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/* hacktv - Analogue video transmitter for the HackRF */
/*=======================================================================*/
/* Copyright 2018 Philip Heron <phil@sanslogic.co.uk> */
/* */
/* 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/>. */
/* -=== WSS encoder ===- */
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include "video.h"
#include "vbidata.h"
typedef struct {
const char *id;
uint8_t code;
} _wss_modes_t;
static const _wss_modes_t _wss_modes[] = {
{ "4:3", 0x08 },
{ "16:9", 0x07 },
{ "14:9-letterbox", 0x01 },
{ "16:9-letterbox", 0x04 },
{ "auto", 0xFF },
{ NULL, 0 },
};
static size_t _group_bits(uint8_t *vbi, uint8_t code, size_t offset, size_t length)
{
int i, b;
while(length--)
{
for(i = 0; i < 6; i++, offset++)
{
if(i == 3) code ^= 1;
b = 7 - (offset % 8);
vbi[offset / 8] &= ~(1 << b);
vbi[offset / 8] |= (code & 1) << b;
}
code >>= 1;
}
return(offset);
}
int wss_init(wss_t *s, vid_t *vid, char *mode)
{
int16_t level;
size_t o;
memset(s, 0, sizeof(wss_t));
/* Find the mode settings */
s->code = 0;
for(o = 0; _wss_modes[o].id != NULL; o++)
{
if(strcasecmp(mode, _wss_modes[o].id) == 0)
{
s->code = _wss_modes[o].code;
break;
}
}
if(s->code == 0)
{
fprintf(stderr, "wss: Unrecognised mode '%s'.\n", mode);
return(VID_ERROR);
}
/* Calculate the high level for the VBI data */
level = round((vid->white_level - vid->black_level) * (5.0 / 7.0));
s->vid = vid;
s->lut = vbidata_init(
320, s->vid->width,
level,
VBIDATA_FILTER_RC, 0.7
);
if(!s->lut)
{
return(VID_OUT_OF_MEMORY);
}
/* Prepare the VBI data. Start with the run-in and start code */
s->vbi[0] = 0xF8; // 11111000
s->vbi[1] = 0xE3; // 11100011
s->vbi[2] = 0x8E; // 10001110
s->vbi[3] = 0x38; // 00111000
s->vbi[4] = 0xF1; // 11110001
s->vbi[5] = 0xE0; // 11100000
s->vbi[6] = 0xF8; // 11111___
/* Group 1 (Aspect Ratio) */
o = _group_bits(s->vbi, s->code, 29 + 24, 4);
/* Group 2 (Enhanced Services) */
o = _group_bits(s->vbi, 0x00, o, 4);
/* Group 3 (Subtitles) */
o = _group_bits(s->vbi, 0x00, o, 3);
/* Group 4 (Reserved) */
o = _group_bits(s->vbi, 0x00, o, 3);
/* Calculate width of line to blank */
s->blank_width = round(s->vid->sample_rate * 42.5e-6);
return(VID_OK);
}
void wss_free(wss_t *s)
{
if(s == NULL) return;
free(s->lut);
memset(s, 0, sizeof(wss_t));
}
int wss_render(vid_t *s, void *arg, int nlines, vid_line_t **lines)
{
wss_t *w = arg;
vid_line_t *l = lines[0];
int x;
/* WSS is rendered on line 23 */
if(l->line != 23)
{
return(1);
}
if(w->code == 0xFF)
{
/* Auto mode selects between 4:3 and 16:9 based on the
* the ratio of the source frame. */
_group_bits(w->vbi, s->ratio <= (14.0 / 9.0) ? 0x08 : 0x07, 29 + 24, 4);
}
/* 42.5μs of line 23 needs to be blanked otherwise the WSS bits may
* overlap active video */
for(x = s->half_width; x < w->blank_width; x++)
{
l->output[x * 2] = s->black_level;
}
vbidata_render_nrz(w->lut, w->vbi, -55, 137, VBIDATA_MSB_FIRST, l->output, 2);
l->vbialloc = 1;
return(1);
}
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