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FFmpeg/libavcodec/movtextdec.c
wm4 b0644c3e1a movtextdec: fix handling of UTF-8 subtitles 
Subtitles which contained styled UTF-8 subtitles (i.e. not just 7 bit
ASCII characters) were not handled correctly. The spec mandates that
styling start/end ranges are in "characters". It's not quite clear what
a "character" is supposed to be, but maybe they mean unicode codepoints.

FFmpeg's decoder treated the style ranges as byte idexes, which could
lead to UTF-8 sequences being broken, and the common code dropping the
whole subtitle line.

Change this and count the codepoint instead. This also means that even
if this is somehow wrong, the decoder won't break UTF-8 sequences
anymore. The sample which led me to investigate this now appears to work
correctly.
2018-03-25 19:27:02 +02:00

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/*
* 3GPP TS 26.245 Timed Text decoder
* Copyright (c) 2012 Philip Langdale <philipl@overt.org>
*
* 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 "ass.h"
#include "libavutil/avstring.h"
#include "libavutil/common.h"
#include "libavutil/bprint.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/mem.h"
#define STYLE_FLAG_BOLD (1<<0)
#define STYLE_FLAG_ITALIC (1<<1)
#define STYLE_FLAG_UNDERLINE (1<<2)
#define BOX_SIZE_INITIAL 40
#define STYL_BOX (1<<0)
#define HLIT_BOX (1<<1)
#define HCLR_BOX (1<<2)
#define TWRP_BOX (1<<3)
#define BOTTOM_LEFT 1
#define BOTTOM_CENTER 2
#define BOTTOM_RIGHT 3
#define MIDDLE_LEFT 4
#define MIDDLE_CENTER 5
#define MIDDLE_RIGHT 6
#define TOP_LEFT 7
#define TOP_CENTER 8
#define TOP_RIGHT 9
typedef struct {
char *font;
int fontsize;
int color;
int back_color;
int bold;
int italic;
int underline;
int alignment;
} MovTextDefault;
typedef struct {
uint16_t fontID;
char *font;
} FontRecord;
typedef struct {
uint16_t style_start;
uint16_t style_end;
uint8_t style_flag;
uint8_t fontsize;
uint16_t style_fontID;
} StyleBox;
typedef struct {
uint16_t hlit_start;
uint16_t hlit_end;
} HighlightBox;
typedef struct {
uint8_t hlit_color[4];
} HilightcolorBox;
typedef struct {
uint8_t wrap_flag;
} TextWrapBox;
typedef struct {
StyleBox **s;
StyleBox *s_temp;
HighlightBox h;
HilightcolorBox c;
FontRecord **ftab;
FontRecord *ftab_temp;
TextWrapBox w;
MovTextDefault d;
uint8_t box_flags;
uint16_t style_entries, ftab_entries;
uint64_t tracksize;
int size_var;
int count_s, count_f;
int readorder;
} MovTextContext;
typedef struct {
uint32_t type;
size_t base_size;
int (*decode)(const uint8_t *tsmb, MovTextContext *m, AVPacket *avpkt);
} Box;
static void mov_text_cleanup(MovTextContext *m)
{
int i;
if (m->box_flags & STYL_BOX) {
for(i = 0; i < m->count_s; i++) {
av_freep(&m->s[i]);
}
av_freep(&m->s);
m->count_s = 0;
m->style_entries = 0;
}
}
static void mov_text_cleanup_ftab(MovTextContext *m)
{
int i;
if (m->ftab_temp)
av_freep(&m->ftab_temp->font);
av_freep(&m->ftab_temp);
if (m->ftab) {
for(i = 0; i < m->count_f; i++) {
av_freep(&m->ftab[i]->font);
av_freep(&m->ftab[i]);
}
}
av_freep(&m->ftab);
}
static int mov_text_tx3g(AVCodecContext *avctx, MovTextContext *m)
{
uint8_t *tx3g_ptr = avctx->extradata;
int i, box_size, font_length;
