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FFmpeg/libavcodec/dvdsubenc.c
Oliver Fromme a32dcaaaf8 avcodec/dvdsubenc: Add dvdsub workaround for some players 
The issue affects dvdsub subtitles (a.k.a. VOBSUB).

Some players -- in particular hardware players -- cut off
the lowest row of pixels if the number of rows in the subtitle
is odd.

The patch below implements a work-around for that.  If the
number of rows is odd, it is simply rounded up to an even
number, adding an invisible (i.e. fully transparent) row.
The work-around can be enabled or disabled with a new
option -even_rows_fix.  The default is disabled, so there
is no change of behaviour for users who don't care about it.

The overhead for the fix is low, and in many cases even zero:
For subtitles with an odd number of rows (i.e. in 50% of
cases on average), the size increases by two bytes because
a fully transparent row is encoded as 0x00 0x00.  However,
in the VOBSUB standard, all data packets are padded to 2KB
anyway, so in most cases the additional bytes just use some
part of the padding, so there is no overhead.  Only in the
rare case that the 2KB boundary is hit (0.1% chance), a full
2KB block is added.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
2014-07-09 20:11:36 +02:00

476 lines
15 KiB
C
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/*
* DVD subtitle encoding
* Copyright (c) 2005 Wolfram Gloger
*
* This file is part of FFmpeg.
*
* FFmpeg 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.
*
* FFmpeg 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 FFmpeg; 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"
#include "internal.h"
#include "libavutil/avassert.h"
#include "libavutil/bprint.h"
#include "libavutil/imgutils.h"
#include "libavutil/opt.h"
typedef struct {
AVClass *class;
uint32_t global_palette[16];
int even_rows_fix;
} 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];
av_assert0(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 color_distance(uint32_t a, uint32_t b)
{
int r = 0, d, i;
int alpha_a = 8, alpha_b = 8;
for (i = 24; i >= 0; i -= 8) {
d = alpha_a * (int)((a >> i) & 0xFF) -
alpha_b * (int)((b >> i) & 0xFF);
r += d * d;
alpha_a = a >> 28;
alpha_b = b >> 28;
}
return r;
}
/**
* Count colors used in a rectangle, quantizing alpha and grouping by
* nearest global palette entry.
*/
static void count_colors(AVCodecContext *avctx, unsigned hits[33],
const AVSubtitleRect *r)
{
DVDSubtitleContext *dvdc = avctx->priv_data;
unsigned count[256] = { 0 };
uint32_t *palette = (uint32_t *)r->pict.data[1];
uint32_t color;
int x, y, i, j, match, d, best_d, av_uninit(best_j);
uint8_t *p = r->pict.data[0];
for (y = 0; y < r->h; y++) {
for (x = 0; x < r->w; x++)
count[*(p++)]++;
p += r->pict.linesize[0] - r->w;
}
for (i = 0; i < 256; i++) {
if (!count[i]) /* avoid useless search */
continue;
color = palette[i];
/* 0: transparent, 1-16: semi-transparent, 17-33 opaque */
match = color < 0x33000000 ? 0 : color < 0xCC000000 ? 1 : 17;
if (match) {
best_d = INT_MAX;
for (j = 0; j < 16; j++) {
d = color_distance(0xFF000000 | color,
0xFF000000 | dvdc->global_palette[j]);
if (d < best_d) {
best_d = d;
best_j = j;
}
}
match += best_j;
}
hits[match] += count[i];
}
}
static void select_palette(AVCodecContext *avctx, int out_palette[4],
int out_alpha[4], unsigned hits[33])
{
