FLAC__STREAM_DECODER_ERROR_STATUS_FRAME_CRC_MISMATCH error to the
* error callback, and return, having decoded one complete, although
* corrupt, frame. (Such corrupted frames are sent as silence of the
* correct length to the write callback.)
*
* \param decoder An initialized decoder instance.
* \assert
* \code decoder != NULL \endcode
* \retval FLAC__bool
* \c false if any fatal read, write, or memory allocation error
* occurred (meaning decoding must stop), else \c true; for more
* information about the decoder, check the decoder state with
* FLAC__stream_decoder_get_state().
*/
FLAC_API FLAC__bool FLAC__stream_decoder_process_single(FLAC__StreamDecoder *decoder);
/** Decode until the end of the metadata.
* This version instructs the decoder to decode from the current position
* and continue until all the metadata has been read, or until the
* callbacks return a fatal error or the read callback returns
* \c FLAC__STREAM_DECODER_READ_STATUS_END_OF_STREAM.
*
* As the decoder needs more input it will call the read callback.
* As each metadata block is decoded, the metadata callback will be called
* with the decoded metadata.
*
* \param decoder An initialized decoder instance.
* \assert
* \code decoder != NULL \endcode
* \retval FLAC__bool
* \c false if any fatal read, write, or memory allocation error
* occurred (meaning decoding must stop), else \c true; for more
* information about the decoder, check the decoder state with
* FLAC__stream_decoder_get_state().
*/
FLAC_API FLAC__bool FLAC__stream_decoder_process_until_end_of_metadata(FLAC__StreamDecoder *decoder);
/** Decode until the end of the stream.
* This version instructs the decoder to decode from the current position
* and continue until the end of stream (the read callback returns
* \c FLAC__STREAM_DECODER_READ_STATUS_END_OF_STREAM), or until the
* callbacks return a fatal error.
*
* As the decoder needs more input it will call the read callback.
* As each metadata block and frame is decoded, the metadata or write
* callback will be called with the decoded metadata or frame.
*
* \param decoder An initialized decoder instance.
* \assert
* \code decoder != NULL \endcode
* \retval FLAC__bool
* \c false if any fatal read, write, or memory allocation error
* occurred (meaning decoding must stop), else \c true; for more
* information about the decoder, check the decoder state with
* FLAC__stream_decoder_get_state().
*/
FLAC_API FLAC__bool FLAC__stream_decoder_process_until_end_of_stream(FLAC__StreamDecoder *decoder);
/** Skip one audio frame.
* This version instructs the decoder to 'skip' a single frame and stop,
* unless the callbacks return a fatal error or the read callback returns
* \c FLAC__STREAM_DECODER_READ_STATUS_END_OF_STREAM.
*
* The decoding flow is the same as what occurs when
* FLAC__stream_decoder_process_single() is called to process an audio
* frame, except that this function does not decode the parsed data into
* PCM or call the write callback. The integrity of the frame is still
* checked the same way as in the other process functions.
*
* This function will return once one whole frame is skipped, in the
* same way that FLAC__stream_decoder_process_single() will return once
* one whole frame is decoded.
*
* This function can be used in more quickly determining FLAC frame
* boundaries when decoding of the actual data is not needed, for
* example when an application is separating a FLAC stream into frames
* for editing or storing in a container. To do this, the application
* can use FLAC__stream_decoder_skip_single_frame() to quickly advance
* to the next frame, then use
* FLAC__stream_decoder_get_decode_position() to find the new frame
* boundary.
*
* This function should only be called when the stream has advanced
* past all the metadata, otherwise it will return \c false.
*
* \param decoder An initialized decoder instance not in a metadata
* state.
* \assert
* \code decoder != NULL \endcode
* \retval FLAC__bool
* \c false if any fatal read, write, or memory allocation error
* occurred (meaning decoding must stop), or if the decoder
* is in the FLAC__STREAM_DECODER_SEARCH_FOR_METADATA or
* FLAC__STREAM_DECODER_READ_METADATA state, else \c true; for more
* information about the decoder, check the decoder state with
* FLAC__stream_decoder_get_state().
*/
FLAC_API FLAC__bool FLAC__stream_decoder_skip_single_frame(FLAC__StreamDecoder *decoder);
/** Flush the input and seek to an absolute sample.
* Decoding will resume at the given sample. Note that because of
* this, the next write callback may contain a partial block. The
* client must support seeking the input or this function will fail
* and return \c false. Furthermore, if the decoder state is
* \c FLAC__STREAM_DECODER_SEEK_ERROR, then the decoder must be flushed
* with FLAC__stream_decoder_flush() or reset with
* FLAC__stream_decoder_reset() before decoding can continue.
*
* \param decoder A decoder instance.
* \param sample The target sample number to seek to.
* \assert
* \code decoder != NULL \endcode
* \retval FLAC__bool
* \c true if successful, else \c false.
*/
FLAC_API FLAC__bool FLAC__stream_decoder_seek_absolute(FLAC__StreamDecoder *decoder, FLAC__uint64 sample);

