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ffmpeg/libavformat/tedcaptionsdec.c

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/*
* TED Talks captions format decoder
* Copyright (c) 2012 Nicolas George
*
* 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 "libavutil/bprint.h"
#include "libavutil/log.h"
#include "libavutil/opt.h"
#include "avformat.h"
#include "internal.h"
#include "subtitles.h"
typedef struct {
AVClass *class;
int64_t start_time;
FFDemuxSubtitlesQueue subs;
} TEDCaptionsDemuxer;
static const AVOption tedcaptions_options[] = {
{ "start_time", "set the start time (offset) of the subtitles, in ms",
offsetof(TEDCaptionsDemuxer, start_time), AV_OPT_TYPE_INT64,
{ .i64 = 15000 }, INT64_MIN, INT64_MAX,
AV_OPT_FLAG_SUBTITLE_PARAM | AV_OPT_FLAG_DECODING_PARAM },
{ NULL },
};
static const AVClass tedcaptions_demuxer_class = {
.class_name = "tedcaptions_demuxer",
.item_name = av_default_item_name,
.option = tedcaptions_options,
.version = LIBAVUTIL_VERSION_INT,
};
#define BETWEEN(a, amin, amax) ((unsigned)((a) - (amin)) <= (amax) - (amin))
#define HEX_DIGIT_TEST(c) (BETWEEN(c, '0', '9') || BETWEEN((c) | 32, 'a', 'z'))
#define HEX_DIGIT_VAL(c) ((c) <= '9' ? (c) - '0' : ((c) | 32) - 'a' + 10)
#define ERR_CODE(c) ((c) < 0 ? (c) : AVERROR_INVALIDDATA)
static void av_bprint_utf8(AVBPrint *bp, unsigned c)
{
int bytes, i;
if (c <= 0x7F) {
av_bprint_chars(bp, c, 1);
return;
}
bytes = (av_log2(c) - 2) / 5;
av_bprint_chars(bp, (c >> (bytes * 6)) | ((0xFF80 >> bytes) & 0xFF), 1);
for (i = bytes - 1; i >= 0; i--)
av_bprint_chars(bp, ((c >> (i * 6)) & 0x3F) | 0x80, 1);
}
static void next_byte(AVIOContext *pb, int *cur_byte)
{
uint8_t b;
int ret = avio_read(pb, &b, 1);
*cur_byte = ret > 0 ? b : ret == 0 ? AVERROR_EOF : ret;
}
static void skip_spaces(AVIOContext *pb, int *cur_byte)
{
while (*cur_byte == ' ' || *cur_byte == '\t' ||
*cur_byte == '\n' || *cur_byte == '\r')
next_byte(pb, cur_byte);
}
static int expect_byte(AVIOContext *pb, int *cur_byte, uint8_t c)
{
skip_spaces(pb, cur_byte);
if (*cur_byte != c)
return ERR_CODE(*cur_byte);
next_byte(pb, cur_byte);
return 0;
}
static int parse_string(AVIOContext *pb, int *cur_byte, AVBPrint *bp, int full)
{
int ret;
av_bprint_init(bp, 0, full ? AV_BPRINT_SIZE_UNLIMITED : AV_BPRINT_SIZE_AUTOMATIC);
ret = expect_byte(pb, cur_byte, '"');
if (ret < 0)
goto fail;
while (*cur_byte > 0 && *cur_byte != '"') {
if (*cur_byte == '\\') {
next_byte(pb, cur_byte);
if (*cur_byte < 0) {
ret = AVERROR_INVALIDDATA;
goto fail;
}
if ((*cur_byte | 32) == 'u') {
unsigned chr = 0, i;
for (i = 0; i < 4; i++) {
next_byte(pb, cur_byte);
if (!HEX_DIGIT_TEST(*cur_byte)) {
ret = ERR_CODE(*cur_byte);
goto fail;
}
chr = chr * 16 + HEX_DIGIT_VAL(*cur_byte);
}
av_bprint_utf8(bp, chr);
} else {
av_bprint_chars(bp, *cur_byte, 1);
}
} else {