int8_t v_align, h_align;
int style_fontID;
StyleBox s_default;
m->count_f = 0;
m->ftab_entries = 0;
box_size = BOX_SIZE_INITIAL; /* Size till ftab_entries */
if (avctx->extradata_size < box_size)
return -1;
// Display Flags
tx3g_ptr += 4;
// Alignment
h_align = *tx3g_ptr++;
v_align = *tx3g_ptr++;
if (h_align == 0) {
if (v_align == 0)
m->d.alignment = TOP_LEFT;
if (v_align == 1)
m->d.alignment = MIDDLE_LEFT;
if (v_align == -1)
m->d.alignment = BOTTOM_LEFT;
}
if (h_align == 1) {
if (v_align == 0)
m->d.alignment = TOP_CENTER;
if (v_align == 1)
m->d.alignment = MIDDLE_CENTER;
if (v_align == -1)
m->d.alignment = BOTTOM_CENTER;
}
if (h_align == -1) {
if (v_align == 0)
m->d.alignment = TOP_RIGHT;
if (v_align == 1)
m->d.alignment = MIDDLE_RIGHT;
if (v_align == -1)
m->d.alignment = BOTTOM_RIGHT;
}
// Background Color
m->d.back_color = AV_RB24(tx3g_ptr);
tx3g_ptr += 4;
// BoxRecord
tx3g_ptr += 8;
// StyleRecord
tx3g_ptr += 4;
// fontID
style_fontID = AV_RB16(tx3g_ptr);
tx3g_ptr += 2;
// face-style-flags
s_default.style_flag = *tx3g_ptr++;
m->d.bold = s_default.style_flag & STYLE_FLAG_BOLD;
m->d.italic = s_default.style_flag & STYLE_FLAG_ITALIC;
m->d.underline = s_default.style_flag & STYLE_FLAG_UNDERLINE;
// fontsize
m->d.fontsize = *tx3g_ptr++;
// Primary color
m->d.color = AV_RB24(tx3g_ptr);
tx3g_ptr += 4;
// FontRecord
// FontRecord Size
tx3g_ptr += 4;
// ftab
tx3g_ptr += 4;
m->ftab_entries = AV_RB16(tx3g_ptr);
tx3g_ptr += 2;
for (i = 0; i < m->ftab_entries; i++) {
box_size += 3;
if (avctx->extradata_size < box_size) {
mov_text_cleanup_ftab(m);
m->ftab_entries = 0;
return -1;
}
m->ftab_temp = av_mallocz(sizeof(*m->ftab_temp));
if (!m->ftab_temp) {
mov_text_cleanup_ftab(m);
return AVERROR(ENOMEM);
}
m->ftab_temp->fontID = AV_RB16(tx3g_ptr);
tx3g_ptr += 2;
font_length = *tx3g_ptr++;
box_size = box_size + font_length;
if (avctx->extradata_size < box_size) {
mov_text_cleanup_ftab(m);
m->ftab_entries = 0;
return -1;
}
m->ftab_temp->font = av_malloc(font_length + 1);
if (!m->ftab_temp->font) {
mov_text_cleanup_ftab(m);
return AVERROR(ENOMEM);
}
memcpy(m->ftab_temp->font, tx3g_ptr, font_length);
m->ftab_temp->font[font_length] = '\0';
av_dynarray_add(&m->ftab, &m->count_f, m->ftab_temp);
if (!m->ftab) {
mov_text_cleanup_ftab(m);
return AVERROR(ENOMEM);
}
m->ftab_temp = NULL;
tx3g_ptr = tx3g_ptr + font_length;
}
for (i = 0; i < m->ftab_entries; i++) {
if (style_fontID == m->ftab[i]->fontID)
m->d.font = m->ftab[i]->font;
}
return 0;
}
static int decode_twrp(const uint8_t *tsmb, MovTextContext *m, AVPacket *avpkt)
{
m->box_flags |= TWRP_BOX;
m->w.wrap_flag = *tsmb++;
return 0;
}
static int decode_hlit(const uint8_t *tsmb, MovTextContext *m, AVPacket *avpkt)
{
m->box_flags |= HLIT_BOX;
m->h.hlit_start = AV_RB16(tsmb);
tsmb += 2;
m->h.hlit_end = AV_RB16(tsmb);
tsmb += 2;
return 0;
}
static int decode_hclr(const uint8_t *tsmb, MovTextContext *m, AVPacket *avpkt)
{
m->box_flags |= HCLR_BOX;
memcpy(m->c.hlit_color, tsmb, 4);
tsmb += 4;
return 0;
}
static int decode_styl(const uint8_t *tsmb, MovTextContext *m, AVPacket *avpkt)
{
int i;
int style_entries = AV_RB16(tsmb);
tsmb += 2;
// A single style record is of length 12 bytes.
