PeerStreamer

/*

 * DVD subtitle encoding for ffmpeg

 * Copyright (c) 2005 Wolfram Gloger.

 *

 * This library 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 of the License, or (at your option) any later version.

 *

 * This library 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 this library; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

#include "avcodec.h"

#undef NDEBUG

#include <assert.h>

typedef struct DVDSubtitleContext {

} DVDSubtitleContext;

// ncnt is the nibble counter

#define PUTNIBBLE(val)\

do {\

    if (ncnt++ & 1)\

        *q++ = bitbuf | ((val) & 0x0f);\

    else\

        bitbuf = (val) << 4;\

} while(0)

static void dvd_encode_rle(uint8_t **pq,

                           const uint8_t *bitmap, int linesize,

                           int w, int h,

                           const int cmap[256])

{

    uint8_t *q;

    unsigned int bitbuf = 0;

    int ncnt;

    int x, y, len, color;

    q = *pq;

    for (y = 0; y < h; ++y) {

        ncnt = 0;

        for(x = 0; x < w; x += len) {

            color = bitmap[x];

            for (len=1; x+len < w; ++len)

                if (bitmap[x+len] != color)

                    break;

            color = cmap[color];

            assert(color < 4);

            if (len < 0x04) {

                PUTNIBBLE((len << 2)|color);

            } else if (len < 0x10) {

                PUTNIBBLE(len >> 2);

                PUTNIBBLE((len << 2)|color);

            } else if (len < 0x40) {

                PUTNIBBLE(0);

                PUTNIBBLE(len >> 2);

                PUTNIBBLE((len << 2)|color);

            } else if (x+len == w) {

                PUTNIBBLE(0);

                PUTNIBBLE(0);

                PUTNIBBLE(0);

                PUTNIBBLE(color);

            } else {

                if (len > 0xff)

                    len = 0xff;

                PUTNIBBLE(0);

                PUTNIBBLE(len >> 6);

                PUTNIBBLE(len >> 2);

                PUTNIBBLE((len << 2)|color);

            }

        }

        /* end of line */

        if (ncnt & 1)

            PUTNIBBLE(0);

        bitmap += linesize;

    }

    *pq = q;

}

static inline void putbe16(uint8_t **pq, uint16_t v)

{

    uint8_t *q = *pq;

    *q++ = v >> 8;

    *q++ = v;

    *pq = q;

}

static int encode_dvd_subtitles(uint8_t *outbuf, int outbuf_size,

                                const AVSubtitle *h)

{

    uint8_t *q, *qq;

    int object_id;

    int offset1[20], offset2[20];

    int i, imax, color, alpha, rects = h->num_rects;

    unsigned long hmax;

    unsigned long hist[256];

    int           cmap[256];

    if (rects == 0 || h->rects == NULL)

        return -1;

    if (rects > 20)

        rects = 20;

    // analyze bitmaps, compress to 4 colors

    for (i=0; i<256; ++i) {

        hist[i] = 0;

        cmap[i] = 0;

    }

    for (object_id = 0; object_id < rects; object_id++)

        for (i=0; i<h->rects[object_id].w*h->rects[object_id].h; ++i) {

            color = h->rects[object_id].bitmap[i];

            // only count non-transparent pixels

            alpha = h->rects[object_id].rgba_palette[color] >> 24;

            hist[color] += alpha;

        }

    for (color=3;; --color) {

        hmax = 0;

        imax = 0;

        for (i=0; i<256; ++i)

            if (hist[i] > hmax) {

                imax = i;

                hmax = hist[i];

            }

        if (hmax == 0)

            break;

        if (color == 0)

            color = 3;

        av_log(NULL, AV_LOG_DEBUG, "dvd_subtitle hist[%d]=%ld -> col %d\n",

               imax, hist[imax], color);

        cmap[imax] = color;

        hist[imax] = 0;

