ttmlenc.c
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/*
* TTML subtitle encoder
* Copyright (c) 2020 24i
*
* 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
*/
/**
* @file
* TTML subtitle encoder
* @see https://www.w3.org/TR/ttml1/
* @see https://www.w3.org/TR/ttml2/
* @see https://www.w3.org/TR/ttml-imsc/rec
*/
#include "avcodec.h"
#include "internal.h"
#include "libavutil/avstring.h"
#include "libavutil/bprint.h"
#include "libavutil/internal.h"
#include "ass_split.h"
#include "ass.h"
#include "ttmlenc.h"
typedef struct {
AVCodecContext *avctx;
ASSSplitContext *ass_ctx;
AVBPrint buffer;
} TTMLContext;
static void ttml_text_cb(void *priv, const char *text, int len)
{
TTMLContext *s = priv;
AVBPrint cur_line = { 0 };
AVBPrint *buffer = &s->buffer;
av_bprint_init(&cur_line, len, AV_BPRINT_SIZE_UNLIMITED);
av_bprint_append_data(&cur_line, text, len);
if (!av_bprint_is_complete(&cur_line)) {
av_log(s->avctx, AV_LOG_ERROR,
"Failed to move the current subtitle dialog to AVBPrint!\n");
av_bprint_finalize(&cur_line, NULL);
return;
}
av_bprint_escape(buffer, cur_line.str, NULL, AV_ESCAPE_MODE_XML,
0);
av_bprint_finalize(&cur_line, NULL);
}
static void ttml_new_line_cb(void *priv, int forced)
{
TTMLContext *s = priv;
av_bprintf(&s->buffer, "<br/>");
}
static const ASSCodesCallbacks ttml_callbacks = {
.text = ttml_text_cb,
.new_line = ttml_new_line_cb,
};
static int ttml_encode_frame(AVCodecContext *avctx, uint8_t *buf,
int bufsize, const AVSubtitle *sub)
{
TTMLContext *s = avctx->priv_data;
ASSDialog *dialog;
int i;
av_bprint_clear(&s->buffer);
for (i=0; i<sub->num_rects; i++) {
const char *ass = sub->rects[i]->ass;
if (sub->rects[i]->type != SUBTITLE_ASS) {
av_log(avctx, AV_LOG_ERROR, "Only SUBTITLE_ASS type supported.\n");
return AVERROR(EINVAL);
}
#if FF_API_ASS_TIMING
if (!strncmp(ass, "Dialogue: ", 10)) {
int num;
dialog = ff_ass_split_dialog(s->ass_ctx, ass, 0, &num);
for (; dialog && num--; dialog++) {
int ret = ff_ass_split_override_codes(&ttml_callbacks, s,
dialog->text);
int log_level = (ret != AVERROR_INVALIDDATA ||
avctx->err_recognition & AV_EF_EXPLODE) ?
AV_LOG_ERROR : AV_LOG_WARNING;
if (ret < 0) {
av_log(avctx, log_level,
"Splitting received ASS dialog failed: %s\n",
av_err2str(ret));
if (log_level == AV_LOG_ERROR)
return ret;
}
}
} else {
#endif
dialog = ff_ass_split_dialog2(s->ass_ctx, ass);
if (!dialog)
return AVERROR(ENOMEM);
{
int ret = ff_ass_split_override_codes(&ttml_callbacks, s,
dialog->text);
int log_level = (ret != AVERROR_INVALIDDATA ||
avctx->err_recognition & AV_EF_EXPLODE) ?
AV_LOG_ERROR : AV_LOG_WARNING;
if (ret < 0) {
av_log(avctx, log_level,
"Splitting received ASS dialog text %s failed: %s\n",
dialog->text,
av_err2str(ret));
if (log_level == AV_LOG_ERROR) {
ff_ass_free_dialog(&dialog);
return ret;
}
}
ff_ass_free_dialog(&dialog);
}
#if FF_API_ASS_TIMING
}
#endif
}
if (!av_bprint_is_complete(&s->buffer))
return AVERROR(ENOMEM);
if (!s->buffer.len)
return 0;
// force null-termination, so in case our destination buffer is
// too small, the return value is larger than bufsize minus null.
if (av_strlcpy(buf, s->buffer.str, bufsize) > bufsize - 1) {
av_log(avctx, AV_LOG_ERROR, "Buffer too small for TTML event.\n");
return AVERROR_BUFFER_TOO_SMALL;
}
return s->buffer.len;
}
static av_cold int ttml_encode_close(AVCodecContext *avctx)
{
TTMLContext *s = avctx->priv_data;
ff_ass_split_free(s->ass_ctx);
av_bprint_finalize(&s->buffer, NULL);
return 0;
}
static av_cold int ttml_encode_init(AVCodecContext *avctx)
{
TTMLContext *s = avctx->priv_data;
s->avctx = avctx;
if (!(s->ass_ctx = ff_ass_split(avctx->subtitle_header))) {
return AVERROR_INVALIDDATA;
}
if (!(avctx->extradata = av_mallocz(TTMLENC_EXTRADATA_SIGNATURE_SIZE +
1 + AV_INPUT_BUFFER_PADDING_SIZE))) {
return AVERROR(ENOMEM);
}
avctx->extradata_size = TTMLENC_EXTRADATA_SIGNATURE_SIZE;
memcpy(avctx->extradata, TTMLENC_EXTRADATA_SIGNATURE,
TTMLENC_EXTRADATA_SIGNATURE_SIZE);
av_bprint_init(&s->buffer, 0, AV_BPRINT_SIZE_UNLIMITED);
return 0;
}
AVCodec ff_ttml_encoder = {
.name = "ttml",
.long_name = NULL_IF_CONFIG_SMALL("TTML subtitle"),
.type = AVMEDIA_TYPE_SUBTITLE,
.id = AV_CODEC_ID_TTML,
.priv_data_size = sizeof(TTMLContext),
.init = ttml_encode_init,
.encode_sub = ttml_encode_frame,
.close = ttml_encode_close,
.caps_internal = FF_CODEC_CAP_INIT_CLEANUP,
};