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ffmpeg / libavcodec / dvdsubenc.c @ 2912e87a

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/*
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 * DVD subtitle encoding for ffmpeg
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 * Copyright (c) 2005 Wolfram Gloger
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 *
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 * This file is part of Libav.
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 *
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 * Libav is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * Libav is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with Libav; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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#include "avcodec.h"
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#include "bytestream.h"
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#undef NDEBUG
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#include <assert.h>
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// ncnt is the nibble counter
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#define PUTNIBBLE(val)\
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do {\
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    if (ncnt++ & 1)\
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        *q++ = bitbuf | ((val) & 0x0f);\
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    else\
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        bitbuf = (val) << 4;\
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} while(0)
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static void dvd_encode_rle(uint8_t **pq,
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                           const uint8_t *bitmap, int linesize,
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                           int w, int h,
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                           const int cmap[256])
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{
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    uint8_t *q;
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    unsigned int bitbuf = 0;
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    int ncnt;
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    int x, y, len, color;
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    q = *pq;
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    for (y = 0; y < h; ++y) {
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        ncnt = 0;
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        for(x = 0; x < w; x += len) {
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            color = bitmap[x];
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            for (len=1; x+len < w; ++len)
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                if (bitmap[x+len] != color)
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                    break;
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            color = cmap[color];
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            assert(color < 4);
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            if (len < 0x04) {
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                PUTNIBBLE((len << 2)|color);
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            } else if (len < 0x10) {
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                PUTNIBBLE(len >> 2);
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                PUTNIBBLE((len << 2)|color);
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            } else if (len < 0x40) {
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                PUTNIBBLE(0);
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                PUTNIBBLE(len >> 2);
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                PUTNIBBLE((len << 2)|color);
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            } else if (x+len == w) {
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                PUTNIBBLE(0);
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                PUTNIBBLE(0);
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                PUTNIBBLE(0);
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                PUTNIBBLE(color);
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            } else {
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                if (len > 0xff)
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                    len = 0xff;
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                PUTNIBBLE(0);
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                PUTNIBBLE(len >> 6);
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                PUTNIBBLE(len >> 2);
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                PUTNIBBLE((len << 2)|color);
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            }
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        }
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        /* end of line */
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        if (ncnt & 1)
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            PUTNIBBLE(0);
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        bitmap += linesize;
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    }
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    *pq = q;
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}
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static int encode_dvd_subtitles(uint8_t *outbuf, int outbuf_size,
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                                const AVSubtitle *h)
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{
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    uint8_t *q, *qq;
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    int object_id;
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    int offset1[20], offset2[20];
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    int i, imax, color, alpha, rects = h->num_rects;
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    unsigned long hmax;
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    unsigned long hist[256];
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    int           cmap[256];
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    if (rects == 0 || h->rects == NULL)
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        return -1;
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    if (rects > 20)
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        rects = 20;
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    // analyze bitmaps, compress to 4 colors
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    for (i=0; i<256; ++i) {
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        hist[i] = 0;
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        cmap[i] = 0;
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    }
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    for (object_id = 0; object_id < rects; object_id++)
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        for (i=0; i<h->rects[object_id]->w*h->rects[object_id]->h; ++i) {
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            color = h->rects[object_id]->pict.data[0][i];
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            // only count non-transparent pixels
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            alpha = ((uint32_t*)h->rects[object_id]->pict.data[1])[color] >> 24;
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            hist[color] += alpha;
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        }
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    for (color=3;; --color) {
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        hmax = 0;
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        imax = 0;
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        for (i=0; i<256; ++i)
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            if (hist[i] > hmax) {
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                imax = i;
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                hmax = hist[i];
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            }
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        if (hmax == 0)
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            break;
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        if (color == 0)
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            color = 3;
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        av_log(NULL, AV_LOG_DEBUG, "dvd_subtitle hist[%d]=%ld -> col %d\n",
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               imax, hist[imax], color);
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        cmap[imax] = color;
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        hist[imax] = 0;
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    }
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    // encode data block
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    q = outbuf + 4;
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    for (object_id = 0; object_id < rects; object_id++) {
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        offset1[object_id] = q - outbuf;
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        // worst case memory requirement: 1 nibble per pixel..
