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FFmpeg4/libavfilter/vf_readvitc.c

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/*
* Copyright (c) 2016 Tobias Rapp
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file
* Filter for reading the vertical interval timecode (VITC).
* See also https://en.wikipedia.org/wiki/Vertical_interval_timecode
*/
#include "libavutil/common.h"
#include "libavutil/internal.h"
#include "libavutil/opt.h"
#include "libavutil/pixdesc.h"
#include "libavutil/timecode.h"
#include "avfilter.h"
#include "formats.h"
#include "internal.h"
#define LINE_DATA_SIZE 9
typedef struct ReadVitcContext {
const AVClass *class;
int scan_max;
double thr_b;
double thr_w;
int threshold_black;
int threshold_white;
int threshold_gray;
int grp_width;
uint8_t line_data[LINE_DATA_SIZE];
char tcbuf[AV_TIMECODE_STR_SIZE];
} ReadVitcContext;
#define OFFSET(x) offsetof(ReadVitcContext, x)
#define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
static const AVOption readvitc_options[] = {
{ "scan_max", "maximum line numbers to scan for VITC data", OFFSET(scan_max), AV_OPT_TYPE_INT, {.i64 = 45 }, -1, INT_MAX, FLAGS },
{ "thr_b", "black color threshold", OFFSET(thr_b), AV_OPT_TYPE_DOUBLE, {.dbl = 0.2 }, 0, 1.0, FLAGS },
{ "thr_w", "white color threshold", OFFSET(thr_w), AV_OPT_TYPE_DOUBLE, {.dbl = 0.6 }, 0, 1.0, FLAGS },
{ NULL }
};
AVFILTER_DEFINE_CLASS(readvitc);
static uint8_t get_vitc_crc( uint8_t *line ) {
uint8_t crc;
crc = 0x01 | (line[0] << 2);
crc ^= (line[0] >> 6) | 0x04 | (line[1] << 4);
crc ^= (line[1] >> 4) | 0x10 | (line[2] << 6);
crc ^= (line[2] >> 2) | 0x40;
crc ^= line[3];
crc ^= 0x01 | (line[4] << 2);
crc ^= (line[4] >> 6) | 0x04 | (line[5] << 4);
crc ^= (line[5] >> 4) | 0x10 | (line[6] << 6);
crc ^= (line[6] >> 2) | 0x40;
crc ^= line[7];
crc ^= 0x01;
crc = (crc >> 2) | (crc << 6); // rotate byte right by two bits
return crc;
}
static inline uint8_t get_pit_avg3( uint8_t *line, int i ) {
return ((line[i-1] + line[i] + line[i+1]) / 3);
}
static int read_vitc_line( ReadVitcContext *ctx, uint8_t *src, int line_size, int width, int height )
{
uint8_t *scan_line;
int grp_index, pit_index;
int grp_start_pos;
uint8_t pit_value;
int x, y, res = 0;
if (ctx->scan_max >= 0)
height = FFMIN(height, ctx->scan_max);
// scan lines for VITC data, starting from the top
for (y = 0; y < height; y++) {
scan_line = src;
memset(ctx->line_data, 0, LINE_DATA_SIZE);
grp_index = 0;
x = 0;
while ((x < width) && (grp_index < 9)) {
// search next sync pattern
while ((x < width) && (scan_line[x] < ctx->threshold_white))
x++;
while ((x < width) && (scan_line[x] > ctx->threshold_black))
x++;
x = FFMAX(x - ((ctx->grp_width+10) / 20), 1); // step back a half pit
grp_start_pos = x;
if ((grp_start_pos + ctx->grp_width) > width)
break; // not enough pixels for reading a whole pit group
pit_value = get_pit_avg3(scan_line, x);
if (pit_value < ctx->threshold_white)
break; // first sync bit mismatch
x = grp_start_pos + ((ctx->grp_width) / 10);
pit_value = get_pit_avg3(scan_line, x);
if (pit_value > ctx->threshold_black )
break; // second sync bit mismatch
for (pit_index = 0; pit_index <= 7; pit_index++) {
x = grp_start_pos + (((pit_index+2)*ctx->grp_width) / 10);
pit_value = get_pit_avg3(scan_line, x);
if (pit_value > ctx->threshold_gray)
ctx->line_data[grp_index] |= (1 << pit_index);
}
grp_index++;
}
