Speex解碼的幀不是原始幀

Question

我需要您的幫助來確定下面的示例代碼（從speex手冊中獲取）用於固定點編碼的問題。 我測試了160個樣本幀的編碼，然後將其解碼回來。但問題是，解碼後的幀與原始幀完全不同（請參閱下面的註釋輸出內容）。這是什麼原因？感謝您的任何幫助

#include<stdio.h> 
#include"intel16.h" 
#include <speex/speex.h> 
#define FRAME_SIZE 160 
#define MAX_NB_BYTES 25 

SpeexBits bits; 
void *enc_state; 
int quality=4;  
int nbBytes; 

int byte_ptr; 

int frame_size; 

short frame[FRAME_SIZE]; 

char outBuffer[20]; 
SpeexBits decBits; 

void *dec_state; 

short decFrame[FRAME_SIZE]; 

int z=0; 

int frame_size; 

int main (int argc,char **argv) 
{ 
for(z=0;z<160;z++) 
    { 
    frame[z]=intel_theme[z]; //array of short from "intel16" header file 
    } 
printf("\n =================================== \n"); 

for(z=0;z<160;z++) 
    { 
     printf("%i",frame[z]); 
    printf (" "); 
     } 
    speex_bits_init(&bits); 

    enc_state = speex_encoder_init(&speex_nb_mode); 



    speex_encoder_ctl(enc_state,SPEEX_GET_FRAME_SIZE,&frame_size); 

    speex_encoder_ctl(enc_state,SPEEX_SET_QUALITY,&quality); 

    speex_bits_reset(&bits); 

     speex_encode_int(enc_state, frame, &bits);  
      // encoding from frame to &bits 
    nbBytes = speex_bits_write(&bits, outBuffer, MAX_NB_BYTES); 
     //writing from &bits to outBuffer 
//----------------------------------------------------  
    speex_bits_destroy(&bits); 

    speex_encoder_destroy(enc_state); 

    printf("\n outBuffer: "); 

     for(z=0;z<20;z++) 
    { 
    printf("%c",outBuffer[z]); 
    } 
    printf("\n \n"); 

//-----------DECODING------------------- 
speex_bits_init(&decBits); 
dec_state=speex_decoder_init(&speex_nb_mode); 
speex_decoder_ctl(dec_state, SPEEX_GET_FRAME_SIZE, &frame_size); 


speex_bits_read_from(&decBits,outBuffer,nbBytes); 
speex_decode_int(dec_state,&decBits,decFrame); 
//---------------------------------------------------- 
printf("\n BUFFER DECODED BACK \n"); 

for(z=0;z<160;z++) 
{ 
printf("%i",decFrame[z]); 
printf (" "); 
} 

speex_bits_destroy(&decBits); 
speex_decoder_destroy(dec_state); 
/*==========END OF DECODING==============*/ 
printf("\n nbBytes: "); 
printf("%i",nbBytes); 
printf("\n frame_size= "); 
printf("%i",frame_size); 
printf ("\n"); 
//----------------- 
printf("end of run!"); 

return 0; 
} 

Answer 1

Speex是一個有損編解碼器。這意味着解碼器的輸出通常會與編碼器的輸入有所不同。由於Speex允許稍微改變數據，它可以更多地壓縮數據。

http://www.speex.org/docs/manual/speex-manual/node4.html#SECTION00413000000000000000