1.wave文件的四个部分
1.0 四个部分
RIFF Header
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ID = 'RIFF'
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RIFF_TYPE='WAVE'
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Format Chunk
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ID = 'fmt '
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Fact Chunk 可选
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ID = 'fact'
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Data Chunk
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ID ='data'
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1.1 RIFF_WAVE_Chunk
名称
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长度
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内容
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ID
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4 Bytes
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'RIFF'
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Size
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4 Bytes
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整个文件大小-8
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Type
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4 Bytes
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'WAVE'
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1.2 Format Chunk
名称
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长度
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内容
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ID
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4 Bytes
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'fmt '
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Size
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4 Bytes
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18/16 (有无附加信息)
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本结构大小(除ID,Size)
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FormatTag
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2 Bytes
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通常0x0001
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编码方式
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Channels
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2 Bytes
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1--单声道;2--双声道立体声
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声道数目
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SamplesPerSec
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4 Bytes
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采样频率
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AvgBytesPerSec
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4 Bytes
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每秒所需字节数
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BlockAlign
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2 Bytes
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数据块对齐单位
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BitsPerSample
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2 Bytes
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每个采样需要的位bit数
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附加信息
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2 Bytes
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(可选,通过Size来判断有无)
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附加信息
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1.3 Fact_Chunk
ID
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4 Bytes
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'fact'
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Size
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4 Bytes
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数值为4
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data
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4 Bytes
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1.4 Data_Chunk
ID
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4 Bytes
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'data'
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Size
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4 Bytes
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数据区大小
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data
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4 Bytes
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数据区,真正存储数据的地方
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参考文章:
WAV文件结构
二.
2.1 读取wave文件的前45个字节,并按顺序打印出来。并作分析
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cong@msi:/work/ffmpeg/test/alsa/testalsa/1wave$ ls ../../../resource/test.wav -l
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-rw-rw-r-- 1 cong cong 39623500 Aug 17 16:35 ../../../resource/test.wav
这个文件的总长度是39623500=0x25C9B4C
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RIFF_HEADER:
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0=0x52 1=0x49 2=0x46 3=0x46 --> 'RIFF'
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4=0x44 5=0x9b 6=0x5c 7=0x02 --> size=0x025c9b44=文件的总长度-8(即这个size代表去除RIFF与本身之外的文件长度)
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8=0x57 9=0x41 10=0x56 11=0x45 --> 'WAVE'
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Format Chunk:
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12=0x66 13=0x6d 14=0x74 15=0x20 --> 'fmt'
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16=0x10 17=0x00 18=0x00 19=0x00 --> len=16=Format部分的长度是16个byte(不包括自身)
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20=0x01 21=0x00 --> FormatTag=0x0001(1代表WAV_FMT_PCM)
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22=0x02 23=0x00 --> channels=0x0002
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24=0x44 25=0xac 26=0x00 27=0x00 --> SamplePerSec=0x0000ac44=44100
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28=0x10 29=0xb1 30=0x02 31=0x00 --> AvgBytePerSec=0x0002b110=176400
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32=0x04 33=0x00 --> BlockAlign=0x0004=4
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34=0x10 35=0x00 --> BitsPerSample=0x0010=16
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Fact Chunk: none
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Data Chunk:
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36=0x64 37=0x61 38=0x74 39=0x61 -->'data'
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40=0x20 41=0x9b 42=0x5c 43=0x02 --> size=0x025c9b20=剩余的数据长度=文件总长度-RIFF-Format-Data
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44=0x00
45=0x00
46=0x00
47=0x00
48=0x00
49=0x00
50=0x00
51=0x00
52=0x00
53=0x00
54=0x00
55=0x00
56=0x00
57=0x00
58=0x00
59=0x00
2.2 关于wav与 DTS-in-WAV
下面是打印的一个DTS-in-WAV的前60个字节
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RIFF_Header:
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0=0x52 1=0x49 2=0x46 3=0x46
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4=0x24 5=0xe0 6=0xd5 7=0x02
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8=0x57 9=0x41 10=0x56 11=0x45
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Format_Chunk:
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12=0x66 13=0x6d 14=0x74 15=0x20
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16=0x10 17=0x00 18=0x00 19=0x00
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20=0x01 21=0x00
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22=0x02 23=0x00
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24=0x44 25=0xac 26=0x00 27=0x00
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28=0x10 29=0xb1 30=0x02 31=0x00
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32=0x04 33=0x00
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34=0x10 35=0x00
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Fact Chunk: none
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Data Chunk:
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36=0x64 37=0x61 38=0x74 39=0x61
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40=0x00 41=0xe0 42=0xd5 43=0x02
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44=0xff 45=0x1f 46=0x00 47=0xe8 48=0xf1 49=0x07
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50=0xdf
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51=0xfc
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52=0x98
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53=0xfc
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54=0x01
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55=0xec
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56=0xe9
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57=0xf4
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58=0x09
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59=0x00
DTS-coding有两种格式: raw bitsteam coding 与14bit words,而这两种格式进行coding时既可用big-endian也可用little-endian
所以为了区分就在每帧开头加上如下标志:
Every frame in DTS starts with 32-bit syncword which can be used to distinguish current bitstream encoding:
Sequence
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Bitstream type
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7F FE 80 01
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raw big-endian
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FE 7F 01 80
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raw little-endian
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1F FF E8 00 07 Fx
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14-bit big-endian
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FF 1F 00 E8 Fx 07
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14-bit little-endian
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所以要区分wav与DTS-in-WAV,文件头(前44个字节)是一样的没法区分,只能判断数据部分是否是以上面的4组开始。
参考:
三.
