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/timecode.h"
35 #define LINE_DATA_SIZE 9
37 typedef struct ReadVitcContext {
48 uint8_t line_data[LINE_DATA_SIZE];
49 char tcbuf[AV_TIMECODE_STR_SIZE];
52 #define OFFSET(x) offsetof(ReadVitcContext, x)
53 #define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
55 static const AVOption readvitc_options[] = {
56 { "scan_max", "maximum line numbers to scan for VITC data", OFFSET(scan_max), AV_OPT_TYPE_INT, {.i64 = 45 }, -1, INT_MAX, FLAGS },
57 { "thr_b", "black color threshold", OFFSET(thr_b), AV_OPT_TYPE_DOUBLE, {.dbl = 0.2 }, 0, 1.0, FLAGS },
58 { "thr_w", "white color threshold", OFFSET(thr_w), AV_OPT_TYPE_DOUBLE, {.dbl = 0.6 }, 0, 1.0, FLAGS },
62 AVFILTER_DEFINE_CLASS(readvitc);
64 static uint8_t get_vitc_crc( uint8_t *line ) {
67 crc = 0x01 | (line[0] << 2);
68 crc ^= (line[0] >> 6) | 0x04 | (line[1] << 4);
69 crc ^= (line[1] >> 4) | 0x10 | (line[2] << 6);
70 crc ^= (line[2] >> 2) | 0x40;
72 crc ^= 0x01 | (line[4] << 2);
73 crc ^= (line[4] >> 6) | 0x04 | (line[5] << 4);
74 crc ^= (line[5] >> 4) | 0x10 | (line[6] << 6);
75 crc ^= (line[6] >> 2) | 0x40;
78 crc = (crc >> 2) | (crc << 6); // rotate byte right by two bits
82 static inline uint8_t get_pit_avg3( uint8_t *line, int i ) {
83 return ((line[i-1] + line[i] + line[i+1]) / 3);
86 static int read_vitc_line( ReadVitcContext *ctx, uint8_t *src, int line_size, int width, int height )
89 int grp_index, pit_index;
94 if (ctx->scan_max >= 0)
95 height = FFMIN(height, ctx->scan_max);
97 // scan lines for VITC data, starting from the top
98 for (y = 0; y < height; y++) {
100 memset(ctx->line_data, 0, LINE_DATA_SIZE);
103 while ((x < width) && (grp_index < 9)) {
104 // search next sync pattern
105 while ((x < width) && (scan_line[x] < ctx->threshold_white))
107 while ((x < width) && (scan_line[x] > ctx->threshold_black))
109 x = FFMAX(x - ((ctx->grp_width+10) / 20), 1); // step back a half pit
111 if ((grp_start_pos + ctx->grp_width) > width)
112 break; // not enough pixels for reading a whole pit group
113 pit_value = get_pit_avg3(scan_line, x);
114 if (pit_value < ctx->threshold_white)
115 break; // first sync bit mismatch
116 x = grp_start_pos + ((ctx->grp_width) / 10);
117 pit_value = get_pit_avg3(scan_line, x);
118 if (pit_value > ctx->threshold_black )
119 break; // second sync bit mismatch
120 for (pit_index = 0; pit_index <= 7; pit_index++) {
121 x = grp_start_pos + (((pit_index+2)*ctx->grp_width) / 10);
122 pit_value = get_pit_avg3(scan_line, x);
123 if (pit_value > ctx->threshold_gray)
124 ctx->line_data[grp_index] |= (1 << pit_index);
128 if ((grp_index == 9) && (get_vitc_crc(ctx->line_data) == ctx->line_data[8])) {
138 static unsigned bcd2uint(uint8_t high, uint8_t low)
140 if (high > 9 || low > 9)
142 return 10*high + low;
145 static char *make_vitc_tc_string(char *buf, uint8_t *line)
147 unsigned hh = bcd2uint(line[7] & 0x03, line[6] & 0x0f); // 6-bit hours
148 unsigned mm = bcd2uint(line[5] & 0x07, line[4] & 0x0f); // 7-bit minutes
149 unsigned ss = bcd2uint(line[3] & 0x07, line[2] & 0x0f); // 7-bit seconds
150 unsigned ff = bcd2uint(line[1] & 0x03, line[0] & 0x0f); // 6-bit frames
151 unsigned drop = (line[1] & 0x04); // 1-bit drop flag
152 snprintf(buf, AV_TIMECODE_STR_SIZE, "%02u:%02u:%02u%c%02u",
153 hh, mm, ss, drop ? ';' : ':', ff);
157 static av_cold int init(AVFilterContext *ctx)
159 ReadVitcContext *s = ctx->priv;
161 s->threshold_black = s->thr_b * UINT8_MAX;
162 s->threshold_white = s->thr_w * UINT8_MAX;
163 if (s->threshold_black > s->threshold_white) {
164 av_log(ctx, AV_LOG_WARNING, "Black color threshold is higher than white color threshold (%g > %g)\n",
166 return AVERROR(EINVAL);
168 s->threshold_gray = s->threshold_white - ((s->threshold_white - s->threshold_black) / 2);
169 av_log(ctx, AV_LOG_DEBUG, "threshold_black:%d threshold_white:%d threshold_gray:%d\n",
170 s->threshold_black, s->threshold_white, s->threshold_gray);
175 static int config_props(AVFilterLink *inlink)
177 AVFilterContext *ctx = inlink->dst;
178 ReadVitcContext *s = ctx->priv;
180 s->grp_width = inlink->w * 5 / 48;
181 av_log(ctx, AV_LOG_DEBUG, "w:%d h:%d grp_width:%d scan_max:%d\n",
182 inlink->w, inlink->h, s->grp_width, s->scan_max);
186 static const enum AVPixelFormat pixel_fmts[] = {
208 static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
210 AVFilterContext *ctx = inlink->dst;
211 AVFilterLink *outlink = ctx->outputs[0];
212 ReadVitcContext *s = ctx->priv;
215 found = read_vitc_line(s, frame->data[0], frame->linesize[0], inlink->w, inlink->h);
216 av_dict_set(&frame->metadata, "lavfi.readvitc.found", (found ? "1" : "0"), 0);
218 av_dict_set(&frame->metadata, "lavfi.readvitc.tc_str", make_vitc_tc_string(s->tcbuf, s->line_data), 0);
220 return ff_filter_frame(outlink, frame);
223 static const AVFilterPad inputs[] = {
226 .type = AVMEDIA_TYPE_VIDEO,
227 .filter_frame = filter_frame,
228 .config_props = config_props,
232 const AVFilter ff_vf_readvitc = {
234 .description = NULL_IF_CONFIG_SMALL("Read vertical interval timecode and write it to frame metadata."),
235 .priv_size = sizeof(ReadVitcContext),
236 .priv_class = &readvitc_class,
237 .flags = AVFILTER_FLAG_METADATA_ONLY,
238 FILTER_INPUTS(inputs),
239 FILTER_OUTPUTS(ff_video_default_filterpad),
240 FILTER_PIXFMTS_ARRAY(pixel_fmts),