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117 lines
3.7 KiB
C
117 lines
3.7 KiB
C
/*
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* 3GPP TS 26.245 Timed Text decoder
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* Copyright (c) 2012 Philip Langdale <philipl@overt.org>
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "avcodec.h"
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#include "ass.h"
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#include "libavutil/avstring.h"
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#include "libavutil/common.h"
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#include "libavutil/bprint.h"
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#include "libavutil/intreadwrite.h"
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static int text_to_ass(AVBPrint *buf, const char *text, const char *text_end)
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{
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while (text < text_end) {
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switch (*text) {
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case '\r':
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break;
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case '\n':
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av_bprintf(buf, "\\N");
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break;
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default:
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av_bprint_chars(buf, *text, 1);
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break;
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}
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text++;
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}
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av_bprintf(buf, "\r\n");
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return 0;
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}
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static int mov_text_init(AVCodecContext *avctx) {
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/*
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* TODO: Handle the default text style.
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* NB: Most players ignore styles completely, with the result that
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* it's very common to find files where the default style is broken
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* and respecting it results in a worse experience than ignoring it.
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*/
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return ff_ass_subtitle_header_default(avctx);
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}
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static int mov_text_decode_frame(AVCodecContext *avctx,
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void *data, int *got_sub_ptr, AVPacket *avpkt)
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{
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AVSubtitle *sub = data;
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int ts_start, ts_end;
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AVBPrint buf;
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const char *ptr = avpkt->data;
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const char *end;
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if (!ptr || avpkt->size < 2)
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return AVERROR_INVALIDDATA;
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/*
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* A packet of size two with value zero is an empty subtitle
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* used to mark the end of the previous non-empty subtitle.
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* We can just drop them here as we have duration information
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* already. If the value is non-zero, then it's technically a
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* bad packet.
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*/
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if (avpkt->size == 2)
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return AV_RB16(ptr) == 0 ? 0 : AVERROR_INVALIDDATA;
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/*
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* The first two bytes of the packet are the length of the text string
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* In complex cases, there are style descriptors appended to the string
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* so we can't just assume the packet size is the string size.
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*/
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end = ptr + FFMIN(2 + AV_RB16(ptr), avpkt->size);
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ptr += 2;
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ts_start = av_rescale_q(avpkt->pts,
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avctx->time_base,
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(AVRational){1,100});
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ts_end = av_rescale_q(avpkt->pts + avpkt->duration,
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avctx->time_base,
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(AVRational){1,100});
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// Note that the spec recommends lines be no longer than 2048 characters.
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av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);
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text_to_ass(&buf, ptr, end);
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if (!av_bprint_is_complete(&buf))
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return AVERROR(ENOMEM);
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ff_ass_add_rect(sub, buf.str, ts_start, ts_end-ts_start, 0);
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*got_sub_ptr = sub->num_rects > 0;
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av_bprint_finalize(&buf, NULL);
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return avpkt->size;
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}
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AVCodec ff_movtext_decoder = {
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.name = "mov_text",
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.long_name = NULL_IF_CONFIG_SMALL("3GPP Timed Text subtitle"),
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.type = AVMEDIA_TYPE_SUBTITLE,
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.id = AV_CODEC_ID_MOV_TEXT,
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.init = mov_text_init,
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.decode = mov_text_decode_frame,
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};
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