    }

    // encode data block

    q = outbuf + 4;

    for (object_id = 0; object_id < rects; object_id++) {

        offset1[object_id] = q - outbuf;

        // worst case memory requirement: 1 nibble per pixel..

        if ((q - outbuf) + h->rects[object_id].w*h->rects[object_id].h/2

            + 17*rects + 21 > outbuf_size) {

            av_log(NULL, AV_LOG_ERROR, "dvd_subtitle too big\n");

            return -1;

        }

        dvd_encode_rle(&q, h->rects[object_id].bitmap,

                       h->rects[object_id].w*2,

                       h->rects[object_id].w, h->rects[object_id].h >> 1,

                       cmap);

        offset2[object_id] = q - outbuf;

        dvd_encode_rle(&q, h->rects[object_id].bitmap + h->rects[object_id].w,

                       h->rects[object_id].w*2,

                       h->rects[object_id].w, h->rects[object_id].h >> 1,

                       cmap);

    }

    // set data packet size

    qq = outbuf + 2;

    putbe16(&qq, q - outbuf);

    // send start display command

    putbe16(&q, (h->start_display_time*90) >> 10);

    putbe16(&q, (q - outbuf) /*- 2 */ + 8 + 12*rects + 2);

    *q++ = 0x03; // palette - 4 nibbles

    *q++ = 0x03; *q++ = 0x7f;

    *q++ = 0x04; // alpha - 4 nibbles

    *q++ = 0xf0; *q++ = 0x00;

    //*q++ = 0x0f; *q++ = 0xff;

    // XXX not sure if more than one rect can really be encoded..

    // 12 bytes per rect

    for (object_id = 0; object_id < rects; object_id++) {

        int x2 = h->rects[object_id].x + h->rects[object_id].w - 1;

        int y2 = h->rects[object_id].y + h->rects[object_id].h - 1;

        *q++ = 0x05;

        // x1 x2 -> 6 nibbles

        *q++ = h->rects[object_id].x >> 4;

        *q++ = (h->rects[object_id].x << 4) | ((x2 >> 8) & 0xf);

        *q++ = x2;

        // y1 y2 -> 6 nibbles

        *q++ = h->rects[object_id].y >> 4;

        *q++ = (h->rects[object_id].y << 4) | ((y2 >> 8) & 0xf);

        *q++ = y2;

        *q++ = 0x06;

        // offset1, offset2

        putbe16(&q, offset1[object_id]);

        putbe16(&q, offset2[object_id]);

    }

    *q++ = 0x01; // start command

    *q++ = 0xff; // terminating command

    // send stop display command last

    putbe16(&q, (h->end_display_time*90) >> 10);

    putbe16(&q, (q - outbuf) - 2 /*+ 4*/);

    *q++ = 0x02; // set end

    *q++ = 0xff; // terminating command

    qq = outbuf;

    putbe16(&qq, q - outbuf);

    av_log(NULL, AV_LOG_DEBUG, "subtitle_packet size=%td\n", q - outbuf);

    return q - outbuf;

}

static int dvdsub_init_encoder(AVCodecContext *avctx)

{

    return 0;

}

static int dvdsub_close_encoder(AVCodecContext *avctx)

{

    return 0;

}

static int dvdsub_encode(AVCodecContext *avctx,

                         unsigned char *buf, int buf_size, void *data)

{

    //DVDSubtitleContext *s = avctx->priv_data;

    AVSubtitle *sub = data;

    int ret;

    ret = encode_dvd_subtitles(buf, buf_size, sub);

    return ret;

}

AVCodec dvdsub_encoder = {

    "dvdsub",

    CODEC_TYPE_SUBTITLE,

    CODEC_ID_DVD_SUBTITLE,

    sizeof(DVDSubtitleContext),

    dvdsub_init_encoder,

    dvdsub_encode,

    dvdsub_close_encoder,

};

/* Local Variables: */

/* c-basic-offset:4 */

/* End: */