DVDSubtitleContext *dvdc = avctx->priv_data;
int i, j, bright, mult;
uint32_t color;
int selected[4] = { 0 };
uint32_t pseudopal[33] = { 0 };
uint32_t refcolor[3] = { 0x00000000, 0xFFFFFFFF, 0xFF000000 };
/* Bonus for transparent: if the rectangle fits tightly the text, the
background color can be quite rare, but it would be ugly without it */
hits[0] *= 16;
/* Bonus for bright colors */
for (i = 0; i < 16; i++) {
if (!(hits[1 + i] + hits[17 + i]))
continue; /* skip unused colors to gain time */
color = dvdc->global_palette[i];
bright = 0;
for (j = 0; j < 3; j++, color >>= 8)
bright += (color & 0xFF) < 0x40 || (color & 0xFF) >= 0xC0;
mult = 2 + FFMIN(bright, 2);
hits[ 1 + i] *= mult;
hits[17 + i] *= mult;
}
/* Select four most frequent colors */
for (i = 0; i < 4; i++) {
for (j = 0; j < 33; j++)
if (hits[j] > hits[selected[i]])
selected[i] = j;
hits[selected[i]] = 0;
}
/* Order the colors like in most DVDs:
0: background, 1: foreground, 2: outline */
for (i = 0; i < 16; i++) {
pseudopal[ 1 + i] = 0x80000000 | dvdc->global_palette[i];
pseudopal[17 + i] = 0xFF000000 | dvdc->global_palette[i];
}
for (i = 0; i < 3; i++) {
int best_d = color_distance(refcolor[i], pseudopal[selected[i]]);
for (j = i + 1; j < 4; j++) {
int d = color_distance(refcolor[i], pseudopal[selected[j]]);
if (d < best_d) {
FFSWAP(int, selected[i], selected[j]);
best_d = d;
}
}
}
/* Output */
for (i = 0; i < 4; i++) {
out_palette[i] = selected[i] ? (selected[i] - 1) & 0xF : 0;
out_alpha [i] = !selected[i] ? 0 : selected[i] < 17 ? 0x80 : 0xFF;
}
}
static void build_color_map(AVCodecContext *avctx, int cmap[],
const uint32_t palette[],
const int out_palette[], unsigned int const out_alpha[])
{
DVDSubtitleContext *dvdc = avctx->priv_data;
int i, j, d, best_d;
uint32_t pseudopal[4];
for (i = 0; i < 4; i++)
pseudopal[i] = (out_alpha[i] << 24) |
dvdc->global_palette[out_palette[i]];
for (i = 0; i < 256; i++) {
best_d = INT_MAX;
for (j = 0; j < 4; j++) {
d = color_distance(pseudopal[j], palette[i]);
if (d < best_d) {
cmap[i] = j;
best_d = d;
}
}
}
}
static void copy_rectangle(AVSubtitleRect *dst, AVSubtitleRect *src, int cmap[])
{
int x, y;
uint8_t *p, *q;
p = src->pict.data[0];
q = dst->pict.data[0] + (src->x - dst->x) +
(src->y - dst->y) * dst->pict.linesize[0];
for (y = 0; y < src->h; y++) {
for (x = 0; x < src->w; x++)
*(q++) = cmap[*(p++)];
p += src->pict.linesize[0] - src->w;
q += dst->pict.linesize[0] - src->w;
}
}
static int encode_dvd_subtitles(AVCodecContext *avctx,
uint8_t *outbuf, int outbuf_size,
const AVSubtitle *h)
{
DVDSubtitleContext *dvdc = avctx->priv_data;
uint8_t *q, *qq;
int offset1, offset2;
int i, rects = h->num_rects, ret;
unsigned global_palette_hits[33] = { 0 };
int cmap[256];
int out_palette[4];
int out_alpha[4];
AVSubtitleRect vrect;
uint8_t *vrect_data = NULL;
int x2, y2;
int forced = 0;
if (rects == 0 || h->rects == NULL)
return AVERROR(EINVAL);
for (i = 0; i < rects; i++)
if (h->rects[i]->type != SUBTITLE_BITMAP) {
av_log(avctx, AV_LOG_ERROR, "Bitmap subtitle required\n");
return AVERROR(EINVAL);
}
/* Mark this subtitle forced if any of the rectangles is forced. */
for (i = 0; i < rects; i++)
if ((h->rects[i]->flags & AV_SUBTITLE_FLAG_FORCED) != 0) {
forced = 1;
break;
}
vrect = *h->rects[0];
if (rects > 1) {
/* DVD subtitles can have only one rectangle: build a virtual
rectangle containing all actual rectangles.
