2 * Copyright (c) 2016 Tobias Rapp
4 * This file is part of FFmpeg.
6 * FFmpeg is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
11 * FFmpeg is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with FFmpeg; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
23 * Filter for reading the vertical interval timecode (VITC).
24 * See also https://en.wikipedia.org/wiki/Vertical_interval_timecode
27 #include "libavutil/common.h"
28 #include "libavutil/internal.h"
29 #include "libavutil/opt.h"
30 #include "libavutil/pixdesc.h"
31 #include "libavutil/timecode.h"
36 #define LINE_DATA_SIZE 9
38 typedef struct ReadVitcContext {
49 uint8_t line_data[LINE_DATA_SIZE];
50 char tcbuf[AV_TIMECODE_STR_SIZE];
53 #define OFFSET(x) offsetof(ReadVitcContext, x)
54 #define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
56 static const AVOption readvitc_options[] = {
57 { "scan_max", "maximum line numbers to scan for VITC data", OFFSET(scan_max), AV_OPT_TYPE_INT, {.i64 = 45 }, -1, INT_MAX, FLAGS },
58 { "thr_b", "black color threshold", OFFSET(thr_b), AV_OPT_TYPE_DOUBLE, {.dbl = 0.2 }, 0, 1.0, FLAGS },
59 { "thr_w", "white color threshold", OFFSET(thr_w), AV_OPT_TYPE_DOUBLE, {.dbl = 0.6 }, 0, 1.0, FLAGS },
63 AVFILTER_DEFINE_CLASS(readvitc);
65 static uint8_t get_vitc_crc( uint8_t *line ) {
68 crc = 0x01 | (line[0] << 2);
69 crc ^= (line[0] >> 6) | 0x04 | (line[1] << 4);
70 crc ^= (line[1] >> 4) | 0x10 | (line[2] << 6);
71 crc ^= (line[2] >> 2) | 0x40;
73 crc ^= 0x01 | (line[4] << 2);
74 crc ^= (line[4] >> 6) | 0x04 | (line[5] << 4);
75 crc ^= (line[5] >> 4) | 0x10 | (line[6] << 6);
76 crc ^= (line[6] >> 2) | 0x40;
79 crc = (crc >> 2) | (crc << 6); // rotate byte right by two bits
83 static inline uint8_t get_pit_avg3( uint8_t *line, int i ) {
84 return ((line[i-1] + line[i] + line[i+1]) / 3);
87 static int read_vitc_line( ReadVitcContext *ctx, uint8_t *src, int line_size, int width, int height )
90 int grp_index, pit_index;
95 if (ctx->scan_max >= 0)
96 height = FFMIN(height, ctx->scan_max);
98 // scan lines for VITC data, starting from the top
99 for (y = 0; y < height; y++) {
101 memset(ctx->line_data, 0, LINE_DATA_SIZE);
104 while ((x < width) && (grp_index < 9)) {
105 // search next sync pattern
106 while ((x < width) && (scan_line[x] < ctx->threshold_white))
108 while ((x < width) && (scan_line[x] > ctx->threshold_black))
110 x = FFMAX(x - ((ctx->grp_width+10) / 20), 1); // step back a half pit
112 if ((grp_start_pos + ctx->grp_width) > width)
113 break; // not enough pixels for reading a whole pit group
114 pit_value = get_pit_avg3(scan_line, x);
115 if (pit_value < ctx->threshold_white)
116 break; // first sync bit mismatch
117 x = grp_start_pos + ((ctx->grp_width) / 10);
118 pit_value = get_pit_avg3(scan_line, x);
119 if (pit_value > ctx->threshold_black )
120 break; // second sync bit mismatch
121 for (pit_index = 0; pit_index <= 7; pit_index++) {
122 x = grp_start_pos + (((pit_index+2)*ctx->grp_width) / 10);