if (m->tracksize + m->size_var + 2 + style_entries * 12 > avpkt->size)
return -1;
m->style_entries = style_entries;
m->box_flags |= STYL_BOX;
for(i = 0; i < m->style_entries; i++) {
m->s_temp = av_malloc(sizeof(*m->s_temp));
if (!m->s_temp) {
mov_text_cleanup(m);
return AVERROR(ENOMEM);
}
m->s_temp->style_start = AV_RB16(tsmb);
tsmb += 2;
m->s_temp->style_end = AV_RB16(tsmb);
tsmb += 2;
m->s_temp->style_fontID = AV_RB16(tsmb);
tsmb += 2;
m->s_temp->style_flag = AV_RB8(tsmb);
tsmb++;
m->s_temp->fontsize = AV_RB8(tsmb);
av_dynarray_add(&m->s, &m->count_s, m->s_temp);
if(!m->s) {
mov_text_cleanup(m);
return AVERROR(ENOMEM);
}
tsmb++;
// text-color-rgba
tsmb += 4;
}
return 0;
}
static const Box box_types[] = {
{ MKBETAG('s','t','y','l'), 2, decode_styl },
{ MKBETAG('h','l','i','t'), 4, decode_hlit },
{ MKBETAG('h','c','l','r'), 4, decode_hclr },
{ MKBETAG('t','w','r','p'), 1, decode_twrp }
};
const static size_t box_count = FF_ARRAY_ELEMS(box_types);
// Return byte length of the UTF-8 sequence starting at text[0]. 0 on error.
static int get_utf8_length_at(const char *text, const char *text_end)
{
const char *start = text;
int err = 0;
uint32_t c;
GET_UTF8(c, text < text_end ? (uint8_t)*text++ : (err = 1, 0), goto error;);
if (err)
goto error;
return text - start;
error:
return 0;
}
static int text_to_ass(AVBPrint *buf, const char *text, const char *text_end,
AVCodecContext *avctx)
{
MovTextContext *m = avctx->priv_data;
int i = 0;
int j = 0;
int text_pos = 0;
if (text < text_end && m->box_flags & TWRP_BOX) {
if (m->w.wrap_flag == 1) {
av_bprintf(buf, "{\\q1}"); /* End of line wrap */
} else {
av_bprintf(buf, "{\\q2}"); /* No wrap */
}
}
while (text < text_end) {
int len;
if (m->box_flags & STYL_BOX) {
for (i = 0; i < m->style_entries; i++) {
if (m->s[i]->style_flag && text_pos == m->s[i]->style_end) {
av_bprintf(buf, "{\\r}");
}
}
for (i = 0; i < m->style_entries; i++) {
if (m->s[i]->style_flag && text_pos == m->s[i]->style_start) {
if (m->s[i]->style_flag & STYLE_FLAG_BOLD)
av_bprintf(buf, "{\\b1}");
if (m->s[i]->style_flag & STYLE_FLAG_ITALIC)
av_bprintf(buf, "{\\i1}");
if (m->s[i]->style_flag & STYLE_FLAG_UNDERLINE)
av_bprintf(buf, "{\\u1}");
av_bprintf(buf, "{\\fs%d}", m->s[i]->fontsize);
for (j = 0; j < m->ftab_entries; j++) {
if (m->s[i]->style_fontID == m->ftab[j]->fontID)
av_bprintf(buf, "{\\fn%s}", m->ftab[j]->font);
}
}
}
}
if (m->box_flags & HLIT_BOX) {
if (text_pos == m->h.hlit_start) {
/* If hclr box is present, set the secondary color to the color
* specified. Otherwise, set primary color to white and secondary
* color to black. These colors will come from TextSampleModifier
* boxes in future and inverse video technique for highlight will
* be implemented.
*/
if (m->box_flags & HCLR_BOX) {
av_bprintf(buf, "{\\2c&H%02x%02x%02x&}", m->c.hlit_color[2],
m->c.hlit_color[1], m->c.hlit_color[0]);
} else {
av_bprintf(buf, "{\\1c&H000000&}{\\2c&HFFFFFF&}");
}
}
if (text_pos == m->h.hlit_end) {
if (m->box_flags & HCLR_BOX) {
av_bprintf(buf, "{\\2c&H000000&}");
} else {
av_bprintf(buf, "{\\1c&HFFFFFF&}{\\2c&H000000&}");
}
}
}
len = get_utf8_length_at(text, text_end);
if (len < 1) {
av_log(avctx, AV_LOG_ERROR, "invalid UTF-8 byte in subtitle\n");
len = 1;
}
for (i = 0; i < len; i++) {
switch (*text) {
case '\r':
break;
case '\n':
av_bprintf(buf, "\\N");
break;
default:
av_bprint_chars(buf, *text, 1);
break;
}
text++;
}
text_pos++;
}
return 0;
}
static int mov_text_init(AVCodecContext *avctx) {
/*
* TODO: Handle the default text style.
