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TAV: fix - TAD audio incorrectly decoding due to incorrect step size reconstruction

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minjaesong
2025-10-30 22:02:57 +09:00
parent 991d035bcc
commit c61bf7750f
2 changed files with 22 additions and 21 deletions
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23
video_encoder/decoder_tad.c
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@@ -313,24 +313,25 @@ static void dwt_dd4_inverse_1d(float *data, int length) {
}
static void dwt_inverse_multilevel(float *data, int length, int levels) {
// Calculate the length at the deepest level (size of low-pass after all forward DWTs)
int current_length = length;
for (int level = 0; level < levels; level++) {
current_length = (current_length + 1) / 2;
// Pre-calculate all intermediate lengths used during forward transform
// Forward uses: data[0..length-1], then data[0..(length+1)/2-1], etc.
int *lengths = malloc((levels + 1) * sizeof(int));
lengths[0] = length;
for (int i = 1; i <= levels; i++) {
lengths[i] = (lengths[i - 1] + 1) / 2;
}
// For 8 levels on 32768: 32768→16384→8192→4096→2048→1024→512→256→128
// Inverse transform: double size FIRST, then apply inverse DWT
// Level 8 inverse: 128 low + 128 high → 256 reconstructed
// Level 7 inverse: 256 reconstructed + 256 high → 512 reconstructed
// ... Level 1 inverse: 16384 reconstructed + 16384 high → 32768 reconstructed
// Inverse transform: apply inverse DWT using exact forward lengths in reverse order
// Forward applied DWT with lengths: [length, (length+1)/2, ((length+1)/2+1)/2, ...]
// Inverse must use same lengths in reverse: [..., ((length+1)/2+1)/2, (length+1)/2, length]
for (int level = levels - 1; level >= 0; level--) {
current_length *= 2; // MULTIPLY FIRST: 128→256, 256→512, ..., 16384→32768
if (current_length > length) current_length = length;
int current_length = lengths[level];
// dwt_haar_inverse_1d(data, current_length); // THEN apply inverse
// dwt_dd4_inverse_1d(data, current_length); // THEN apply inverse
dwt_97_inverse_1d(data, current_length); // THEN apply inverse
}
free(lengths);
}
//=============================================================================