av_bprint_chars(bp, *cur_byte, 1);
}
next_byte(pb, cur_byte);
}
ret = expect_byte(pb, cur_byte, '"');
if (ret < 0)
goto fail;
if (full && !av_bprint_is_complete(bp)) {
ret = AVERROR(ENOMEM);
goto fail;
}
return 0;
fail:
av_bprint_finalize(bp, NULL);
return ret;
}
static int parse_label(AVIOContext *pb, int *cur_byte, AVBPrint *bp)
{
int ret;
ret = parse_string(pb, cur_byte, bp, 0);
if (ret < 0)
return ret;
ret = expect_byte(pb, cur_byte, ':');
if (ret < 0)
return ret;
return 0;
}
static int parse_boolean(AVIOContext *pb, int *cur_byte, int *result)
{
static const char * const text[] = { "false", "true" };
const char *p;
int i;
skip_spaces(pb, cur_byte);
for (i = 0; i < 2; i++) {
p = text[i];
if (*cur_byte != *p)
continue;
for (; *p; p++, next_byte(pb, cur_byte))
if (*cur_byte != *p)
return AVERROR_INVALIDDATA;
if (BETWEEN(*cur_byte | 32, 'a', 'z'))
return AVERROR_INVALIDDATA;
*result = i;
return 0;
}
return AVERROR_INVALIDDATA;
}
static int parse_int(AVIOContext *pb, int *cur_byte, int64_t *result)
{
int64_t val = 0;
skip_spaces(pb, cur_byte);
if ((unsigned)*cur_byte - '0' > 9)
return AVERROR_INVALIDDATA;
while (BETWEEN(*cur_byte, '0', '9')) {
val = val * 10 + (*cur_byte - '0');
next_byte(pb, cur_byte);
}
*result = val;
return 0;
}
static int parse_file(AVIOContext *pb, FFDemuxSubtitlesQueue *subs)
{
int ret, cur_byte, start_of_par;
AVBPrint label, content;
int64_t pos, start, duration;
AVPacket *pkt;
next_byte(pb, &cur_byte);
ret = expect_byte(pb, &cur_byte, '{');
if (ret < 0)
return AVERROR_INVALIDDATA;
ret = parse_label(pb, &cur_byte, &label);
if (ret < 0 || strcmp(label.str, "captions"))
return AVERROR_INVALIDDATA;
ret = expect_byte(pb, &cur_byte, '[');
if (ret < 0)
return AVERROR_INVALIDDATA;
while (1) {
content.size = 0;
start = duration = AV_NOPTS_VALUE;
ret = expect_byte(pb, &cur_byte, '{');
if (ret < 0)
return ret;
pos = avio_tell(pb) - 1;
while (1) {
ret = parse_label(pb, &cur_byte, &label);
if (ret < 0)
return ret;
if (!strcmp(label.str, "startOfParagraph")) {
ret = parse_boolean(pb, &cur_byte, &start_of_par);
if (ret < 0)
return ret;
} else if (!strcmp(label.str, "content")) {
ret = parse_string(pb, &cur_byte, &content, 1);
if (ret < 0)
return ret;
} else if (!strcmp(label.str, "startTime")) {
ret = parse_int(pb, &cur_byte, &start);
if (ret < 0)
return ret;
} else if (!strcmp(label.str, "duration")) {
ret = parse_int(pb, &cur_byte, &duration);
if (ret < 0)
return ret;
} else {
return AVERROR_INVALIDDATA;
}
skip_spaces(pb, &cur_byte);
if (cur_byte != ',')
break;
next_byte(pb, &cur_byte);
}
ret = expect_byte(pb, &cur_byte, '}');
if (ret < 0)
return ret;
if (!content.size || start == AV_NOPTS_VALUE ||
duration == AV_NOPTS_VALUE)
return AVERROR_INVALIDDATA;
pkt = ff_subtitles_queue_insert(subs, content.str, content.len, 0);
if (!pkt)
return AVERROR(ENOMEM);
pkt->pos = pos;
pkt->pts = start;