复制代码

回调函数的原型详见libFLAC的头文件。里面有非常详细的介绍。你只需在VS里把光标放到这些函数类型上然后按下F12就能看到所有的信息。
不过为了便于理解，我把这些回调函数的原型也复制了过来。这样大家就不用亲自去按F12看信息了。直接看我的帖子就行。

/** Signature for the read callback.
*
* A function pointer matching this signature must be passed to
* FLAC__stream_decoder_init*_stream(). The supplied function will be
* called when the decoder needs more input data. The address of the
* buffer to be filled is supplied, along with the number of bytes the
* buffer can hold. The callback may choose to supply less data and
* modify the byte count but must be careful not to overflow the buffer.
* The callback then returns a status code chosen from
* FLAC__StreamDecoderReadStatus.
*
* Here is an example of a read callback for stdio streams:
* \code
* FLAC__StreamDecoderReadStatus read_cb(const FLAC__StreamDecoder *decoder, FLAC__byte buffer[], size_t *bytes, void *client_data)
* {
* FILE *file = ((MyClientData*)client_data)->file;
* if(*bytes > 0) {
* *bytes = fread(buffer, sizeof(FLAC__byte), *bytes, file);
* if(ferror(file))
* return FLAC__STREAM_DECODER_READ_STATUS_ABORT;
* else if(*bytes == 0)
* return FLAC__STREAM_DECODER_READ_STATUS_END_OF_STREAM;
* else
* return FLAC__STREAM_DECODER_READ_STATUS_CONTINUE;
* }
* else
* return FLAC__STREAM_DECODER_READ_STATUS_ABORT;
* }
* \endcode
*
* \note In general, FLAC__StreamDecoder functions which change the
* state should not be called on the \a decoder while in the callback.
*
* \param decoder The decoder instance calling the callback.
* \param buffer A pointer to a location for the callee to store
* data to be decoded.
* \param bytes A pointer to the size of the buffer. On entry
* to the callback, it contains the maximum number
* of bytes that may be stored in \a buffer. The
* callee must set it to the actual number of bytes
* stored (0 in case of error or end-of-stream) before
* returning.
* \param client_data The callee's client data set through
* FLAC__stream_decoder_init_*().
* \retval FLAC__StreamDecoderReadStatus
* The callee's return status. Note that the callback should return
* \c FLAC__STREAM_DECODER_READ_STATUS_END_OF_STREAM if and only if
* zero bytes were read and there is no more data to be read.
*/
typedef FLAC__StreamDecoderReadStatus (*FLAC__StreamDecoderReadCallback)(const FLAC__StreamDecoder *decoder, FLAC__byte buffer[], size_t *bytes, void *client_data);
/** Signature for the seek callback.
*
* A function pointer matching this signature may be passed to
* FLAC__stream_decoder_init*_stream(). The supplied function will be
* called when the decoder needs to seek the input stream. The decoder
* will pass the absolute byte offset to seek to, 0 meaning the
* beginning of the stream.
*
* Here is an example of a seek callback for stdio streams:
* \code
* FLAC__StreamDecoderSeekStatus seek_cb(const FLAC__StreamDecoder *decoder, FLAC__uint64 absolute_byte_offset, void *client_data)
* {
* FILE *file = ((MyClientData*)client_data)->file;
* if(file == stdin)
* return FLAC__STREAM_DECODER_SEEK_STATUS_UNSUPPORTED;
* else if(fseeko(file, (off_t)absolute_byte_offset, SEEK_SET) < 0)
* return FLAC__STREAM_DECODER_SEEK_STATUS_ERROR;
* else
* return FLAC__STREAM_DECODER_SEEK_STATUS_OK;
* }
* \endcode
*
* \note In general, FLAC__StreamDecoder functions which change the
* state should not be called on the \a decoder while in the callback.
*
* \param decoder The decoder instance calling the callback.
* \param absolute_byte_offset The offset from the beginning of the stream
* to seek to.
* \param client_data The callee's client data set through
* FLAC__stream_decoder_init_*().
* \retval FLAC__StreamDecoderSeekStatus
* The callee's return status.
*/
typedef FLAC__StreamDecoderSeekStatus (*FLAC__StreamDecoderSeekCallback)(const FLAC__StreamDecoder *decoder, FLAC__uint64 absolute_byte_offset, void *client_data);
/** Signature for the tell callback.
*
* A function pointer matching this signature may be passed to
* FLAC__stream_decoder_init*_stream(). The supplied function will be
* called when the decoder wants to know the current position of the
* stream. The callback should return the byte offset from the
* beginning of the stream.
*
* Here is an example of a tell callback for stdio streams:
* \code
* FLAC__StreamDecoderTellStatus tell_cb(const FLAC__StreamDecoder *decoder, FLAC__uint64 *absolute_byte_offset, void *client_data)
* {
* FILE *file = ((MyClientData*)client_data)->file;
* off_t pos;
* if(file == stdin)
* return FLAC__STREAM_DECODER_TELL_STATUS_UNSUPPORTED;
* else if((pos = ftello(file)) < 0)
* return FLAC__STREAM_DECODER_TELL_STATUS_ERROR;
* else {
* *absolute_byte_offset = (FLAC__uint64)pos;
* return FLAC__STREAM_DECODER_TELL_STATUS_OK;
* }
* }
* \endcode
*
* \note In general, FLAC__StreamDecoder functions which change the
* state should not be called on the \a decoder while in the callback.
*
* \param decoder The decoder instance calling the callback.
* \param absolute_byte_offset A pointer to storage for the current offset
* from the beginning of the stream.
* \param client_data The callee's client data set through
* FLAC__stream_decoder_init_*().
* \retval FLAC__StreamDecoderTellStatus
* The callee's return status.
*/
typedef FLAC__StreamDecoderTellStatus (*FLAC__StreamDecoderTellCallback)(const FLAC__StreamDecoder *decoder, FLAC__uint64 *absolute_byte_offset, void *client_data);
/** Signature for the length callback.
*
* A function pointer matching this signature may be passed to
* FLAC__stream_decoder_init*_stream(). The supplied function will be
* called when the decoder wants to know the total length of the stream
* in bytes.
*
* Here is an example of a length callback for stdio streams:
* \code
