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ffmpeg/libavcodec/dvdsubenc.c

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/*
* DVD subtitle encoding for ffmpeg
* Copyright (c) 2005 Wolfram Gloger
*
* This file is part of Libav.
*
* Libav 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 2.1 of the License, or (at your option) any later version.
*
* Libav 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 Libav; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "avcodec.h"
#include "bytestream.h"
#undef NDEBUG
#include <assert.h>
// 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 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]->pict.data[0][i];
// only count non-transparent pixels
alpha = ((uint32_t*)h->rects[object_id]->pict.data[1])[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]->pict.data[0],
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]->pict.data[0] + 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;
bytestream_put_be16(&qq, q - outbuf);
// send start display command
bytestream_put_be16(&q, (h->start_display_time*90) >> 10);
bytestream_put_be16(&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
bytestream_put_be16(&q, offset1[object_id]);
bytestream_put_be16(&q, offset2[object_id]);
}
*q++ = 0x01; // start command
*q++ = 0xff; // terminating command
// send stop display command last
bytestream_put_be16(&q, (h->end_display_time*90) >> 10);
bytestream_put_be16(&q, (q - outbuf) - 2 /*+ 4*/);
*q++ = 0x02; // set end
*q++ = 0xff; // terminating command
qq = outbuf;
bytestream_put_be16(&qq, q - outbuf);
av_log(NULL, AV_LOG_DEBUG, "subtitle_packet size=%td\n", q - outbuf);
return q - outbuf;
}
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 ff_dvdsub_encoder = {
.name = "dvdsub",
.type = AVMEDIA_TYPE_SUBTITLE,
.id = CODEC_ID_DVD_SUBTITLE,
.encode = dvdsub_encode,
.long_name = NULL_IF_CONFIG_SMALL("DVD subtitles"),
};
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