tav: coefficient dump visualiser

video_encoder/visualise_coefficients.c

@@ -0,0 +1,157 @@
+// Visualise DWT Coefficients as Image
+// Converts .bin coefficient file to PPM image with logarithmic color mapping
+// Usage: ./visualise_coefficients <input.bin> <output.ppm> <width> <height>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <math.h>
+
+// Logarithmic color mapping for coefficient visualisation
+// Zero: Black (#000000)
+// Positive: Red to Yellow (#FF0000 to #FFFF00) - logarithmic
+// Negative: Blue to Cyan (#0000FF to #00FFFF) - logarithmic
+typedef struct {
+    uint8_t r, g, b;
+} rgb_t;
+
+static rgb_t map_coefficient_to_color(int16_t coeff) {
+    rgb_t color = {0, 0, 0};
+
+    if (coeff == 0) {
+        // Zero: pure black
+        return color;
+    }
+
+    if (coeff > 0) {
+        // Positive: Red (#FF0000) to Yellow (#FFFF00)
+        // Logarithmic mapping: log2(1) = 0, log2(32767) ≈ 14.99
+        double log_val = log2((double)coeff);
+        double log_max = log2(32767.0);
+        double normalised = log_val / log_max;  // 0.0 to 1.0
+
+        color.r = 255;
+        color.g = (uint8_t)(normalised * 255.0);
+        color.b = 0;
+    } else {
+        // Negative: Blue (#0000FF) to Cyan (#00FFFF)
+        // Logarithmic mapping: log2(1) = 0, log2(32768) = 15
+        double log_val = log2((double)(-coeff));
+        double log_max = log2(32768.0);
+        double normalised = log_val / log_max;  // 0.0 to 1.0
+
+        color.r = 0;
+        color.g = (uint8_t)(normalised * 255.0);
+        color.b = 255;
+    }
+
+    return color;
+}
+
+int main(int argc, char *argv[]) {
+    if (argc != 5) {
+        printf("Usage: %s <input.bin> <output.ppm> <width> <height>\n", argv[0]);
+        printf("Example: %s frame_060.tavframe.y.bin output.ppm 560 448\n", argv[0]);
+        return 1;
+    }
+
+    const char *input_file = argv[1];
+    const char *output_file = argv[2];
+    int width = atoi(argv[3]);
+    int height = atoi(argv[4]);
+
+    if (width <= 0 || height <= 0) {
+        printf("Error: Invalid dimensions %dx%d\n", width, height);
+        return 1;
+    }
+
+    size_t expected_count = width * height;
+
+    // Load coefficient file
+    FILE *fp_in = fopen(input_file, "rb");
+    if (!fp_in) {
+        printf("Error: Cannot open %s\n", input_file);
+        return 1;
+    }
+
+    // Get file size
+    fseek(fp_in, 0, SEEK_END);
+    long file_size = ftell(fp_in);
+    fseek(fp_in, 0, SEEK_SET);
+
+    size_t coeff_count = file_size / sizeof(int16_t);
+
+    if (coeff_count != expected_count) {
+        printf("Warning: File contains %zu coefficients, expected %zu (%dx%d)\n",
+               coeff_count, expected_count, width, height);
+    }
+
+    // Allocate coefficient buffer
+    int16_t *coeffs = malloc(expected_count * sizeof(int16_t));
+    if (!coeffs) {
+        printf("Error: Memory allocation failed\n");
+        fclose(fp_in);
+        return 1;
+    }
+
+    // Read coefficients
+    size_t read_count = fread(coeffs, sizeof(int16_t), expected_count, fp_in);
+    fclose(fp_in);
+
+    if (read_count != expected_count) {
+        printf("Error: Read %zu coefficients, expected %zu\n", read_count, expected_count);
+        free(coeffs);
+        return 1;
+    }
+
+    // Analyse coefficient distribution
+    size_t zeros = 0, positives = 0, negatives = 0;
+    int16_t min_val = INT16_MAX, max_val = INT16_MIN;
+
+    for (size_t i = 0; i < expected_count; i++) {
+        if (coeffs[i] == 0) zeros++;
+        else if (coeffs[i] > 0) positives++;
+        else negatives++;
+
+        if (coeffs[i] < min_val) min_val = coeffs[i];
+        if (coeffs[i] > max_val) max_val = coeffs[i];
+    }
+
+    printf("Coefficient statistics:\n");
+    printf("  Total: %zu\n", expected_count);
+    printf("  Zeros: %zu (%.1f%%)\n", zeros, 100.0 * zeros / expected_count);
+    printf("  Positives: %zu (%.1f%%)\n", positives, 100.0 * positives / expected_count);
+    printf("  Negatives: %zu (%.1f%%)\n", negatives, 100.0 * negatives / expected_count);
+    printf("  Range: [%d, %d]\n", min_val, max_val);
+
+    // Write PPM image
+    FILE *fp_out = fopen(output_file, "wb");
+    if (!fp_out) {
+        printf("Error: Cannot create %s\n", output_file);
+        free(coeffs);
+        return 1;
+    }
+
+    // PPM header
+    fprintf(fp_out, "P6\n%d %d\n255\n", width, height);
+
+    // Write pixel data
+    for (int y = 0; y < height; y++) {
+        for (int x = 0; x < width; x++) {
+            size_t idx = y * width + x;
+            rgb_t color = map_coefficient_to_color(coeffs[idx]);
+            fwrite(&color, 3, 1, fp_out);
+        }
+    }
+
+    fclose(fp_out);
+    free(coeffs);
+
+    printf("\nWrote %dx%d image to %s\n", width, height, output_file);
+    printf("Color mapping:\n");
+    printf("  Black:  Zero coefficients\n");
+    printf("  Red→Yellow: Positive coefficients (logarithmic)\n");
+    printf("  Blue→Cyan: Negative coefficients (logarithmic)\n");
+
+    return 0;
+}