[Speex-dev] Encode/Decode problem

[Jean-Marc Valin]

Hi,

If you're looking at only one frame, I can understand why you don't get
the same thing. In narrowband more, Speex introduces a 80-sample delay,
not to mention that the decoded signal is supposed to _sound_ the same,
not necessarily _look_ the same.

	Jean-Marc

Le vendredi 12 août 2005 à 10:05 -0500, James Stanton a écrit :
> I'm trying to use the speex API, and I think I'm missing something.  I'm 
> running on Mac OSX Tiger, and the attached microphone is a iSight.  If I 
> call the "speex_encode_int" function, and then immediately call the 
> "speex_decode_int" function, shouldn't I get back the same data?  i.e. 
> in my example code, shouldn't the two arrays contain at least similar 
> data?  The data I'm seeing is drastically different.  If so, is the 
> encoding data sensitive?  If my data being fed in is wrong, will the 
> encoding and decoding not work correctly?    Any help would be greatly 
> appriciated.
> 
> Thanks!
> 
> Jamie Stanton
> jstanton at clairvista.com
> 
> I've got the following code:
> 
> static void testAudio(UInt8 *data, long dataLength)
> {
> //data is a linear PCM stream from an attached microphone.  sample rate 
> is 8000, 16 bits per sample
> void *state;
> void *state2;
> SpeexBits bits;
> short tempShort;
> short tempPtr[160];
> short tempPtrDecode[160];
> state = speex_encoder_init(&speex_nb_mode);
> state2 = speex_decoder_init(&speex_nb_mode);
> speex_bits_init(&bits);
> //code simplified to just read in the first frame
> for (int i = 0; i < 320; i +=2)
> {
>     tempShort = *((short*)(data + i));
>     tempPtr[i / 2] = tempShort;
> }
> speex_bits_reset(&bits);
> speex_encode_int(state, tempPtr, &bits);
> speex_bits_rewind(&bits);
> speex_decode_int(state2, &bits, tempPtrDecode);
> //tempPtr != tempPtrDecode, it's not even close.
> }
> 
> 
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> 
-- 
Jean-Marc Valin <Jean-Marc.Valin at USherbrooke.ca>
Université de Sherbrooke