* FLAC__StreamDecoderLengthStatus length_cb(const FLAC__StreamDecoder *decoder, FLAC__uint64 *stream_length, void *client_data)
* {
* FILE *file = ((MyClientData*)client_data)->file;
* struct stat filestats;
*
* if(file == stdin)
* return FLAC__STREAM_DECODER_LENGTH_STATUS_UNSUPPORTED;
* else if(fstat(fileno(file), &filestats) != 0)
* return FLAC__STREAM_DECODER_LENGTH_STATUS_ERROR;
* else {
* *stream_length = (FLAC__uint64)filestats.st_size;
* return FLAC__STREAM_DECODER_LENGTH_STATUS_OK;
* }
* }
* \endcode
*
* \note In general, FLAC__StreamDecoder functions which change the
* state should not be called on the \a decoder while in the callback.
*
* \param decoder The decoder instance calling the callback.
* \param stream_length A pointer to storage for the length of the stream
* in bytes.
* \param client_data The callee's client data set through
* FLAC__stream_decoder_init_*().
* \retval FLAC__StreamDecoderLengthStatus
* The callee's return status.
*/
typedef FLAC__StreamDecoderLengthStatus (*FLAC__StreamDecoderLengthCallback)(const FLAC__StreamDecoder *decoder, FLAC__uint64 *stream_length, void *client_data);
/** Signature for the EOF callback.
*
* A function pointer matching this signature may be passed to
* FLAC__stream_decoder_init*_stream(). The supplied function will be
* called when the decoder needs to know if the end of the stream has
* been reached.
*
* Here is an example of a EOF callback for stdio streams:
* FLAC__bool eof_cb(const FLAC__StreamDecoder *decoder, void *client_data)
* \code
* {
* FILE *file = ((MyClientData*)client_data)->file;
* return feof(file)? true : false;
* }
* \endcode
*
* \note In general, FLAC__StreamDecoder functions which change the
* state should not be called on the \a decoder while in the callback.
*
* \param decoder The decoder instance calling the callback.
* \param client_data The callee's client data set through
* FLAC__stream_decoder_init_*().
* \retval FLAC__bool
* \c true if the currently at the end of the stream, else \c false.
*/
typedef FLAC__bool (*FLAC__StreamDecoderEofCallback)(const FLAC__StreamDecoder *decoder, void *client_data);
/** Signature for the write callback.
*
* A function pointer matching this signature must be passed to one of
* the FLAC__stream_decoder_init_*() functions.
* The supplied function will be called when the decoder has decoded a
* single audio frame. The decoder will pass the frame metadata as well
* as an array of pointers (one for each channel) pointing to the
* decoded audio.
*
* \note In general, FLAC__StreamDecoder functions which change the
* state should not be called on the \a decoder while in the callback.
*
* \param decoder The decoder instance calling the callback.
* \param frame The description of the decoded frame. See
* FLAC__Frame.
* \param buffer An array of pointers to decoded channels of data.
* Each pointer will point to an array of signed
* samples of length \a frame->header.blocksize.
* Channels will be ordered according to the FLAC
* specification; see the documentation for the
* <A HREF="../format.html#frame_header">frame header</A>.
* \param client_data The callee's client data set through
* FLAC__stream_decoder_init_*().
* \retval FLAC__StreamDecoderWriteStatus
* The callee's return status.
*/
typedef FLAC__StreamDecoderWriteStatus (*FLAC__StreamDecoderWriteCallback)(const FLAC__StreamDecoder *decoder, const FLAC__Frame *frame, const FLAC__int32 * const buffer[], void *client_data);
/** Signature for the metadata callback.
*
* A function pointer matching this signature must be passed to one of
* the FLAC__stream_decoder_init_*() functions.
* The supplied function will be called when the decoder has decoded a
* metadata block. In a valid FLAC file there will always be one
* \c STREAMINFO block, followed by zero or more other metadata blocks.
* These will be supplied by the decoder in the same order as they
* appear in the stream and always before the first audio frame (i.e.
* write callback). The metadata block that is passed in must not be
* modified, and it doesn't live beyond the callback, so you should make
* a copy of it with FLAC__metadata_object_clone() if you will need it
* elsewhere. Since metadata blocks can potentially be large, by
* default the decoder only calls the metadata callback for the
* \c STREAMINFO block; you can instruct the decoder to pass or filter
* other blocks with FLAC__stream_decoder_set_metadata_*() calls.
*
* \note In general, FLAC__StreamDecoder functions which change the
* state should not be called on the \a decoder while in the callback.
*
* \param decoder The decoder instance calling the callback.
* \param metadata The decoded metadata block.
* \param client_data The callee's client data set through
* FLAC__stream_decoder_init_*().
*/
typedef void (*FLAC__StreamDecoderMetadataCallback)(const FLAC__StreamDecoder *decoder, const FLAC__StreamMetadata *metadata, void *client_data);
/** Signature for the error callback.
*
* A function pointer matching this signature must be passed to one of
* the FLAC__stream_decoder_init_*() functions.
* The supplied function will be called whenever an error occurs during
* decoding.
*
* \note In general, FLAC__StreamDecoder functions which change the
* state should not be called on the \a decoder while in the callback.
*
* \param decoder The decoder instance calling the callback.
* \param status The error encountered by the decoder.
* \param client_data The callee's client data set through
* FLAC__stream_decoder_init_*().
*/
typedef void (*FLAC__StreamDecoderErrorCallback)(const FLAC__StreamDecoder *decoder, FLAC__StreamDecoderErrorStatus status, void *client_data);

