2 Copyright (C) 2012 Carl Hetherington <cth@carlh.net>
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 2 of the License, or
7 (at your option) any later version.
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
14 You should have received a copy of the GNU General Public License
15 along with this program; if not, write to the Free Software
16 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
20 /** @file src/subtitle.cc
21 * @brief Representations of subtitles.
26 #include "exceptions.h"
29 using namespace boost;
31 /** Construct a TimedSubtitle. This is a subtitle image, position,
32 * and a range of time over which it should be shown.
33 * @param sub AVSubtitle to read.
35 TimedSubtitle::TimedSubtitle (AVSubtitle const & sub)
37 assert (sub.num_rects > 0);
39 /* Subtitle PTS in seconds (within the source, not taking into account any of the
40 source that we may have chopped off for the DCP)
42 double const packet_time = static_cast<double> (sub.pts) / AV_TIME_BASE;
44 /* hence start time for this sub */
45 _from = packet_time + (double (sub.start_display_time) / 1e3);
46 _to = packet_time + (double (sub.end_display_time) / 1e3);
48 if (sub.num_rects > 1) {
49 throw DecodeError ("multi-part subtitles not yet supported");
52 AVSubtitleRect const * rect = sub.rects[0];
54 if (rect->type != SUBTITLE_BITMAP) {
55 throw DecodeError ("non-bitmap subtitles not yet supported");
58 shared_ptr<Image> image (new SimpleImage (PIX_FMT_RGBA, libdcp::Size (rect->w, rect->h), true));
60 /* Start of the first line in the subtitle */
61 uint8_t* sub_p = rect->pict.data[0];
62 /* sub_p looks up into a RGB palette which is here */
63 uint32_t const * palette = (uint32_t *) rect->pict.data[1];
64 /* Start of the output data */
65 uint32_t* out_p = (uint32_t *) image->data()[0];
67 for (int y = 0; y < rect->h; ++y) {
68 uint8_t* sub_line_p = sub_p;
69 uint32_t* out_line_p = out_p;
70 for (int x = 0; x < rect->w; ++x) {
71 *out_line_p++ = palette[*sub_line_p++];
73 sub_p += rect->pict.linesize[0];
74 out_p += image->stride()[0] / sizeof (uint32_t);
77 _subtitle.reset (new Subtitle (Position (rect->x, rect->y), image));
80 /** @param t Time in seconds from the start of the source */
82 TimedSubtitle::displayed_at (double t) const
84 return t >= _from && t <= _to;
87 /** Construct a subtitle, which is an image and a position.
88 * @param p Position within the (uncropped) source frame.
89 * @param i Image of the subtitle (should be RGBA).
91 Subtitle::Subtitle (Position p, shared_ptr<Image> i)
98 /** Given the area of a subtitle, work out the area it should
99 * take up when its video frame is scaled up, and it is optionally
100 * itself scaled and offset.
101 * @param target_x_scale the x scaling of the video frame that the subtitle is in.
102 * @param target_y_scale the y scaling of the video frame that the subtitle is in.
103 * @param sub_area The area of the subtitle within the original source.
104 * @param subtitle_offset y offset to apply to the subtitle position (+ve is down)
105 * in the coordinate space of the source.
106 * @param subtitle_scale scaling factor to apply to the subtitle image.
109 subtitle_transformed_area (
110 float target_x_scale, float target_y_scale,
111 Rect sub_area, int subtitle_offset, float subtitle_scale
116 sub_area.y += subtitle_offset;
118 /* We will scale the subtitle by the same amount as the video frame, and also by the additional
121 tx.width = sub_area.width * target_x_scale * subtitle_scale;
122 tx.height = sub_area.height * target_y_scale * subtitle_scale;
124 /* Then we need a corrective translation, consisting of two parts:
126 * 1. that which is the result of the scaling of the subtitle by target_x_scale and target_y_scale; this will be
127 * sub_area.x * target_x_scale and sub_area.y * target_y_scale.
129 * 2. that to shift the origin of the scale by subtitle_scale to the centre of the subtitle; this will be
130 * (width_before_subtitle_scale * (1 - subtitle_scale) / 2) and
131 * (height_before_subtitle_scale * (1 - subtitle_scale) / 2).
133 * Combining these two translations gives these expressions.
136 tx.x = target_x_scale * (sub_area.x + (sub_area.width * (1 - subtitle_scale) / 2));
137 tx.y = target_y_scale * (sub_area.y + (sub_area.height * (1 - subtitle_scale) / 2));
142 /** @return area that this subtitle takes up, in the original uncropped source's coordinate space */
144 Subtitle::area () const
146 return Rect (_position.x, _position.y, _image->size().width, _image->size().height);