The data of the rectangles will be copied later, when the palette
is decided, because the rectangles may have different palettes. */
int xmin = h->rects[0]->x, xmax = xmin + h->rects[0]->w;
int ymin = h->rects[0]->y, ymax = ymin + h->rects[0]->h;
for (i = 1; i < rects; i++) {
xmin = FFMIN(xmin, h->rects[i]->x);
ymin = FFMIN(ymin, h->rects[i]->y);
xmax = FFMAX(xmax, h->rects[i]->x + h->rects[i]->w);
ymax = FFMAX(ymax, h->rects[i]->y + h->rects[i]->h);
}
vrect.x = xmin;
vrect.y = ymin;
vrect.w = xmax - xmin;
vrect.h = ymax - ymin;
if ((ret = av_image_check_size(vrect.w, vrect.h, 0, avctx)) < 0)
return ret;
/* Count pixels outside the virtual rectangle as transparent */
global_palette_hits[0] = vrect.w * vrect.h;
for (i = 0; i < rects; i++)
global_palette_hits[0] -= h->rects[i]->w * h->rects[i]->h;
}
for (i = 0; i < rects; i++)
count_colors(avctx, global_palette_hits, h->rects[i]);
select_palette(avctx, out_palette, out_alpha, global_palette_hits);
if (rects > 1) {
if (!(vrect_data = av_calloc(vrect.w, vrect.h)))
return AVERROR(ENOMEM);
vrect.pict.data [0] = vrect_data;
vrect.pict.linesize[0] = vrect.w;
for (i = 0; i < rects; i++) {
build_color_map(avctx, cmap, (uint32_t *)h->rects[i]->pict.data[1],
out_palette, out_alpha);
copy_rectangle(&vrect, h->rects[i], cmap);
}
for (i = 0; i < 4; i++)
cmap[i] = i;
} else {
build_color_map(avctx, cmap, (uint32_t *)h->rects[0]->pict.data[1],
out_palette, out_alpha);
}
av_log(avctx, AV_LOG_DEBUG, "Selected palette:");
for (i = 0; i < 4; i++)
av_log(avctx, AV_LOG_DEBUG, " 0x%06x@@%02x (0x%x,0x%x)",
dvdc->global_palette[out_palette[i]], out_alpha[i],
out_palette[i], out_alpha[i] >> 4);
av_log(avctx, AV_LOG_DEBUG, "\n");
// encode data block
q = outbuf + 4;
offset1 = q - outbuf;
// worst case memory requirement: 1 nibble per pixel..
if ((q - outbuf) + vrect.w * vrect.h / 2 + 17 + 21 > outbuf_size) {
av_log(NULL, AV_LOG_ERROR, "dvd_subtitle too big\n");
ret = AVERROR_BUFFER_TOO_SMALL;
goto fail;
}
dvd_encode_rle(&q, vrect.pict.data[0], vrect.w * 2,
vrect.w, (vrect.h + 1) >> 1, cmap);
offset2 = q - outbuf;
dvd_encode_rle(&q, vrect.pict.data[0] + vrect.w, vrect.w * 2,
vrect.w, vrect.h >> 1, cmap);
if (dvdc->even_rows_fix && (vrect.h & 1)) {
// Work-around for some players that want the height to be even.