复制代码

那么到最后，我来总结一下解码器的写法：

1、取得解码器对象。FLAC__StreamDecoder *pDecoder=FLAC__stream_decoder_new();
2、初始化解码器。用以下的几个函数中的一个来完成。其实就是告诉libFLAC，要解码的数据的来源，以及解码得到的数据的去向。
FLAC__stream_decoder_init_stream
FLAC__stream_decoder_init_ogg_stream
FLAC__stream_decoder_init_FILE
FLAC__stream_decoder_init_ogg_FILE
FLAC__stream_decoder_init_file
FLAC__stream_decoder_init_ogg_file

3、开始解码过程。调用以下的函数来实现。
FLAC__stream_decoder_process_single:解码一个块。
FLAC__stream_decoder_process_until_end_of_metadata:解码全部metadata块。
FLAC__stream_decoder_process_until_end_of_stream:解码全部块。

4、完成解码后清理用过的内存。
FLAC__stream_decoder_delete(pDecoder);

就这些。

界限突破 · 发表于 2015-4-13 18:18:34

求大神编译一个1.3.1版本的，这玩意编译真是太蛋疼了

界限突破 · 发表于 2015-4-13 18:26:43

我试了下，不知为什么链接错误一大堆，我在国外网站找的也一样

0xAA55 · 发表于 2015-4-13 19:20:37

界限突破发表于 2015-4-13 18:26
我试了下，不知为什么链接错误一大堆，我在国外网站找的也一样

你用的是libFLAC的C艹库。你需要自己构建这个子类，然后完成那些接口，否则无法链接。

界限突破 · 发表于 2015-4-13 22:46:42

0xAA55 发表于 2015-4-13 19:20
你用的是libFLAC的C艹库。你需要自己构建这个子类，然后完成那些接口，否则无法链接。 ...

soga，多谢指点

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【C】libFLAC的使用

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