1/*
2 * DivX (XSUB) subtitle encoder
3 * Copyright (c) 2005 DivX, Inc.
4 * Copyright (c) 2009 Bjorn Axelsson
5 *
6 * This file is part of FFmpeg.
7 *
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
12 *
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 */
22
23#include "avcodec.h"
24#include "bytestream.h"
25#include "put_bits.h"
26
27/**
28 * Number of pixels to pad left and right.
29 *
30 * The official encoder pads the subtitles with two pixels on either side,
31 * but until we find out why, we won't do it (we will pad to have width
32 * divisible by 2 though).
33 */
34#define PADDING 0
35#define PADDING_COLOR 0
36
37/**
38 * Encode a single color run. At most 16 bits will be used.
39 * @param len   length of the run, values > 255 mean "until end of line", may not be < 0.
40 * @param color color to encode, only the lowest two bits are used and all others must be 0.
41 */
42static void put_xsub_rle(PutBitContext *pb, int len, int color)
43{
44    if (len <= 255)
45        put_bits(pb, 2 + ((ff_log2_tab[len] >> 1) << 2), len);
46    else
47        put_bits(pb, 14, 0);
48    put_bits(pb, 2, color);
49}
50
51/**
52 * Encode a 4-color bitmap with XSUB rle.
53 *
54 * The encoded bitmap may be wider than the source bitmap due to padding.
55 */
56static int xsub_encode_rle(PutBitContext *pb, const uint8_t *bitmap,
57                           int linesize, int w, int h)
58{
59    int x0, x1, y, len, color = PADDING_COLOR;
60
61    for (y = 0; y < h; y++) {
62        x0 = 0;
63        while (x0 < w) {
64            // Make sure we have enough room for at least one run and padding
65            if (pb->size_in_bits - put_bits_count(pb) < 7*8)
66                return -1;
67
68            x1 = x0;
69            color = bitmap[x1++] & 3;
70            while (x1 < w && (bitmap[x1] & 3) == color)
71                x1++;
72            len = x1 - x0;
73            if (PADDING && x0 == 0) {
74                if (color == PADDING_COLOR) {
75                    len += PADDING;
76                    x0  -= PADDING;
77                } else
78                    put_xsub_rle(pb, PADDING, PADDING_COLOR);
79            }
80
81            // Run can't be longer than 255, unless it is the rest of a row
82            if (x1 == w && color == PADDING_COLOR) {
83                len += PADDING + (w&1);
84            } else
85                len = FFMIN(len, 255);
86            put_xsub_rle(pb, len, color);
87
88            x0 += len;
89        }
90        if (color != PADDING_COLOR && (PADDING + (w&1)))
91            put_xsub_rle(pb, PADDING + (w&1), PADDING_COLOR);
92
93        avpriv_align_put_bits(pb);
94
95        bitmap += linesize;
96    }
97
98    return 0;
99}
100
101static int make_tc(uint64_t ms, int *tc)
102{
103    static const int tc_divs[3] = { 1000, 60, 60 };
104    int i;
105    for (i=0; i<3; i++) {
106        tc[i] = ms % tc_divs[i];
107        ms /= tc_divs[i];
108    }
109    tc[3] = ms;
110    return ms > 99;
111}
112
113static int xsub_encode(AVCodecContext *avctx, unsigned char *buf,
114                       int bufsize, const AVSubtitle *h)
115{
116    uint64_t startTime = h->pts / 1000; // FIXME: need better solution...
