static int mov_text_decode_frame(AVCodecContext *avctx, void *data, int *got_sub_ptr, AVPacket *avpkt) { AVSubtitle *sub = data; MovTextContext *m = avctx->priv_data; int ret; AVBPrint buf; char *ptr = avpkt->data; char *end; int text_length, tsmb_type, ret_tsmb; uint64_t tsmb_size; const uint8_t *tsmb; 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. */ text_length = AV_RB16(ptr); end = ptr + FFMIN(2 + text_length, avpkt->size); ptr += 2; tsmb_size = 0; m->tracksize = 2 + text_length; m->style_entries = 0; m->box_flags = 0; m->count_s = 0; // Note that the spec recommends lines be no longer than 2048 characters. av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED); if (text_length + 2 != avpkt->size) { while (m->tracksize + 8 <= avpkt->size) { // A box is a minimum of 8 bytes. tsmb = ptr + m->tracksize - 2; tsmb_size = AV_RB32(tsmb); tsmb += 4; tsmb_type = AV_RB32(tsmb); tsmb += 4; if (tsmb_size == 1) { if (m->tracksize + 16 > avpkt->size) break; tsmb_size = AV_RB64(tsmb); tsmb += 8; m->size_var = 16; } else m->size_var = 8; //size_var is equal to 8 or 16 depending on the size of box if (tsmb_size == 0) { av_log(avctx, AV_LOG_ERROR, "tsmb_size is 0\n"); return AVERROR_INVALIDDATA; } if (tsmb_size > avpkt->size - m->tracksize) break; for (size_t i = 0; i < box_count; i++) { if (tsmb_type == box_types[i].type) { if (m->tracksize + m->size_var + box_types[i].base_size > avpkt->size) break; ret_tsmb = box_types[i].decode(tsmb, m, avpkt); if (ret_tsmb == -1) break; } } m->tracksize = m->tracksize + tsmb_size; } text_to_ass(&buf, ptr, end, m); } else text_to_ass(&buf, ptr, end, m); ret = ff_ass_add_rect(sub, buf.str, m->readorder++, 0, NULL, NULL); av_bprint_finalize(&buf, NULL); if (ret < 0) return ret; *got_sub_ptr = sub->num_rects > 0; return avpkt->size; }