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.
34 * @param c Fractional seconds that should be subtracted from the AVSubtitle's PTS.
36 TimedSubtitle::TimedSubtitle (AVSubtitle const & sub, double c)
38 assert (sub.rects > 0);
40 /* subtitle PTS in seconds */
41 double const packet_time = ((sub.pts / AV_TIME_BASE) + float (sub.pts % AV_TIME_BASE) / 1e6) - c;
43 /* hence start time for this sub */
44 _from = packet_time + (double (sub.start_display_time) / 1e3);
45 _to = packet_time + (double (sub.end_display_time) / 1e3);
47 if (sub.num_rects > 1) {
48 throw DecodeError ("multi-part subtitles not yet supported");
51 AVSubtitleRect const * rect = sub.rects[0];
53 if (rect->type != SUBTITLE_BITMAP) {
54 throw DecodeError ("non-bitmap subtitles not yet supported");
57 shared_ptr<Image> image (new SimpleImage (PIX_FMT_RGBA, Size (rect->w, rect->h), true));
59 /* Start of the first line in the subtitle */
60 uint8_t* sub_p = rect->pict.data[0];
61 /* sub_p looks up into a RGB palette which is here */
62 uint32_t const * palette = (uint32_t *) rect->pict.data[1];
63 /* Start of the output data */
64 uint32_t* out_p = (uint32_t *) image->data()[0];
66 for (int y = 0; y < rect->h; ++y) {
67 uint8_t* sub_line_p = sub_p;
68 uint32_t* out_line_p = out_p;
69 for (int x = 0; x < rect->w; ++x) {
70 *out_line_p++ = palette[*sub_line_p++];
72 sub_p += rect->pict.linesize[0];
73 out_p += image->stride()[0] / sizeof (uint32_t);
76 _subtitle.reset (new Subtitle (Position (rect->x, rect->y), image));
79 /** @param t Time in seconds from the start of the film */
81 TimedSubtitle::displayed_at (double t) const
83 return t >= _from && t <= _to;
86 /** Construct a subtitle, which is an image and a position.
87 * @param p Position within the (uncropped) source frame.
88 * @param i Image of the subtitle (should be RGBA).
90 Subtitle::Subtitle (Position p, shared_ptr<Image> i)
97 /** Given the area of a subtitle, work out the area it should
98 * take up when its video frame is scaled up, and it is optionally
99 * itself scaled and offset.
100 * @param target_x_scale the x scaling of the video frame that the subtitle is in.
101 * @param target_y_scale the y scaling of the video frame that the subtitle is in.
102 * @param sub_area The area of the subtitle within the original source.
103 * @param subtitle_offset y offset to apply to the subtitle position (+ve is down)
104 * in the coordinate space of the source.
105 * @param subtitle_scale scaling factor to apply to the subtitle image.
108 subtitle_transformed_area (
109 float target_x_scale, float target_y_scale,
110 Rect sub_area, int subtitle_offset, float subtitle_scale
115 sub_area.y += subtitle_offset;
117 /* We will scale the subtitle by the same amount as the video frame, and also by the additional
120 tx.width = sub_area.width * target_x_scale * subtitle_scale;
121 tx.height = sub_area.height * target_y_scale * subtitle_scale;
123 /* Then we need a corrective translation, consisting of two parts:
125 * 1. that which is the result of the scaling of the subtitle by target_x_scale and target_y_scale; this will be
126 * sub_area.x * target_x_scale and sub_area.y * target_y_scale.
128 * 2. that to shift the origin of the scale by subtitle_scale to the centre of the subtitle; this will be
129 * (width_before_subtitle_scale * (1 - subtitle_scale) / 2) and
130 * (height_before_subtitle_scale * (1 - subtitle_scale) / 2).
132 * Combining these two translations gives these expressions.
135 tx.x = target_x_scale * (sub_area.x + (sub_area.width * (1 - subtitle_scale) / 2));
136 tx.y = target_y_scale * (sub_area.y + (sub_area.height * (1 - subtitle_scale) / 2));
141 /** @return area that this subtitle takes up, in the original uncropped source's coordinate space */
143 Subtitle::area () const
145 return Rect (_position.x, _position.y, _image->size().width, _image->size().height);