3.1 代码
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#include "utils.h"
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#include <stdlib.h>
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typedef struct {
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u_int magic; /* 'RIFF' */
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u_int length; /* filelen */
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u_int type; /* 'WAVE' */
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} WaveHeader;
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typedef struct {
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u_short format; /* see WAV_FMT_* */
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u_short channels;
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u_int sample_fq; /* frequence of sample */
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u_int byte_p_sec;
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u_short byte_p_spl; /* samplesize; 1 or 2 bytes */
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u_short bit_p_spl; /* 8, 12 or 16 bit */
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} WaveFmtBody;
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typedef struct {
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WaveFmtBody format;
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u_short ext_size;
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u_short bit_p_spl;
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u_int channel_mask;
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u_short guid_format; /* WAV_FMT_* */
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u_char guid_tag[14]; /* WAV_GUID_TAG */
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} WaveFmtExtensibleBody;
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typedef struct {
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u_int type; /* 'data' */
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u_int length; /* samplecount */
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} WaveChunkHeader;
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#define COMPOSE_ID(a,b,c,d) ((a) | ((b)<<8) | ((c)<<16) | ((d)<<24))
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#define WAV_RIFF COMPOSE_ID('R','I','F','F')
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#define WAV_WAVE COMPOSE_ID('W','A','V','E')
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#define WAV_FMT COMPOSE_ID('f','m','t',' ')
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#define WAV_DATA COMPOSE_ID('d','a','t','a')
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int check_wavfile(int fd)
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{
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int ret;
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int i, len;
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WaveHeader* header;
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WaveFmtBody* fmt;
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WaveChunkHeader* chunk_header;
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unsigned char* pbuf = (unsigned char*)malloc(128);
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if(NULL == pbuf)
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{
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dbmsg("pbuf malloc error");
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return -1;
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}
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//1. 读取wave的Header部分并解析
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len = sizeof(WaveHeader);
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if( (ret=read(fd, pbuf, len)) != len)
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{
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dbmsg("read error");
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return -1;
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}
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header = (WaveHeader*)pbuf;
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if( (header->magic!=WAV_RIFF) || (header->type!=WAV_WAVE))
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{
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dbmsg("not a wav file");
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return -1;
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}
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//2.读取wave的FormatChunk部分并解析
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//2.FormatChunk又可分为header和body两部分
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len = sizeof(WaveChunkHeader)+sizeof(WaveFmtBody);
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if( (ret=read(fd, pbuf, len)) != len)
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{
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dbmsg("read error");
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return -1;
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}
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chunk_header = (WaveChunkHeader*)pbuf;
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if( chunk_header->type!=WAV_FMT)
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{
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dbmsg("fmt body error");
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return -1;
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}
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fmt = (WaveFmtBody*)(pbuf+sizeof(WaveChunkHeader));
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if(fmt->format != 0x0001) //WAV_FMT_PCM
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{
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dbmsg("format is not pcm");
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return -1;
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}
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dbmsg("format=0x%x, channels=0x%x,sample_fq=%d,byte_p_sec=%d,byte_p_sample=%d,bit_p_sample=%d",
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fmt->format, fmt->channels,fmt->sample_fq, fmt->byte_p_sec,
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fmt->byte_p_spl, fmt->bit_p_spl);
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//3.读取wave的DataChunk部分并解析
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//3.DataChunk只包括header部分
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len = sizeof(WaveChunkHeader);
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if( (ret=read(fd, pbuf, len)) != len)
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{
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dbmsg("read error");
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return -1;
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}
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chunk_header = (WaveChunkHeader*)pbuf;
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if(chunk_header->type != WAV_DATA)
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{
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dbmsg("not data chunk");
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return -1;
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}
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dbmsg("pcm_data_size=0x%x",chunk_header->length); //这个长度就是wav文件中的纯数据的长度.
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free(pbuf);
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pbuf = NULL;
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return -1;
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}
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int main ( int argc, char *argv[] )
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{
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int fd;
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if(argc < 2)
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{
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dbmsg("usage: ./waveinfo ");
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return -1;
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}
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fd = open(argv[1], O_RDWR);
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if(fd<0)
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{
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dbmsg("open error");
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return -1;
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}
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check_wavfile(fd);
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return EXIT_SUCCESS;
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}
3.2 运行结果
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cong@msi:/work/ffmpeg/test/alsa/testalsa/1wave$ make run
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./wave /work/ffmpeg/test/resource//test.wav
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wave.c:check_wavfile[86]: format=0x1, channels=0x2,sample_fq=44100,byte_p_sec=176400,byte_p_sample=4,bit_p_sample=16
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wave.c:check_wavfile[100]: pcm_data_size=0x25c9b20
3.2 代码打包
1wave.rar(下载后改名为1wave.tar.gz)
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