123 pit_value = get_pit_avg3(scan_line, x);
124 if (pit_value > ctx->threshold_gray)
125 ctx->line_data[grp_index] |= (1 << pit_index);
129 if ((grp_index == 9) && (get_vitc_crc(ctx->line_data) == ctx->line_data[8])) {
139 static unsigned bcd2uint(uint8_t high, uint8_t low)
141 if (high > 9 || low > 9)
143 return 10*high + low;
146 static char *make_vitc_tc_string(char *buf, uint8_t *line)
148 unsigned hh = bcd2uint(line[7] & 0x03, line[6] & 0x0f); // 6-bit hours
149 unsigned mm = bcd2uint(line[5] & 0x07, line[4] & 0x0f); // 7-bit minutes
150 unsigned ss = bcd2uint(line[3] & 0x07, line[2] & 0x0f); // 7-bit seconds
151 unsigned ff = bcd2uint(line[1] & 0x03, line[0] & 0x0f); // 6-bit frames
152 unsigned drop = (line[1] & 0x04); // 1-bit drop flag
153 snprintf(buf, AV_TIMECODE_STR_SIZE, "%02u:%02u:%02u%c%02u",
154 hh, mm, ss, drop ? ';' : ':', ff);
158 static av_cold int init(AVFilterContext *ctx)
160 ReadVitcContext *s = ctx->priv;
162 s->threshold_black = s->thr_b * UINT8_MAX;
163 s->threshold_white = s->thr_w * UINT8_MAX;
164 if (s->threshold_black > s->threshold_white) {
165 av_log(ctx, AV_LOG_WARNING, "Black color threshold is higher than white color threshold (%g > %g)\n",
167 return AVERROR(EINVAL);
169 s->threshold_gray = s->threshold_white - ((s->threshold_white - s->threshold_black) / 2);
170 av_log(ctx, AV_LOG_DEBUG, "threshold_black:%d threshold_white:%d threshold_gray:%d\n",
171 s->threshold_black, s->threshold_white, s->threshold_gray);
176 static int config_props(AVFilterLink *inlink)
178 AVFilterContext *ctx = inlink->dst;
179 ReadVitcContext *s = ctx->priv;
181 s->grp_width = inlink->w * 5 / 48;
182 av_log(ctx, AV_LOG_DEBUG, "w:%d h:%d grp_width:%d scan_max:%d\n",
183 inlink->w, inlink->h, s->grp_width, s->scan_max);
187 static int query_formats(AVFilterContext *ctx)
189 static const enum AVPixelFormat pixel_fmts[] = {
210 AVFilterFormats *fmts_list = ff_make_format_list(pixel_fmts);
212 return AVERROR(ENOMEM);
213 return ff_set_common_formats(ctx, fmts_list);
216 static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
218 AVFilterContext *ctx = inlink->dst;
219 AVFilterLink *outlink = ctx->outputs[0];
220 ReadVitcContext *s = ctx->priv;
223 found = read_vitc_line(s, frame->data[0], frame->linesize[0], inlink->w, inlink->h);
224 av_dict_set(&frame->metadata, "lavfi.readvitc.found", (found ? "1" : "0"), 0);
226 av_dict_set(&frame->metadata, "lavfi.readvitc.tc_str", make_vitc_tc_string(s->tcbuf, s->line_data), 0);
228 return ff_filter_frame(outlink, frame);
231 static const AVFilterPad inputs[] = {
234 .type = AVMEDIA_TYPE_VIDEO,
235 .filter_frame = filter_frame,
236 .config_props = config_props,
241 static const AVFilterPad outputs[] = {
244 .type = AVMEDIA_TYPE_VIDEO,
249 const AVFilter ff_vf_readvitc = {
251 .description = NULL_IF_CONFIG_SMALL("Read vertical interval timecode and write it to frame metadata."),
252 .priv_size = sizeof(ReadVitcContext),
253 .priv_class = &readvitc_class,
257 .query_formats = query_formats,