diff options
Diffstat (limited to 'libavcodec/movtextdec.c')
| -rw-r--r-- | libavcodec/movtextdec.c | 116 |
1 files changed, 116 insertions, 0 deletions
diff --git a/libavcodec/movtextdec.c b/libavcodec/movtextdec.c new file mode 100644 index 0000000000..05ff53afb4 --- /dev/null +++ b/libavcodec/movtextdec.c @@ -0,0 +1,116 @@ +/* + * 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" + +static int text_to_ass(AVBPrint *buf, const char *text, const char *text_end) +{ + while (text < text_end) { + switch (*text) { + case '\r': + break; + case '\n': + av_bprintf(buf, "\\N"); + break; + default: + av_bprint_chars(buf, *text, 1); + break; + } + text++; + } + + av_bprintf(buf, "\r\n"); + 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. + */ + 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; + int ts_start, ts_end; + AVBPrint buf; + const char *ptr = avpkt->data; + const char *end; + + 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. + */ + end = ptr + FFMIN(2 + AV_RB16(ptr), avpkt->size); + ptr += 2; + + ts_start = av_rescale_q(avpkt->pts, + avctx->time_base, + (AVRational){1,100}); + ts_end = av_rescale_q(avpkt->pts + avpkt->duration, + avctx->time_base, + (AVRational){1,100}); + + // Note that the spec recommends lines be no longer than 2048 characters. + av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED); + text_to_ass(&buf, ptr, end); + + if (!av_bprint_is_complete(&buf)) + return AVERROR(ENOMEM); + + ff_ass_add_rect(sub, buf.str, ts_start, ts_end-ts_start, 0); + *got_sub_ptr = sub->num_rects > 0; + av_bprint_finalize(&buf, NULL); + return avpkt->size; +} + +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, + .init = mov_text_init, + .decode = mov_text_decode_frame, +}; |