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        if ((q - outbuf) + h->rects[object_id]->w*h->rects[object_id]->h/2
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            + 17*rects + 21 > outbuf_size) {
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            av_log(NULL, AV_LOG_ERROR, "dvd_subtitle too big\n");
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            return -1;
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        }
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        dvd_encode_rle(&q, h->rects[object_id]->pict.data[0],
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                       h->rects[object_id]->w*2,
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                       h->rects[object_id]->w, h->rects[object_id]->h >> 1,
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                       cmap);
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        offset2[object_id] = q - outbuf;
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        dvd_encode_rle(&q, h->rects[object_id]->pict.data[0] + h->rects[object_id]->w,
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                       h->rects[object_id]->w*2,
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                       h->rects[object_id]->w, h->rects[object_id]->h >> 1,
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                       cmap);
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    }
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    // set data packet size
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    qq = outbuf + 2;
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    bytestream_put_be16(&qq, q - outbuf);
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    // send start display command
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    bytestream_put_be16(&q, (h->start_display_time*90) >> 10);
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    bytestream_put_be16(&q, (q - outbuf) /*- 2 */ + 8 + 12*rects + 2);
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    *q++ = 0x03; // palette - 4 nibbles
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    *q++ = 0x03; *q++ = 0x7f;
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    *q++ = 0x04; // alpha - 4 nibbles
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    *q++ = 0xf0; *q++ = 0x00;
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    //*q++ = 0x0f; *q++ = 0xff;
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    // XXX not sure if more than one rect can really be encoded..
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    // 12 bytes per rect
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    for (object_id = 0; object_id < rects; object_id++) {
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        int x2 = h->rects[object_id]->x + h->rects[object_id]->w - 1;
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        int y2 = h->rects[object_id]->y + h->rects[object_id]->h - 1;
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        *q++ = 0x05;
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        // x1 x2 -> 6 nibbles
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        *q++ = h->rects[object_id]->x >> 4;
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        *q++ = (h->rects[object_id]->x << 4) | ((x2 >> 8) & 0xf);
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        *q++ = x2;
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        // y1 y2 -> 6 nibbles
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        *q++ = h->rects[object_id]->y >> 4;
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        *q++ = (h->rects[object_id]->y << 4) | ((y2 >> 8) & 0xf);
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        *q++ = y2;
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        *q++ = 0x06;
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        // offset1, offset2
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        bytestream_put_be16(&q, offset1[object_id]);
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        bytestream_put_be16(&q, offset2[object_id]);
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    }
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    *q++ = 0x01; // start command
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    *q++ = 0xff; // terminating command
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    // send stop display command last
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    bytestream_put_be16(&q, (h->end_display_time*90) >> 10);
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    bytestream_put_be16(&q, (q - outbuf) - 2 /*+ 4*/);
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    *q++ = 0x02; // set end
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    *q++ = 0xff; // terminating command
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    qq = outbuf;
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    bytestream_put_be16(&qq, q - outbuf);
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    av_log(NULL, AV_LOG_DEBUG, "subtitle_packet size=%td\n", q - outbuf);
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    return q - outbuf;
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}
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static int dvdsub_encode(AVCodecContext *avctx,
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                         unsigned char *buf, int buf_size, void *data)
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{
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    //DVDSubtitleContext *s = avctx->priv_data;
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    AVSubtitle *sub = data;
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    int ret;
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    ret = encode_dvd_subtitles(buf, buf_size, sub);
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    return ret;
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}
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AVCodec ff_dvdsub_encoder = {
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    "dvdsub",
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    AVMEDIA_TYPE_SUBTITLE,
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    CODEC_ID_DVD_SUBTITLE,
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    0,
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    NULL,
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    dvdsub_encode,
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    .long_name = NULL_IF_CONFIG_SMALL("DVD subtitles"),
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};