Add implementation of analog TV signal generator (PAL so far)
Quick and dirty Howto: make && tv/osmotv --sdr-soapy --sdr-tx-gain 60 -r 15000000 -c 21 tx-fubk --sdr-tune-args "OFFSET=-3000000"
This commit is contained in:
Andreas Eversberg
183
src/tv/vcr.c
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183
src/tv/vcr.c
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/* VCR test image generator
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*
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* (C) 2017 by Andreas Eversberg <jolly@eversberg.eu>
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* All Rights Reserved
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <math.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include "../common/sample.h"
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#include "vcr.h"
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/* test ID of calibration part:
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*
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* 1. line: ID of 48 Bits in 52 uS
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* 2. line: 50% Gray
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* 3. line: 50% Gray +- 25% deviation, frequency 0 Hz
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* 4. line: 50% Gray +- 12.5% deviation, frequency 0 Hz
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* 5. and 6. line: as line 3 and 4, but frequnency 0.2 MHz
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* each next two lines as above, but increments frequency by 0.2
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* 63. and 64. line: the incement reaches 6 MHz
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*/
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#define TEST_ID "VHS V1"
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/* create cosine ramp, so that the bandwidth is not higher than 2 * width of the ramp(0..1) */
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static inline double ramp(double x)
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{
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return 0.5 - 0.5 * cos(x * M_PI);
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}
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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)
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{
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double step = 1.0 / samplerate;
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int i = 0;
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double Y, Y2, U, V, frequency, colorphase, saturation;
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double render_end, n, width;
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int b;
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/* skip x to line_start */
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while (x < line_start && x < line_end) {
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i++;
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x += step;
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}
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if (x >= line_end)
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return i;
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/* select test pattern */
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switch (line / 32) {
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case 0:
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case 1:
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/* frequency test
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*
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* show frequencies from 0.5 MHz to 3.5 MHz */
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frequency = (double)(line & 63) / 63.0 * 3000000.0 + 500000.0;
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while (x < line_end) {
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Y = 1.0 - (line_end - x) / (line_end - line_start);
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sample[i++] = 0.5 + Y * 0.5 * sin(x * frequency * 2 * M_PI);
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x += step;
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}
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break;
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case 2:
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/* level test
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*
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* show levels from 0 to 100% luminance */
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Y = (double)(line & 31) / 31.0;
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while (x < line_end) {
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sample[i++] = Y;
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x += step;
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}
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break;
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case 3:
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/* edge test
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*
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* show edges with 0.5 MHz to 3.5 MHz frequency */
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for (n = 0.0; n < 0.99; n += 0.1) {
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frequency = (double)(line & 31) / 31.0 * 3000000.0 + 500000.0;
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width = 1.0 / frequency / 2.0; /* half wave length */
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/* low level before ramping up */
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Y = 0.5 - (n + 0.1) / 2.0;
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Y2 = 1.0 - Y;
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render_end = line_start + (line_end - line_start) / 40.0 * (40.0 * n + 1) - width / 2.0;
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while (x < render_end) {
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sample[i++] = Y;
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x += step;
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}
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/* ramp up */
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render_end += width;
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while (x < render_end) {
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sample[i++] = ramp((render_end - x) / width) * (Y - Y2) + Y2;
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x += step;
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}
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/* high level before ramping down */
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render_end = line_start + (line_end - line_start) / 40.0 * (40.0 * n + 3) - width / 2.0;
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while (x < render_end) {
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sample[i++] = Y2;
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x += step;
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}
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/* ramp down */
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render_end += width;
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while (x < render_end) {
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sample[i++] = ramp((render_end - x) / width) * (Y2 - Y) + Y;
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x += step;
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}
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/* low level after ramping down */
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render_end = line_start + (line_end - line_start) / 40.0 * (40.0 * n + 4);
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while (x < render_end) {
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sample[i++] = Y;
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x += step;
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}
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}
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break;
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case 4:
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case 5:
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/* color test
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*
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* show color from 0 to 100% saturation */
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Y = (1.0 - 5.0 / 7.0) * 0.75;
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saturation = (double)(line & 63) / 63.0;
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if (v_polarity < 0)
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colorphase = (360.0 - 103.5) / 180.0 * M_PI;
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else
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colorphase = 103.5 / 180.0 * M_PI;
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U = cos(colorphase) * saturation * 0.474 / 2.0;
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V = sin(colorphase) * saturation * 0.474 / 2.0;
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while (x < line_end) {
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sample[i++] = Y;
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color_u[i] = U;
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color_v[i] = V;
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x += step;
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}
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break;
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case 6:
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case 7:
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/* calibration signal
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*
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* this signal is used to calibrate the frequency response of the de-emphasis
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*/
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if ((line & 63) == 0) {
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/* generate identification line to be detected by the decoder */
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for (b = 0; b < 48; b++) {
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render_end = line_start + (line_end - line_start) / 48.0 * (double)(b + 1);
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Y = (TEST_ID[b / 8] >> (b & 7)) & 1;
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while (x < render_end) {
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sample[i++] = Y;
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x += step;
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}
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}
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} else if ((line & 63) == 1) {
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/* generate zero level (50% brightness) */
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while (x < line_end) {
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sample[i++] = 0.5;
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x += step;
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}
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} else {
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/* each pair of lines: upper uses 50% deviation, lower uses 25% deviation */
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if ((line & 1) == 0)
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Y = 0.5;
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else
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Y = 0.25;
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/* frequency from 0 - 6 MHz in 31 steps (each 0.2 MHz) */
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frequency = (double)(((line & 63) - 2) / 2) * 200000.0;
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while (x < line_end) {
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sample[i++] = 0.5 + Y * 0.5 * cos(x * frequency * 2 * M_PI);
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x += step;
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}
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}
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}
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return i;
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}
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