vrect.h++;
*q++ = 0x00; // 0x00 0x00 == empty row, i.e. fully transparent
*q++ = 0x00;
}
// 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 + 2);
*q++ = 0x03; // palette - 4 nibbles
*q++ = (out_palette[3] << 4) | out_palette[2];
*q++ = (out_palette[1] << 4) | out_palette[0];
*q++ = 0x04; // alpha - 4 nibbles
*q++ = (out_alpha[3] & 0xF0) | (out_alpha[2] >> 4);
*q++ = (out_alpha[1] & 0xF0) | (out_alpha[0] >> 4);
// 12 bytes per rect
x2 = vrect.x + vrect.w - 1;
y2 = vrect.y + vrect.h - 1;
*q++ = 0x05;
// x1 x2 -> 6 nibbles
*q++ = vrect.x >> 4;
*q++ = (vrect.x << 4) | ((x2 >> 8) & 0xf);
*q++ = x2;
// y1 y2 -> 6 nibbles
*q++ = vrect.y >> 4;
*q++ = (vrect.y << 4) | ((y2 >> 8) & 0xf);
*q++ = y2;
*q++ = 0x06;
// offset1, offset2
bytestream_put_be16(&q, offset1);
bytestream_put_be16(&q, offset2);
*q++ = forced ? 0x00 : 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=%"PTRDIFF_SPECIFIER"\n", q - outbuf);
ret = q - outbuf;
fail:
av_free(vrect_data);
return ret;
}
static int dvdsub_init(AVCodecContext *avctx)
{
DVDSubtitleContext *dvdc = avctx->priv_data;
static const uint32_t default_palette[16] = {
0x000000, 0x0000FF, 0x00FF00, 0xFF0000,
0xFFFF00, 0xFF00FF, 0x00FFFF, 0xFFFFFF,
0x808000, 0x8080FF, 0x800080, 0x80FF80,
0x008080, 0xFF8080, 0x555555, 0xAAAAAA,
};
AVBPrint extradata;
int i, ret;
av_assert0(sizeof(dvdc->global_palette) == sizeof(default_palette));
memcpy(dvdc->global_palette, default_palette, sizeof(dvdc->global_palette));
av_bprint_init(&extradata, 0, 1);
if (avctx->width && avctx->height)
av_bprintf(&extradata, "size: %dx%d\n", avctx->width, avctx->height);
av_bprintf(&extradata, "palette:");
for (i = 0; i < 16; i++)
av_bprintf(&extradata, " %06"PRIx32"%c",
dvdc->global_palette[i] & 0xFFFFFF, i < 15 ? ',' : '\n');
ret = avpriv_bprint_to_extradata(avctx, &extradata);
if (ret < 0)
return ret;
return 0;
}
static int dvdsub_encode(AVCodecContext *avctx,
unsigned char *buf, int buf_size,
const AVSubtitle *sub)
{
//DVDSubtitleContext *s = avctx->priv_data;
int ret;
ret = encode_dvd_subtitles(avctx, buf, buf_size, sub);
return ret;
}
#define OFFSET(x) offsetof(DVDSubtitleContext, x)
#define SE AV_OPT_FLAG_SUBTITLE_PARAM | AV_OPT_FLAG_ENCODING_PARAM
static const AVOption options[] = {
{"even_rows_fix", "Make number of rows even (workaround for some players)", OFFSET(even_rows_fix), AV_OPT_TYPE_INT, {.i64 = 0}, 0, 1, SE},
{ NULL },
};
static const AVClass dvdsubenc_class = {
.class_name = "VOBSUB subtitle encoder",
.item_name = av_default_item_name,
.option = options,
.version = LIBAVUTIL_VERSION_INT,
};
AVCodec ff_dvdsub_encoder = {
.name = "dvdsub",
.long_name = NULL_IF_CONFIG_SMALL("DVD subtitles"),
.type = AVMEDIA_TYPE_SUBTITLE,
.id = AV_CODEC_ID_DVD_SUBTITLE,
.init = dvdsub_init,
.encode_sub = dvdsub_encode,
.priv_class = &dvdsubenc_class,
.priv_data_size = sizeof(DVDSubtitleContext),
};
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