大侠救命！！！请帮忙看一下这个G711的程序为什么不成功

fanged

代码很简单，就是将输入的wav文件用g711压缩一下，输出成文件，然后再把压缩的文件还原成wav文件。

ifdef ENC，如果有ENC这个宏定义，就是压缩程序，如果没有，就是还原程序。我这边还原出来的老是不能正常播放，请高手指点一下，真的太谢谢了。

#include <cctype>
#include <memory>

void mulaw_dec (char *mulaw_data /* contains size char */ ,
                char *s16_data /* contains size*2 char */ ,
                int size);
void mulaw_enc (char *s16_data /* contains 320 char */ ,
                char *mulaw_data /* contains 160 char */ ,
                int pcm_size);
void alaw_dec (char *alaw_data /* contains size char */ ,
               char *s16_data /* contains size*2 char */ ,
               int size);
void alaw_enc (char *s16_data /* contains 320 char */ ,
               char *alaw_data /* contains 160 char */ ,
               int pcm_size);

//#define ENC

int main(int argc, char* argv[])
{
        printf("Hello World!\n";

        char data_out[1000];
        char data_out_enc[1000];

        memset(data_out, 0, 1000);
        memset(data_out_enc, 0, 1000);
#ifdef ENC
        FILE *f1 = fopen("toy.wav", "rb";
        FILE *f2 = fopen("enc", "wb";
#else
        FILE *f1 = fopen("enc", "rb";
        FILE *f2 = fopen("enc.wav", "wb";
#endif
        if(f1 == NULL || f2 == NULL)
        {
                return 0;       
        }
        int read = 1;
        while(read)
        {
#ifdef ENC
                read = fread(data_out, 1, 160, f1);
                mulaw_enc (data_out, data_out_enc, read);
                fwrite(data_out_enc, 1, read/2, f2);
#else
                read = fread(data_out, 1, 160, f1);
                mulaw_dec(data_out, data_out_enc, read);
                fwrite(data_out_enc, 1, read*2, f2);
#endif
        }
       
        fclose(f1);
        fclose(f2);

        printf("end\n";
        return 0;
}

/*
*  PCM - A-Law conversion
*  Copyright (c) 2000 by Abramo Bagnara <abramo@alsa-project.org>
*
*  Wrapper for linphone Codec class by Simon Morlat <simon.morlat@free.fr>
*/

int
val_seg (int val)
{
  int r = 0;

  val >>= 7;
  if (val & 0xf0)
    {
      val >>= 4;
      r += 4;
    }
  if (val & 0x0c)
    {
      val >>= 2;
      r += 2;
    }
  if (val & 0x02)
    r += 1;
  return r;
}

/*
* alaw_to_s16() - Convert an A-law value to 16-bit linear PCM
*
*/
int
alaw_to_s16 (unsigned char a_val)
{
  int t;
  int seg;

  a_val ^= 0x55;
  t = a_val & 0x7f;
  if (t < 16)
    t = (t << 4) + 8;
  else
    {
      seg = (t >> 4) & 0x07;
      t = ((t & 0x0f) << 4) + 0x108;
      t <<= seg - 1;
    }
  return ((a_val & 0x80) ? t : -t);
}

/*
* s16_to_ulaw() - Convert a linear PCM value to u-law
*
* In order to simplify the encoding process, the original linear magnitude
* is biased by adding 33 which shifts the encoding range from (0 - 815 to
* (33 - 8191). The result can be seen in the following encoding table:
*
*        Biased Linear Input Code        Compressed Code
*        ------------------------        ---------------
*        00000001wxyza                        000wxyz
*        0000001wxyzab                        001wxyz
*        000001wxyzabc                        010wxyz
*        00001wxyzabcd                        011wxyz
*        0001wxyzabcde                        100wxyz
*        001wxyzabcdef                        101wxyz
*        01wxyzabcdefg                        110wxyz
*        1wxyzabcdefgh                        111wxyz
*
* Each biased linear code has a leading 1 which identifies the segment
* number. The value of the segment number is equal to 7 minus the number
* of leading 0's. The quantization interval is directly available as the
* four bits wxyz.  * The trailing bits (a - h) are ignored.
*
* Ordinarily the complement of the resulting code word is used for
* transmission, and so the code word is complemented before it is returned.
*
* For further information see John C. Bellamy's Digital Telephony, 1982,
* John Wiley & Sons, pps 98-111 and 472-476.
*/

unsigned char
s16_to_ulaw (int pcm_val)       /* 2's complement (16-bit range) */
{
  int mask;
  int seg;
  unsigned char uval;

  if (pcm_val < 0)
    {
      pcm_val = 0x84 - pcm_val;
      mask = 0x7f;
  } else
    {
      pcm_val += 0x84;
      mask = 0xff;
    }
  if (pcm_val > 0x7fff)
    pcm_val = 0x7fff;

