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https://github.com/webmproject/libwebp.git
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simplify the alpha-filter testing loop
Change-Id: Iacebae749c37edc87a3c94c76cd589a2565ee642
This commit is contained in:
skal
parent
0d25876bad
commit
2053c2cff2
179
src/enc/alpha.c
179
src/enc/alpha.c
@ -97,6 +97,7 @@ static int EncodeLossless(const uint8_t* const data, int width, int height,
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// -----------------------------------------------------------------------------
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// This function always returns an initialized 'bw' object, even upon error.
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static int EncodeAlphaInternal(const uint8_t* const data, int width, int height,
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int method, int filter, int reduce_levels,
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int effort_level, // in [0..6] range
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@ -175,6 +176,92 @@ static int GetNumColors(const uint8_t* data, int width, int height,
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return colors;
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}
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// Given the input 'filter' option, return an OR'd bit-set of filters to try.
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static uint32_t GetFilterMap(const uint8_t* alpha, int width, int height,
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int filter, int effort_level) {
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uint32_t bit_map = 0U;
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if (filter == WEBP_FILTER_FAST) {
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// Quick estimate of the best candidate.
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int try_filter_none = (effort_level > 3);
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const int kMinColorsForFilterNone = 16;
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const int kMaxColorsForFilterNone = 192;
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const int num_colors = GetNumColors(alpha, width, height, width);
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// For low number of colors, NONE yeilds better compression.
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filter = (num_colors <= kMinColorsForFilterNone) ? WEBP_FILTER_NONE :
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EstimateBestFilter(alpha, width, height, width);
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bit_map |= 1 << filter;
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// For large number of colors, try FILTER_NONE in addition to the best
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// filter as well.
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if (try_filter_none || num_colors > kMaxColorsForFilterNone) {
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bit_map |= 1 << WEBP_FILTER_NONE;
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}
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} else if (filter == WEBP_FILTER_NONE) {
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bit_map = 1 << WEBP_FILTER_NONE;
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} else { // WEBP_FILTER_BEST
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bit_map = (1 << WEBP_FILTER_LAST) - 1; // try all.
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}
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return bit_map;
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}
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// Small struct to hold the result of a filter mode compression attempt.
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typedef struct {
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size_t score;
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VP8BitWriter bw;
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WebPAuxStats stats;
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} FilterTrial;
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static void InitFilterTrial(FilterTrial* const score) {
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score->score = (size_t)~0U;
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VP8BitWriterInit(&score->bw, 0);
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}
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static int ApplyFilters(const uint8_t* alpha, int width, int height,
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uint64_t data_size, int method, int filter,
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int reduce_levels, int effort_level,
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uint8_t** const output, size_t* const output_size,
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WebPAuxStats* const stats) {
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int ok = 1;
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uint8_t* filtered_alpha = NULL;
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uint32_t try_map = GetFilterMap(alpha, width, height, filter, effort_level);
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filtered_alpha = (uint8_t*)malloc(data_size);
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ok = (filtered_alpha != NULL);
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if (ok) {
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FilterTrial best;
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InitFilterTrial(&best);
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for (filter = WEBP_FILTER_NONE; try_map; ++filter, try_map >>= 1) {
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if (try_map & 1) {
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FilterTrial trial;
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ok = EncodeAlphaInternal(alpha, width, height, method, filter,
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reduce_levels, effort_level, filtered_alpha,
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&trial.bw, stats);
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if (ok) {
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trial.score = VP8BitWriterSize(&trial.bw);
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if (trial.score < best.score) {
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VP8BitWriterWipeOut(&best.bw);
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best = trial;
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if (stats != NULL) best.stats = *stats;
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}
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} else {
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VP8BitWriterWipeOut(&trial.bw);
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VP8BitWriterWipeOut(&best.bw);
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break;
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}
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}
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}
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if (ok) {
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if (stats != NULL) *stats = best.stats;
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*output_size = VP8BitWriterSize(&best.bw);
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*output = VP8BitWriterBuf(&best.bw);
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}
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free(filtered_alpha);
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}
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return ok;
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}
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static int EncodeAlpha(VP8Encoder* const enc,
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int quality, int method, int filter,
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int effort_level,
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@ -223,105 +310,19 @@ static int EncodeAlpha(VP8Encoder* const enc,
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}
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if (ok) {
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VP8BitWriter bw;
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int test_filter;
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uint8_t* filtered_alpha = NULL;
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int try_filter_none = (effort_level > 3);
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if (filter == WEBP_FILTER_FAST) { // Quick estimate of the best candidate.
