xsubenc.c 7.14 KB
Newer Older
1 2 3 4 5
/*
 * DivX (XSUB) subtitle encoder
 * Copyright (c) 2005 DivX, Inc.
 * Copyright (c) 2009 Bjorn Axelsson
 *
6
 * This file is part of Libav.
7
 *
8
 * Libav is free software; you can redistribute it and/or
9 10 11 12
 * 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.
 *
13
 * Libav is distributed in the hope that it will be useful,
14 15 16 17 18
 * 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
19
 * License along with Libav; if not, write to the Free Software
20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "avcodec.h"
#include "bytestream.h"
#include "put_bits.h"

/**
 * Number of pixels to pad left and right.
 *
 * The official encoder pads the subtitles with two pixels on either side,
 * but until we find out why, we won't do it (we will pad to have width
 * divisible by 2 though).
 */
#define PADDING 0
#define PADDING_COLOR 0

/**
38
 * Encode a single color run. At most 16 bits will be used.
39 40
 * @param len   length of the run, values > 255 mean "until end of line", may not be < 0.
 * @param color color to encode, only the lowest two bits are used and all others must be 0.
41 42 43 44 45 46 47 48 49 50 51
 */
static void put_xsub_rle(PutBitContext *pb, int len, int color)
{
    if (len <= 255)
        put_bits(pb, 2 + ((ff_log2_tab[len] >> 1) << 2), len);
    else
        put_bits(pb, 14, 0);
    put_bits(pb, 2, color);
}

/**
52
 * Encode a 4-color bitmap with XSUB rle.
53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92
 *
 * The encoded bitmap may be wider than the source bitmap due to padding.
 */
static int xsub_encode_rle(PutBitContext *pb, const uint8_t *bitmap,
                           int linesize, int w, int h)
{
    int x0, x1, y, len, color = PADDING_COLOR;

    for (y = 0; y < h; y++) {
        x0 = 0;
        while (x0 < w) {
            // Make sure we have enough room for at least one run and padding
            if (pb->size_in_bits - put_bits_count(pb) < 7*8)
                return -1;

            x1 = x0;
            color = bitmap[x1++] & 3;
            while (x1 < w && (bitmap[x1] & 3) == color)
                x1++;
            len = x1 - x0;
            if (PADDING && x0 == 0) {
                if (color == PADDING_COLOR) {
                    len += PADDING;
                    x0  -= PADDING;
                } else
                    put_xsub_rle(pb, PADDING, PADDING_COLOR);
            }

            // Run can't be longer than 255, unless it is the rest of a row
            if (x1 == w && color == PADDING_COLOR) {
                len += PADDING + (w&1);
            } else
                len = FFMIN(len, 255);
            put_xsub_rle(pb, len, color);

            x0 += len;
        }
        if (color != PADDING_COLOR && (PADDING + (w&1)))
            put_xsub_rle(pb, PADDING + (w&1), PADDING_COLOR);

93
        avpriv_align_put_bits(pb);
94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113

        bitmap += linesize;
    }

    return 0;
}

static int make_tc(uint64_t ms, int *tc)
{
    static const int tc_divs[3] = { 1000, 60, 60 };
    int i;
    for (i=0; i<3; i++) {
        tc[i] = ms % tc_divs[i];
        ms /= tc_divs[i];
    }
    tc[3] = ms;
    return ms > 99;
}

static int xsub_encode(AVCodecContext *avctx, unsigned char *buf,
114
                       int bufsize, const AVSubtitle *h)
115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155
{
    uint64_t startTime = h->pts / 1000; // FIXME: need better solution...
    uint64_t endTime = startTime + h->end_display_time - h->start_display_time;
    int start_tc[4], end_tc[4];
    uint8_t *hdr = buf + 27; // Point behind the timestamp
    uint8_t *rlelenptr;
    uint16_t width, height;
    int i;
    PutBitContext pb;

    if (bufsize < 27 + 7*2 + 4*3) {
        av_log(avctx, AV_LOG_ERROR, "Buffer too small for XSUB header.\n");
        return -1;
    }

