/*
  * 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,
 };