| 1 | /* |
| 2 | * 3GPP TS 26.245 Timed Text decoder |
| 3 | * Copyright (c) 2012 Philip Langdale <philipl@overt.org> |
| 4 | * |
| 5 | * This file is part of FFmpeg. |
| 6 | * |
| 7 | * FFmpeg is free software; you can redistribute it and/or |
| 8 | * modify it under the terms of the GNU Lesser General Public |
| 9 | * License as published by the Free Software Foundation; either |
| 10 | * version 2.1 of the License, or (at your option) any later version. |
| 11 | * |
| 12 | * FFmpeg is distributed in the hope that it will be useful, |
| 13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 15 | * Lesser General Public License for more details. |
| 16 | * |
| 17 | * You should have received a copy of the GNU Lesser General Public |
| 18 | * License along with FFmpeg; if not, write to the Free Software |
| 19 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| 20 | */ |
| 21 | |
| 22 | #include "avcodec.h" |
| 23 | #include "ass.h" |
| 24 | #include "libavutil/avstring.h" |
| 25 | #include "libavutil/common.h" |
| 26 | #include "libavutil/bprint.h" |
| 27 | #include "libavutil/intreadwrite.h" |
| 28 | |
| 29 | static int text_to_ass(AVBPrint *buf, const char *text, const char *text_end) |
| 30 | { |
| 31 | while (text < text_end) { |
| 32 | switch (*text) { |
| 33 | case '\r': |
| 34 | break; |
| 35 | case '\n': |
| 36 | av_bprintf(buf, "\\N"); |
| 37 | break; |
| 38 | default: |
| 39 | av_bprint_chars(buf, *text, 1); |
| 40 | break; |
| 41 | } |
| 42 | text++; |
| 43 | } |
| 44 | |
| 45 | return 0; |
| 46 | } |
| 47 | |
| 48 | static int mov_text_init(AVCodecContext *avctx) { |
| 49 | /* |
| 50 | * TODO: Handle the default text style. |
| 51 | * NB: Most players ignore styles completely, with the result that |
| 52 | * it's very common to find files where the default style is broken |
| 53 | * and respecting it results in a worse experience than ignoring it. |
| 54 | */ |
| 55 | return ff_ass_subtitle_header_default(avctx); |
| 56 | } |
| 57 | |
| 58 | static int mov_text_decode_frame(AVCodecContext *avctx, |
| 59 | void *data, int *got_sub_ptr, AVPacket *avpkt) |
| 60 | { |
| 61 | AVSubtitle *sub = data; |
| 62 | int ret, ts_start, ts_end; |
| 63 | AVBPrint buf; |
| 64 | const char *ptr = avpkt->data; |
| 65 | const char *end; |
| 66 | |
| 67 | if (!ptr || avpkt->size < 2) |
| 68 | return AVERROR_INVALIDDATA; |
| 69 | |
| 70 | /* |
| 71 | * A packet of size two with value zero is an empty subtitle |
| 72 | * used to mark the end of the previous non-empty subtitle. |
| 73 | * We can just drop them here as we have duration information |
| 74 | * already. If the value is non-zero, then it's technically a |
| 75 | * bad packet. |
| 76 | */ |
| 77 | if (avpkt->size == 2) |
| 78 | return AV_RB16(ptr) == 0 ? 0 : AVERROR_INVALIDDATA; |
| 79 | |
| 80 | /* |
| 81 | * The first two bytes of the packet are the length of the text string |
| 82 | * In complex cases, there are style descriptors appended to the string |
| 83 | * so we can't just assume the packet size is the string size. |
| 84 | */ |
| 85 | end = ptr + FFMIN(2 + AV_RB16(ptr), avpkt->size); |
| 86 | ptr += 2; |
| 87 | |
| 88 | ts_start = av_rescale_q(avpkt->pts, |
| 89 | avctx->time_base, |
| 90 | (AVRational){1,100}); |
| 91 | ts_end = av_rescale_q(avpkt->pts + avpkt->duration, |
| 92 | avctx->time_base, |
| 93 | (AVRational){1,100}); |
| 94 | |
| 95 | // Note that the spec recommends lines be no longer than 2048 characters. |
| 96 | av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED); |
| 97 | text_to_ass(&buf, ptr, end); |
| 98 | ret = ff_ass_add_rect_bprint(sub, &buf, ts_start, ts_end-ts_start); |
| 99 | av_bprint_finalize(&buf, NULL); |
| 100 | if (ret < 0) |
| 101 | return ret; |
| 102 | *got_sub_ptr = sub->num_rects > 0; |
| 103 | return avpkt->size; |
| 104 | } |
| 105 | |
| 106 | AVCodec ff_movtext_decoder = { |
| 107 | .name = "mov_text", |
| 108 | .long_name = NULL_IF_CONFIG_SMALL("3GPP Timed Text subtitle"), |
| 109 | .type = AVMEDIA_TYPE_SUBTITLE, |
| 110 | .id = AV_CODEC_ID_MOV_TEXT, |
| 111 | .init = mov_text_init, |
| 112 | .decode = mov_text_decode_frame, |
| 113 | }; |