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TAV: improved compression using some coefficient preprocessing

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minjaesong
2025-09-29 01:17:53 +09:00
parent 01278815c7
commit 66909537a0
5 changed files with 280 additions and 47 deletions
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89
video_encoder/encoder_tav.c
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@@ -74,6 +74,9 @@ int KEYFRAME_INTERVAL = 2; // refresh often because deltas in DWT are more visib
#define MP2_DEFAULT_PACKET_SIZE 1152
#define MAX_SUBTITLE_LENGTH 2048
const int makeDebugDump = -100; // enter a frame number
int debugDumpMade = 0;
// Subtitle structure
typedef struct subtitle_entry {
int start_frame;
@@ -954,6 +957,38 @@ static void dwt_2d_forward_flexible(float *tile_data, int width, int height, int
free(temp_col);
}
// Preprocess coefficients using significance map for better compression
static size_t preprocess_coefficients(int16_t *coeffs, int coeff_count, uint8_t *output_buffer) {
// Count non-zero coefficients
int nonzero_count = 0;
for (int i = 0; i < coeff_count; i++) {
if (coeffs[i] != 0) nonzero_count++;
}
// Create significance map (1 bit per coefficient, packed into bytes)
int map_bytes = (coeff_count + 7) / 8; // Round up to nearest byte
uint8_t *sig_map = output_buffer;
int16_t *values = (int16_t *)(output_buffer + map_bytes);
// Clear significance map
memset(sig_map, 0, map_bytes);
// Fill significance map and extract non-zero values
int value_idx = 0;
for (int i = 0; i < coeff_count; i++) {
if (coeffs[i] != 0) {
// Set bit in significance map
int byte_idx = i / 8;
int bit_idx = i % 8;
sig_map[byte_idx] |= (1 << bit_idx);
// Store the value
values[value_idx++] = coeffs[i];
}
}
return map_bytes + (nonzero_count * sizeof(int16_t));
}
// Quantisation for DWT subbands with rate control
static void quantise_dwt_coefficients(float *coeffs, int16_t *quantised, int size, int quantiser) {
@@ -1276,10 +1311,56 @@ static size_t serialise_tile_data(tav_encoder_t *enc, int tile_x, int tile_y,
printf("\n");
}*/
// Write quantised coefficients (both uniform and perceptual use same linear layout)
memcpy(buffer + offset, quantised_y, tile_size * sizeof(int16_t)); offset += tile_size * sizeof(int16_t);
memcpy(buffer + offset, quantised_co, tile_size * sizeof(int16_t)); offset += tile_size * sizeof(int16_t);
memcpy(buffer + offset, quantised_cg, tile_size * sizeof(int16_t)); offset += tile_size * sizeof(int16_t);
// Preprocess and write quantised coefficients using significance mapping for better compression
size_t y_compressed_size = preprocess_coefficients(quantised_y, tile_size, buffer + offset);
offset += y_compressed_size;
size_t co_compressed_size = preprocess_coefficients(quantised_co, tile_size, buffer + offset);
offset += co_compressed_size;
size_t cg_compressed_size = preprocess_coefficients(quantised_cg, tile_size, buffer + offset);
offset += cg_compressed_size;
// DEBUG: Dump raw DWT coefficients for frame ~60 when it's an intra-frame
if (!debugDumpMade && enc->frame_count >= makeDebugDump - 1 && enc->frame_count <= makeDebugDump + 2 &&
(mode == TAV_MODE_INTRA)) {
char filename[256];
size_t data_size = tile_size * sizeof(int16_t);
// Dump Y channel coefficients
snprintf(filename, sizeof(filename), "frame_%03d.tavframe.y.bin", enc->frame_count);
FILE *debug_fp = fopen(filename, "wb");
if (debug_fp) {
fwrite(quantised_y, 1, data_size, debug_fp);
fclose(debug_fp);
printf("DEBUG: Dumped Y coefficients to %s (%zu bytes)\n", filename, data_size);
}
// Dump Co channel coefficients
snprintf(filename, sizeof(filename), "frame_%03d.tavframe.co.bin", enc->frame_count);
debug_fp = fopen(filename, "wb");
if (debug_fp) {
fwrite(quantised_co, 1, data_size, debug_fp);
fclose(debug_fp);
printf("DEBUG: Dumped Co coefficients to %s (%zu bytes)\n", filename, data_size);
}
// Dump Cg channel coefficients
snprintf(filename, sizeof(filename), "frame_%03d.tavframe.cg.bin", enc->frame_count);
debug_fp = fopen(filename, "wb");
if (debug_fp) {
fwrite(quantised_cg, 1, data_size, debug_fp);
fclose(debug_fp);
printf("DEBUG: Dumped Cg coefficients to %s (%zu bytes)\n", filename, data_size);
}
printf("DEBUG: Frame %d - Dumped all %zu coefficient bytes per channel (total: %zu bytes)\n",
enc->frame_count, data_size, data_size * 3);
debugDumpMade = 1;
}
// OPTIMISATION: No need to free - using pre-allocated reusable buffers