pkt->duration = duration;
av_bprint_finalize(&content, NULL);
skip_spaces(pb, &cur_byte);
if (cur_byte != ',')
break;
next_byte(pb, &cur_byte);
}
ret = expect_byte(pb, &cur_byte, ']');
if (ret < 0)
return ret;
ret = expect_byte(pb, &cur_byte, '}');
if (ret < 0)
return ret;
skip_spaces(pb, &cur_byte);
if (cur_byte != AVERROR_EOF)
return ERR_CODE(cur_byte);
return 0;
}
static av_cold int tedcaptions_read_header(AVFormatContext *avf)
{
TEDCaptionsDemuxer *tc = avf->priv_data;
AVStream *st;
int ret, i;
AVPacket *last;
ret = parse_file(avf->pb, &tc->subs);
if (ret < 0) {
if (ret == AVERROR_INVALIDDATA)
av_log(avf, AV_LOG_ERROR, "Syntax error near offset %"PRId64".\n",
avio_tell(avf->pb));
ff_subtitles_queue_clean(&tc->subs);
return ret;
}
ff_subtitles_queue_finalize(avf, &tc->subs);
for (i = 0; i < tc->subs.nb_subs; i++)
tc->subs.subs[i].pts += tc->start_time;
last = &tc->subs.subs[tc->subs.nb_subs - 1];
st = avformat_new_stream(avf, NULL);
if (!st)
return AVERROR(ENOMEM);
st->codecpar->codec_type = AVMEDIA_TYPE_SUBTITLE;
st->codecpar->codec_id = AV_CODEC_ID_TEXT;
avpriv_set_pts_info(st, 64, 1, 1000);
st->probe_packets = 0;
st->start_time = 0;
st->duration = last->pts + last->duration;
st->cur_dts = 0;
return 0;
}
static int tedcaptions_read_packet(AVFormatContext *avf, AVPacket *packet)
{
TEDCaptionsDemuxer *tc = avf->priv_data;
return ff_subtitles_queue_read_packet(&tc->subs, packet);
}
static int tedcaptions_read_close(AVFormatContext *avf)
{
TEDCaptionsDemuxer *tc = avf->priv_data;
ff_subtitles_queue_clean(&tc->subs);
return 0;
}
static av_cold int tedcaptions_read_probe(AVProbeData *p)
{
static const char *const tags[] = {
"\"captions\"", "\"duration\"", "\"content\"",
"\"startOfParagraph\"", "\"startTime\"",
};
unsigned i, count = 0;
const char *t;
if (p->buf[strspn(p->buf, " \t\r\n")] != '{')
return 0;
for (i = 0; i < FF_ARRAY_ELEMS(tags); i++) {
if (!(t = strstr(p->buf, tags[i])))
continue;
t += strlen(tags[i]);
t += strspn(t, " \t\r\n");
if (*t == ':')
count++;
}
return count == FF_ARRAY_ELEMS(tags) ? AVPROBE_SCORE_MAX :
count ? AVPROBE_SCORE_EXTENSION : 0;
}
static int tedcaptions_read_seek(AVFormatContext *avf, int stream_index,
int64_t min_ts, int64_t ts, int64_t max_ts,
int flags)
{
TEDCaptionsDemuxer *tc = avf->priv_data;
return ff_subtitles_queue_seek(&tc->subs, avf, stream_index,
min_ts, ts, max_ts, flags);
}
AVInputFormat ff_tedcaptions_demuxer = {
.name = "tedcaptions",
.long_name = NULL_IF_CONFIG_SMALL("TED Talks captions"),
.priv_data_size = sizeof(TEDCaptionsDemuxer),
.priv_class = &tedcaptions_demuxer_class,
.read_header = tedcaptions_read_header,
.read_packet = tedcaptions_read_packet,
.read_close = tedcaptions_read_close,
.read_probe = tedcaptions_read_probe,
.read_seek2 = tedcaptions_read_seek,
};
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