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const int kMinColorsForFilterNone = 16;
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const int kMaxColorsForFilterNone = 192;
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const int num_colors = GetNumColors(quant_alpha, width, height, width);
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// For low number of colors, NONE yeilds better compression.
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filter = (num_colors <= kMinColorsForFilterNone) ? WEBP_FILTER_NONE :
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EstimateBestFilter(quant_alpha, width, height, width);
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// For large number of colors, try FILTER_NONE in addition to the best
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// filter as well.
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if (num_colors > kMaxColorsForFilterNone) {
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try_filter_none = 1;
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}
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}
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// Test for WEBP_FILTER_NONE for higher effort levels.
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if (try_filter_none || filter == WEBP_FILTER_NONE) {
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ok = EncodeAlphaInternal(quant_alpha, width, height,
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method, WEBP_FILTER_NONE, reduce_levels,
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effort_level, NULL, &bw, pic->stats);
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if (!ok) {
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VP8BitWriterWipeOut(&bw);
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goto End;
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}
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}
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// Stop?
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if (filter == WEBP_FILTER_NONE) {
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goto Ok;
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}
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filtered_alpha = (uint8_t*)malloc(data_size);
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ok = (filtered_alpha != NULL);
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if (!ok) {
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goto End;
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}
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// Try the other mode(s).
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{
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WebPAuxStats best_stats;
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size_t best_score = try_filter_none ?
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VP8BitWriterSize(&bw) : (size_t)~0U;
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int wipe_tmp_bw = try_filter_none;
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memset(&best_stats, 0, sizeof(best_stats)); // prevent spurious warning
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if (pic->stats != NULL) best_stats = *pic->stats;
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for (test_filter =
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try_filter_none ? WEBP_FILTER_HORIZONTAL : WEBP_FILTER_NONE;
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ok && (test_filter <= WEBP_FILTER_GRADIENT);
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++test_filter) {
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VP8BitWriter tmp_bw;
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if (filter != WEBP_FILTER_BEST && test_filter != filter) {
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continue;
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}
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ok = EncodeAlphaInternal(quant_alpha, width, height,
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method, test_filter, reduce_levels,
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effort_level, filtered_alpha, &tmp_bw,
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ok = ApplyFilters(quant_alpha, width, height, data_size, method, filter,
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reduce_levels, effort_level, output, output_size,
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pic->stats);
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if (ok) {
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const size_t score = VP8BitWriterSize(&tmp_bw);
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if (score < best_score) {
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// swap bitwriter objects.
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VP8BitWriter tmp = tmp_bw;
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tmp_bw = bw;
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bw = tmp;
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best_score = score;
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if (pic->stats != NULL) best_stats = *pic->stats;
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}
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} else {
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VP8BitWriterWipeOut(&bw);
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}
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if (wipe_tmp_bw) {
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VP8BitWriterWipeOut(&tmp_bw);
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}
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wipe_tmp_bw = 1; // For next filter trial for WEBP_FILTER_BEST.
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}
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if (pic->stats != NULL) *pic->stats = best_stats;
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}
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Ok:
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if (ok) {
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*output_size = VP8BitWriterSize(&bw);
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*output = VP8BitWriterBuf(&bw);
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if (pic->stats != NULL) { // need stats?
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pic->stats->coded_size += (int)(*output_size);
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enc->sse_[3] = sse;
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}
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}
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free(filtered_alpha);
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}
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End:
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free(quant_alpha);
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return ok;
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}
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//------------------------------------------------------------------------------
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// Main calls
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