  /* Convert the scaled magnitude to segment number. */
  seg = val_seg (pcm_val);

  /*
   * Combine the sign, segment, quantization bits;
   * and complement the code word.
   */
  uval = (seg << 4) | ((pcm_val >> (seg + 3)) & 0x0f);
  return uval ^ mask;
}

/*
* s16_to_alaw() - Convert a 16-bit linear PCM value to 8-bit A-law
*
* s16_to_alaw() accepts an 16-bit integer and encodes it as A-law data.
*
*                Linear Input Code        Compressed Code
*        ------------------------        ---------------
*        0000000wxyza                        000wxyz
*        0000001wxyza                        001wxyz
*        000001wxyzab                        010wxyz
*        00001wxyzabc                        011wxyz
*        0001wxyzabcd                        100wxyz
*        001wxyzabcde                        101wxyz
*        01wxyzabcdef                        110wxyz
*        1wxyzabcdefg                        111wxyz
*
* For further information see John C. Bellamy's Digital Telephony, 1982,
* John Wiley & Sons, pps 98-111 and 472-476.
*/

unsigned char
s16_to_alaw (int pcm_val)
{
  int mask;
  int seg;
  unsigned char aval;

  if (pcm_val >= 0)
    {
      mask = 0xD5;
  } else
    {
      mask = 0x55;
      pcm_val = -pcm_val;
      if (pcm_val > 0x7fff)
        pcm_val = 0x7fff;
    }

  if (pcm_val < 256)
    aval = pcm_val >> 4;
  else
    {
      /* Convert the scaled magnitude to segment number. */
      seg = val_seg (pcm_val);
      aval = (seg << 4) | ((pcm_val >> (seg + 3)) & 0x0f);
    }
  return aval ^ mask;
}

/*
* ulaw_to_s16() - Convert a u-law value to 16-bit linear PCM
*
* First, a biased linear code is derived from the code word. An unbiased
* output can then be obtained by subtracting 33 from the biased code.
*
* Note that this function expects to be passed the complement of the
* original code word. This is in keeping with ISDN conventions.
*/
int
ulaw_to_s16 (unsigned char u_val)
{
  int t;

  /* Complement to obtain normal u-law value. */
  u_val = ~u_val;

  /*
   * Extract and bias the quantization bits. Then
   * shift up by the segment number and subtract out the bias.
   */
  t = ((u_val & 0x0f) << 3) + 0x84;
  t <<= (u_val & 0x70) >> 4;

  return ((u_val & 0x80) ? (0x84 - t) : (t - 0x84));
}


void
alaw_dec (char *alaw_data /* contains size char */ ,
          char *s16_data /* contains size*2 char */ ,
          int size)
{
  int i;

  for (i = 0; i < size; i++)
    {
      ((signed short *) s16_data) = alaw_to_s16 ((unsigned char) alaw_data);
    }
}

void
alaw_enc (char *s16_data /* contains 320 char */ ,
          char *alaw_data /* contains 160 char */ ,
          int pcm_size)
{
  int i;
  int limit = pcm_size / 2;

  for (i = 0; i < limit; i++)
    {
      alaw_data = s16_to_alaw (*((signed short *) s16_data));
      s16_data += 2;
    }
}

void
mulaw_dec (char *mulaw_data /* contains size char */ ,
           char *s16_data /* contains size*2 char */ ,
           int size)
{
  int i;

  for (i = 0; i < size; i++)
    {
      *((signed short *) s16_data) = ulaw_to_s16 ((unsigned char) mulaw_data);
      s16_data += 2;
    }
}

void
mulaw_enc (char *s16_data /* contains pcm_size char */ ,
           char *mulaw_data /* contains pcm_size/2 char */ ,
           int pcm_size)
{
  int i;
  int limit = pcm_size / 2;

  for (i = 0; i < limit; i++)
    {
      mulaw_data = s16_to_ulaw (*((signed short *) s16_data));
      s16_data += 2;
    }
}

vafls_scott

程序太长，没兴趣慢慢看。
你对比过原来的wav文件和还原出来的wav文件么？如果你的编解码算法没有问题的话，那可以对比一下试试。
wav文件的头有一些文件信息的数据，写的是这个wav文件的一些属性，而不是实际的波形数据。用类似mediaPlayer之类的程序播放，要先读这个头。我怀疑是这个头经过编码再解码之后，变掉了。对于波形来说，一点变化无所谓不影响播放，但如果头的数据变了的话，会认不出来。

vafls_scott

还有，你的wav文件是什么格式的？你这个g711的编解码，应该是针对8k 16位的wav文件的

borinds

wav有44字节的头，读写时要处理的。你处理没有？