    // TODO: support multiple rects
    if (h->num_rects > 1)
        av_log(avctx, AV_LOG_WARNING, "Only single rects supported (%d in subtitle.)\n", h->num_rects);

    // TODO: render text-based subtitles into bitmaps
    if (!h->rects[0]->pict.data[0] || !h->rects[0]->pict.data[1]) {
        av_log(avctx, AV_LOG_WARNING, "No subtitle bitmap available.\n");
        return -1;
    }

    // TODO: color reduction, similar to dvdsub encoder
    if (h->rects[0]->nb_colors > 4)
        av_log(avctx, AV_LOG_WARNING, "No more than 4 subtitle colors supported (%d found.)\n", h->rects[0]->nb_colors);

    // TODO: Palette swapping if color zero is not transparent
    if (((uint32_t *)h->rects[0]->pict.data[1])[0] & 0xff)
        av_log(avctx, AV_LOG_WARNING, "Color index 0 is not transparent. Transparency will be messed up.\n");

    if (make_tc(startTime, start_tc) || make_tc(endTime, end_tc)) {
        av_log(avctx, AV_LOG_WARNING, "Time code >= 100 hours.\n");
        return -1;
    }

    snprintf(buf, 28,
        "[%02d:%02d:%02d.%03d-%02d:%02d:%02d.%03d]",
        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]);
157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195

    // Width and height must probably be multiples of 2.
    // 2 pixels required on either side of subtitle.
    // Possibly due to limitations of hardware renderers.
    // TODO: check if the bitmap is already padded
    width  = FFALIGN(h->rects[0]->w, 2) + PADDING * 2;
    height = FFALIGN(h->rects[0]->h, 2);

    bytestream_put_le16(&hdr, width);
    bytestream_put_le16(&hdr, height);
    bytestream_put_le16(&hdr, h->rects[0]->x);
    bytestream_put_le16(&hdr, h->rects[0]->y);
    bytestream_put_le16(&hdr, h->rects[0]->x + width);
    bytestream_put_le16(&hdr, h->rects[0]->y + height);

    rlelenptr = hdr; // Will store length of first field here later.
    hdr+=2;

    // Palette
    for (i=0; i<4; i++)
        bytestream_put_be24(&hdr, ((uint32_t *)h->rects[0]->pict.data[1])[i]);

    // Bitmap
    // RLE buffer. Reserve 2 bytes for possible padding after the last row.
    init_put_bits(&pb, hdr, bufsize - (hdr - buf) - 2);
    if (xsub_encode_rle(&pb, h->rects[0]->pict.data[0],
                        h->rects[0]->pict.linesize[0]*2,
                        h->rects[0]->w, (h->rects[0]->h + 1) >> 1))
        return -1;
    bytestream_put_le16(&rlelenptr, put_bits_count(&pb) >> 3); // Length of first field

    if (xsub_encode_rle(&pb, h->rects[0]->pict.data[0] + h->rects[0]->pict.linesize[0],
                        h->rects[0]->pict.linesize[0]*2,
                        h->rects[0]->w, h->rects[0]->h >> 1))
        return -1;

    // Enforce total height to be be multiple of 2
    if (h->rects[0]->h & 1) {
        put_xsub_rle(&pb, h->rects[0]->w, PADDING_COLOR);
196
        avpriv_align_put_bits(&pb);
197 198 199 200 201 202 203 204 205 206 207 208 209 210 211
    }

    flush_put_bits(&pb);

    return hdr - buf + put_bits_count(&pb)/8;
}

static av_cold int xsub_encoder_init(AVCodecContext *avctx)
{
    if (!avctx->codec_tag)
        avctx->codec_tag = MKTAG('D','X','S','B');

    return 0;
}

212
AVCodec ff_xsub_encoder = {
Anton Khirnov's avatar
Anton Khirnov committed
213 214 215 216 217 218
    .name       = "xsub",
    .type       = AVMEDIA_TYPE_SUBTITLE,
    .id         = AV_CODEC_ID_XSUB,
    .init       = xsub_encoder_init,
    .encode_sub = xsub_encode,
    .long_name  = NULL_IF_CONFIG_SMALL("DivX subtitles (XSUB)"),
219
};