/* * copyright (c) 2008 Paul Kendall <paul@kcbbs.gen.nz> * * 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 */ /** * @file * AAC LATM parser */ #include <stdint.h> #include "parser.h" #define LATM_HEADER 0x56e000 // 0x2b7 (11 bits) #define LATM_MASK 0xFFE000 // top 11 bits #define LATM_SIZE_MASK 0x001FFF // bottom 13 bits typedef struct LATMParseContext{ ParseContext pc; int count; } LATMParseContext; /** * finds the end of the current frame in the bitstream. * @return the position of the first byte of the next frame, or -1 */ static int latm_find_frame_end(AVCodecParserContext *s1, const uint8_t *buf, int buf_size) { LATMParseContext *s = s1->priv_data; ParseContext *pc = &s->pc; int pic_found, i; uint32_t state; pic_found = pc->frame_start_found; state = pc->state; i = 0; if (!pic_found) { for (i = 0; i < buf_size; i++) { state = (state<<8) | buf[i]; if ((state & LATM_MASK) == LATM_HEADER) { i++; s->count = -i; pic_found = 1; break; } } } if (pic_found) { /* EOF considered as end of frame */ if (buf_size == 0) return 0; if ((state & LATM_SIZE_MASK) - s->count <= buf_size) { pc->frame_start_found = 0; pc->state = -1; return (state & LATM_SIZE_MASK) - s->count; } } s->count += buf_size; pc->frame_start_found = pic_found; pc->state = state; return END_NOT_FOUND; } static int latm_parse(AVCodecParserContext *s1, AVCodecContext *avctx, const uint8_t **poutbuf, int *poutbuf_size, const uint8_t *buf, int buf_size) { LATMParseContext *s = s1->priv_data; ParseContext *pc = &s->pc; int next; if (s1->flags & PARSER_FLAG_COMPLETE_FRAMES) { next = buf_size; } else { next = latm_find_frame_end(s1, buf, buf_size); if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) { *poutbuf = NULL; *poutbuf_size = 0; return buf_size; } } *poutbuf = buf; *poutbuf_size = buf_size; return next; } AVCodecParser ff_aac_latm_parser = { { CODEC_ID_AAC_LATM }, sizeof(LATMParseContext), NULL, latm_parse, ff_parse_close };