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-rw-r--r--src/tv/vcr.c183
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diff --git a/src/tv/vcr.c b/src/tv/vcr.c
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+/* VCR test image generator
+ *
+ * (C) 2017 by Andreas Eversberg <jolly@eversberg.eu>
+ * All Rights Reserved
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <math.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include "../common/sample.h"
+#include "vcr.h"
+
+/* test ID of calibration part:
+ *
+ * 1. line: ID of 48 Bits in 52 uS
+ * 2. line: 50% Gray
+ * 3. line: 50% Gray +- 25% deviation, frequency 0 Hz
+ * 4. line: 50% Gray +- 12.5% deviation, frequency 0 Hz
+ * 5. and 6. line: as line 3 and 4, but frequnency 0.2 MHz
+ * each next two lines as above, but increments frequency by 0.2
+ * 63. and 64. line: the incement reaches 6 MHz
+ */
+#define TEST_ID "VHS V1"
+
+/* create cosine ramp, so that the bandwidth is not higher than 2 * width of the ramp(0..1) */
+static inline double ramp(double x)
+{
+ return 0.5 - 0.5 * cos(x * M_PI);
+}
+
+int vcr_gen_line(sample_t *sample, double x, double samplerate, sample_t *color_u, sample_t *color_v, int v_polarity, double line_start, double line_end, int line)
+{
+ double step = 1.0 / samplerate;
+ int i = 0;
+ double Y, Y2, U, V, frequency, colorphase, saturation;
+ double render_end, n, width;
+ int b;
+
+ /* skip x to line_start */
+ while (x < line_start && x < line_end) {
+ i++;
+ x += step;
+ }
+ if (x >= line_end)
+ return i;
+
+ /* select test pattern */
+ switch (line / 32) {
+ case 0:
+ case 1:
+ /* frequency test
+ *
+ * show frequencies from 0.5 MHz to 3.5 MHz */
+ frequency = (double)(line & 63) / 63.0 * 3000000.0 + 500000.0;
+ while (x < line_end) {
+ Y = 1.0 - (line_end - x) / (line_end - line_start);
+ sample[i++] = 0.5 + Y * 0.5 * sin(x * frequency * 2 * M_PI);
+ x += step;
+ }
+ break;
+ case 2:
+ /* level test
+ *
+ * show levels from 0 to 100% luminance */
+ Y = (double)(line & 31) / 31.0;
+ while (x < line_end) {
+ sample[i++] = Y;
+ x += step;
+ }
+ break;
+ case 3:
+ /* edge test
+ *
+ * show edges with 0.5 MHz to 3.5 MHz frequency */
+ for (n = 0.0; n < 0.99; n += 0.1) {
+ frequency = (double)(line & 31) / 31.0 * 3000000.0 + 500000.0;
+ width = 1.0 / frequency / 2.0; /* half wave length */
+ /* low level before ramping up */
+ Y = 0.5 - (n + 0.1) / 2.0;
+ Y2 = 1.0 - Y;
+ render_end = line_start + (line_end - line_start) / 40.0 * (40.0 * n + 1) - width / 2.0;
+ while (x < render_end) {
+ sample[i++] = Y;
+ x += step;
+ }
+ /* ramp up */
+ render_end += width;
+ while (x < render_end) {
+ sample[i++] = ramp((render_end - x) / width) * (Y - Y2) + Y2;
+ x += step;
+ }
+ /* high level before ramping down */
+ render_end = line_start + (line_end - line_start) / 40.0 * (40.0 * n + 3) - width / 2.0;
+ while (x < render_end) {
+ sample[i++] = Y2;
+ x += step;
+ }
+ /* ramp down */
+ render_end += width;
+ while (x < render_end) {
+ sample[i++] = ramp((render_end - x) / width) * (Y2 - Y) + Y;
+ x += step;
+ }
+ /* low level after ramping down */
+ render_end = line_start + (line_end - line_start) / 40.0 * (40.0 * n + 4);
+ while (x < render_end) {
+ sample[i++] = Y;
+ x += step;
+ }
+ }
+ break;
+ case 4:
+ case 5:
+ /* color test
+ *
+ * show color from 0 to 100% saturation */
+ Y = (1.0 - 5.0 / 7.0) * 0.75;
+ saturation = (double)(line & 63) / 63.0;
+ if (v_polarity < 0)
+ colorphase = (360.0 - 103.5) / 180.0 * M_PI;
+ else
+ colorphase = 103.5 / 180.0 * M_PI;
+ U = cos(colorphase) * saturation * 0.474 / 2.0;
+ V = sin(colorphase) * saturation * 0.474 / 2.0;
+ while (x < line_end) {
+ sample[i++] = Y;
+ color_u[i] = U;
+ color_v[i] = V;
+ x += step;
+ }
+ break;
+ case 6:
+ case 7:
+ /* calibration signal
+ *
+ * this signal is used to calibrate the frequency response of the de-emphasis
+ */
+ if ((line & 63) == 0) {
+ /* generate identification line to be detected by the decoder */
+ for (b = 0; b < 48; b++) {
+ render_end = line_start + (line_end - line_start) / 48.0 * (double)(b + 1);
+ Y = (TEST_ID[b / 8] >> (b & 7)) & 1;
+ while (x < render_end) {
+ sample[i++] = Y;
+ x += step;
+ }
+ }
+ } else if ((line & 63) == 1) {
+ /* generate zero level (50% brightness) */
+ while (x < line_end) {
+ sample[i++] = 0.5;
+ x += step;
+ }
+ } else {
+ /* each pair of lines: upper uses 50% deviation, lower uses 25% deviation */
+ if ((line & 1) == 0)
+ Y = 0.5;
+ else
+ Y = 0.25;
+ /* frequency from 0 - 6 MHz in 31 steps (each 0.2 MHz) */
+ frequency = (double)(((line & 63) - 2) / 2) * 200000.0;
+ while (x < line_end) {
+ sample[i++] = 0.5 + Y * 0.5 * cos(x * frequency * 2 * M_PI);
+ x += step;
+ }
+ }
+ }
+
+ return i;
+}