117    uint64_t endTime = startTime + h->end_display_time - h->start_display_time;
118    int start_tc[4], end_tc[4];
119    uint8_t *hdr = buf + 27; // Point behind the timestamp
120    uint8_t *rlelenptr;
121    uint16_t width, height;
122    int i;
123    PutBitContext pb;
124
125    if (bufsize < 27 + 7*2 + 4*3) {
126        av_log(avctx, AV_LOG_ERROR, "Buffer too small for XSUB header.\n");
127        return -1;
128    }
129
130    // TODO: support multiple rects
131    if (h->num_rects != 1)
132        av_log(avctx, AV_LOG_WARNING, "Only single rects supported (%d in subtitle.)\n", h->num_rects);
133
134    // TODO: render text-based subtitles into bitmaps
135    if (!h->rects[0]->pict.data[0] || !h->rects[0]->pict.data[1]) {
136        av_log(avctx, AV_LOG_WARNING, "No subtitle bitmap available.\n");
137        return -1;
138    }
139
140    // TODO: color reduction, similar to dvdsub encoder
141    if (h->rects[0]->nb_colors > 4)
142        av_log(avctx, AV_LOG_WARNING, "No more than 4 subtitle colors supported (%d found.)\n", h->rects[0]->nb_colors);
143
144    // TODO: Palette swapping if color zero is not transparent
145    if (((uint32_t *)h->rects[0]->pict.data[1])[0] & 0xff000000)
146        av_log(avctx, AV_LOG_WARNING, "Color index 0 is not transparent. Transparency will be messed up.\n");
147
148    if (make_tc(startTime, start_tc) || make_tc(endTime, end_tc)) {
149        av_log(avctx, AV_LOG_WARNING, "Time code >= 100 hours.\n");
150        return -1;
151    }
152
153    snprintf(buf, 28,
154        "[%02d:%02d:%02d.%03d-%02d:%02d:%02d.%03d]",
155        start_tc[3], start_tc[2], start_tc[1], start_tc[0],
156        end_tc[3],   end_tc[2],   end_tc[1],   end_tc[0]);
157
158    // Width and height must probably be multiples of 2.
159    // 2 pixels required on either side of subtitle.
160    // Possibly due to limitations of hardware renderers.
161    // TODO: check if the bitmap is already padded
162    width  = FFALIGN(h->rects[0]->w, 2) + PADDING * 2;
163    height = FFALIGN(h->rects[0]->h, 2);
164
165    bytestream_put_le16(&hdr, width);
166    bytestream_put_le16(&hdr, height);
167    bytestream_put_le16(&hdr, h->rects[0]->x);
168    bytestream_put_le16(&hdr, h->rects[0]->y);
169    bytestream_put_le16(&hdr, h->rects[0]->x + width -1);
170    bytestream_put_le16(&hdr, h->rects[0]->y + height -1);
171
172    rlelenptr = hdr; // Will store length of first field here later.
173    hdr+=2;
174
175    // Palette
176    for (i=0; i<4; i++)
177        bytestream_put_be24(&hdr, ((uint32_t *)h->rects[0]->pict.data[1])[i]);
178
179    // Bitmap
180    // RLE buffer. Reserve 2 bytes for possible padding after the last row.
181    init_put_bits(&pb, hdr, bufsize - (hdr - buf) - 2);
182    if (xsub_encode_rle(&pb, h->rects[0]->pict.data[0],
183                        h->rects[0]->pict.linesize[0]*2,
184                        h->rects[0]->w, (h->rects[0]->h + 1) >> 1))
185        return -1;
186    bytestream_put_le16(&rlelenptr, put_bits_count(&pb) >> 3); // Length of first field
187
188    if (xsub_encode_rle(&pb, h->rects[0]->pict.data[0] + h->rects[0]->pict.linesize[0],
189                        h->rects[0]->pict.linesize[0]*2,
190                        h->rects[0]->w, h->rects[0]->h >> 1))
191        return -1;
192
193    // Enforce total height to be a multiple of 2
194    if (h->rects[0]->h & 1) {
195        put_xsub_rle(&pb, h->rects[0]->w, PADDING_COLOR);
196        avpriv_align_put_bits(&pb);
197    }
198
199    flush_put_bits(&pb);
200
201    return hdr - buf + put_bits_count(&pb)/8;
202}
203
204static av_cold int xsub_encoder_init(AVCodecContext *avctx)
205{
206    if (!avctx->codec_tag)
207        avctx->codec_tag = MKTAG('D','X','S','B');
208
209    avctx->bits_per_coded_sample = 4;
210
211    return 0;
212}
213
214AVCodec ff_xsub_encoder = {
215    .name       = "xsub",
216    .long_name  = NULL_IF_CONFIG_SMALL("DivX subtitles (XSUB)"),
217    .type       = AVMEDIA_TYPE_SUBTITLE,
218    .id         = AV_CODEC_ID_XSUB,
219    .init       = xsub_encoder_init,
220    .encode_sub = xsub_encode,
221};
222