* NB: Most players ignore styles completely, with the result that
* it's very common to find files where the default style is broken
* and respecting it results in a worse experience than ignoring it.
*/
int ret;
MovTextContext *m = avctx->priv_data;
ret = mov_text_tx3g(avctx, m);
if (ret == 0) {
return ff_ass_subtitle_header(avctx, m->d.font, m->d.fontsize, m->d.color,
m->d.back_color, m->d.bold, m->d.italic,
m->d.underline, ASS_DEFAULT_BORDERSTYLE,
m->d.alignment);
} else
return ff_ass_subtitle_header_default(avctx);
}
static int mov_text_decode_frame(AVCodecContext *avctx,
void *data, int *got_sub_ptr, AVPacket *avpkt)
{
AVSubtitle *sub = data;
MovTextContext *m = avctx->priv_data;
int ret;
AVBPrint buf;
char *ptr = avpkt->data;
char *end;
int text_length, tsmb_type, ret_tsmb;
uint64_t tsmb_size;
const uint8_t *tsmb;
size_t i;
if (!ptr || avpkt->size < 2)
return AVERROR_INVALIDDATA;
/*
* A packet of size two with value zero is an empty subtitle
* used to mark the end of the previous non-empty subtitle.
* We can just drop them here as we have duration information
* already. If the value is non-zero, then it's technically a
* bad packet.
*/
if (avpkt->size == 2)
return AV_RB16(ptr) == 0 ? 0 : AVERROR_INVALIDDATA;
/*
* The first two bytes of the packet are the length of the text string
* In complex cases, there are style descriptors appended to the string
* so we can't just assume the packet size is the string size.
*/
text_length = AV_RB16(ptr);
end = ptr + FFMIN(2 + text_length, avpkt->size);
ptr += 2;
mov_text_cleanup(m);
tsmb_size = 0;
m->tracksize = 2 + text_length;
m->style_entries = 0;
m->box_flags = 0;
m->count_s = 0;
// Note that the spec recommends lines be no longer than 2048 characters.
av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);
if (text_length + 2 != avpkt->size) {
while (m->tracksize + 8 <= avpkt->size) {
// A box is a minimum of 8 bytes.
tsmb = ptr + m->tracksize - 2;
tsmb_size = AV_RB32(tsmb);
tsmb += 4;
tsmb_type = AV_RB32(tsmb);
tsmb += 4;
if (tsmb_size == 1) {
if (m->tracksize + 16 > avpkt->size)
break;
tsmb_size = AV_RB64(tsmb);
tsmb += 8;
m->size_var = 16;
} else
m->size_var = 8;
//size_var is equal to 8 or 16 depending on the size of box
if (tsmb_size == 0) {
av_log(avctx, AV_LOG_ERROR, "tsmb_size is 0\n");
return AVERROR_INVALIDDATA;
}
if (tsmb_size > avpkt->size - m->tracksize)
break;
for (i = 0; i < box_count; i++) {
if (tsmb_type == box_types[i].type) {
if (m->tracksize + m->size_var + box_types[i].base_size > avpkt->size)
break;
ret_tsmb = box_types[i].decode(tsmb, m, avpkt);
if (ret_tsmb == -1)
break;
}
}
m->tracksize = m->tracksize + tsmb_size;
}
text_to_ass(&buf, ptr, end, avctx);
mov_text_cleanup(m);
} else
text_to_ass(&buf, ptr, end, avctx);
ret = ff_ass_add_rect(sub, buf.str, m->readorder++, 0, NULL, NULL);
av_bprint_finalize(&buf, NULL);
if (ret < 0)
return ret;
*got_sub_ptr = sub->num_rects > 0;
return avpkt->size;
}
static int mov_text_decode_close(AVCodecContext *avctx)
{
MovTextContext *m = avctx->priv_data;
mov_text_cleanup_ftab(m);
mov_text_cleanup(m);
return 0;
}
static void mov_text_flush(AVCodecContext *avctx)
{
MovTextContext *m = avctx->priv_data;
if (!(avctx->flags2 & AV_CODEC_FLAG2_RO_FLUSH_NOOP))
m->readorder = 0;
}
AVCodec ff_movtext_decoder = {
.name = "mov_text",
.long_name = NULL_IF_CONFIG_SMALL("3GPP Timed Text subtitle"),
.type = AVMEDIA_TYPE_SUBTITLE,
.id = AV_CODEC_ID_MOV_TEXT,
.priv_data_size = sizeof(MovTextContext),
.init = mov_text_init,
.decode = mov_text_decode_frame,
.close = mov_text_decode_close,
.flush = mov_text_flush,
};
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