if ((grp_index == 9) && (get_vitc_crc(ctx->line_data) == ctx->line_data[8])) {
res = 1;
break;
}
src += line_size;
}
return res;
}
static unsigned bcd2uint(uint8_t high, uint8_t low)
{
if (high > 9 || low > 9)
return 0;
return 10*high + low;
}
static char *make_vitc_tc_string(char *buf, uint8_t *line)
{
unsigned hh = bcd2uint(line[7] & 0x03, line[6] & 0x0f); // 6-bit hours
unsigned mm = bcd2uint(line[5] & 0x07, line[4] & 0x0f); // 7-bit minutes
unsigned ss = bcd2uint(line[3] & 0x07, line[2] & 0x0f); // 7-bit seconds
unsigned ff = bcd2uint(line[1] & 0x03, line[0] & 0x0f); // 6-bit frames
unsigned drop = (line[1] & 0x04); // 1-bit drop flag
snprintf(buf, AV_TIMECODE_STR_SIZE, "%02u:%02u:%02u%c%02u",
hh, mm, ss, drop ? ';' : ':', ff);
return buf;
}
static av_cold int init(AVFilterContext *ctx)
{
ReadVitcContext *s = ctx->priv;
s->threshold_black = s->thr_b * UINT8_MAX;
s->threshold_white = s->thr_w * UINT8_MAX;
if (s->threshold_black > s->threshold_white) {
av_log(ctx, AV_LOG_WARNING, "Black color threshold is higher than white color threshold (%g > %g)\n",
s->thr_b, s->thr_w);
return AVERROR(EINVAL);
}
s->threshold_gray = s->threshold_white - ((s->threshold_white - s->threshold_black) / 2);
av_log(ctx, AV_LOG_DEBUG, "threshold_black:%d threshold_white:%d threshold_gray:%d\n",
s->threshold_black, s->threshold_white, s->threshold_gray);
return 0;
}
static int config_props(AVFilterLink *inlink)
{
AVFilterContext *ctx = inlink->dst;
ReadVitcContext *s = ctx->priv;
s->grp_width = inlink->w * 5 / 48;
av_log(ctx, AV_LOG_DEBUG, "w:%d h:%d grp_width:%d scan_max:%d\n",
inlink->w, inlink->h, s->grp_width, s->scan_max);
return 0;
}
static int query_formats(AVFilterContext *ctx)
{
static const enum AVPixelFormat pixel_fmts[] = {
AV_PIX_FMT_GRAY8,
AV_PIX_FMT_NV12,
AV_PIX_FMT_NV16,
AV_PIX_FMT_NV21,
AV_PIX_FMT_YUV410P,
AV_PIX_FMT_YUV411P,
AV_PIX_FMT_YUV420P,
AV_PIX_FMT_YUV422P,
AV_PIX_FMT_YUV440P,
AV_PIX_FMT_YUV444P,
AV_PIX_FMT_YUVA420P,
AV_PIX_FMT_YUVA422P,
AV_PIX_FMT_YUVA444P,
AV_PIX_FMT_YUVJ411P,
AV_PIX_FMT_YUVJ420P,
AV_PIX_FMT_YUVJ422P,
AV_PIX_FMT_YUVJ440P,
AV_PIX_FMT_YUVJ444P,
AV_PIX_FMT_NONE
};
AVFilterFormats *fmts_list = ff_make_format_list(pixel_fmts);
if (!fmts_list)
return AVERROR(ENOMEM);
return ff_set_common_formats(ctx, fmts_list);
}
static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
{
AVFilterContext *ctx = inlink->dst;
AVFilterLink *outlink = ctx->outputs[0];
ReadVitcContext *s = ctx->priv;
int found;
found = read_vitc_line(s, frame->data[0], frame->linesize[0], inlink->w, inlink->h);
av_dict_set(&frame->metadata, "lavfi.readvitc.found", (found ? "1" : "0"), 0);
if (found)
av_dict_set(&frame->metadata, "lavfi.readvitc.tc_str", make_vitc_tc_string(s->tcbuf, s->line_data), 0);
return ff_filter_frame(outlink, frame);
}
static const AVFilterPad inputs[] = {
{
.name = "default",
.type = AVMEDIA_TYPE_VIDEO,
.filter_frame = filter_frame,
.config_props = config_props,
},
{ NULL }
};
static const AVFilterPad outputs[] = {
{
.name = "default",
.type = AVMEDIA_TYPE_VIDEO,
},
{ NULL }
};
AVFilter ff_vf_readvitc = {
.name = "readvitc",
.description = NULL_IF_CONFIG_SMALL("Read vertical interval timecode and write it to frame metadata."),
.priv_size = sizeof(ReadVitcContext),
.priv_class = &readvitc_class,
.inputs = inputs,
.outputs = outputs,
.init = init,
.query_formats = query_formats,
};
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