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Merge pull request #1294 from luckytyphlosion/aif2pcm-fix

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Fix bug in pcm delta compression.
This commit is contained in:
luckytyphlosion 2021-01-26 15:23:11 -05:00 committed by GitHub
commit 740c0a6bc1
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1 changed files with 25 additions and 2 deletions
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27
tools/aif2pcm/main.c
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@ -351,6 +351,12 @@ const int gDeltaEncodingTable[] = {
-64, -49, -36, -25, -16, -9, -4, -1,
};
#define POSITIVE_DELTAS_START 0
#define POSITIVE_DELTAS_END 8
#define NEGATIVE_DELTAS_START 8
#define NEGATIVE_DELTAS_END 16
struct Bytes *delta_decompress(struct Bytes *delta, unsigned int expected_length)
{
struct Bytes *pcm = malloc(sizeof(struct Bytes));
@ -418,15 +424,32 @@ struct Bytes *delta_decompress(struct Bytes *delta, unsigned int expected_length
return pcm;
}
#define U8_TO_S8(value) ((value) < 128 ? (value) : (value) - 256)
#define ABS(value) ((value) >= 0 ? (value) : -(value))
int get_delta_index(uint8_t sample, uint8_t prev_sample)
{
int best_error = INT_MAX;
int best_index = -1;
int delta_table_start_index;
int delta_table_end_index;
int sample_signed = U8_TO_S8(sample);
int prev_sample_signed = U8_TO_S8(prev_sample);
for (int i = 0; i < 16; i++)
// if we're going up (or equal), only choose positive deltas
if (prev_sample_signed <= sample_signed) {
delta_table_start_index = POSITIVE_DELTAS_START;
delta_table_end_index = POSITIVE_DELTAS_END;
} else {
delta_table_start_index = NEGATIVE_DELTAS_START;
delta_table_end_index = NEGATIVE_DELTAS_END;
}
for (int i = delta_table_start_index; i < delta_table_end_index; i++)
{
uint8_t new_sample = prev_sample + gDeltaEncodingTable[i];
int error = sample > new_sample ? sample - new_sample : new_sample - sample;
int new_sample_signed = U8_TO_S8(new_sample);
int error = ABS(new_sample_signed - sample_signed);
if (error < best_error)
{