1/* 2 * copyright (c) 2008 Paul Kendall <paul@kcbbs.gen.nz> 3 * 4 * This file is part of Libav. 5 * 6 * Libav is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU Lesser General Public 8 * License as published by the Free Software Foundation; either 9 * version 2.1 of the License, or (at your option) any later version. 10 * 11 * Libav is distributed in the hope that it will be useful, 12 * but WITHOUT ANY WARRANTY; without even the implied warranty of 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 * Lesser General Public License for more details. 15 * 16 * You should have received a copy of the GNU Lesser General Public 17 * License along with Libav; if not, write to the Free Software 18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 19 */ 20 21/** 22 * @file 23 * AAC LATM parser 24 */ 25 26#include <stdint.h> 27#include "parser.h" 28 29#define LATM_HEADER 0x56e000 // 0x2b7 (11 bits) 30#define LATM_MASK 0xFFE000 // top 11 bits 31#define LATM_SIZE_MASK 0x001FFF // bottom 13 bits 32 33typedef struct LATMParseContext{ 34 ParseContext pc; 35 int count; 36} LATMParseContext; 37 38/** 39 * Find the end of the current frame in the bitstream. 40 * @return the position of the first byte of the next frame, or -1 41 */ 42static int latm_find_frame_end(AVCodecParserContext *s1, const uint8_t *buf, 43 int buf_size) 44{ 45 LATMParseContext *s = s1->priv_data; 46 ParseContext *pc = &s->pc; 47 int pic_found, i; 48 uint32_t state; 49 50 pic_found = pc->frame_start_found; 51 state = pc->state; 52 53 i = 0; 54 if (!pic_found) { 55 for (i = 0; i < buf_size; i++) { 56 state = (state<<8) | buf[i]; 57 if ((state & LATM_MASK) == LATM_HEADER) { 58 i++; 59 s->count = -i; 60 pic_found = 1; 61 break; 62 } 63 } 64 } 65 66 if (pic_found) { 67 /* EOF considered as end of frame */ 68 if (buf_size == 0) 69 return 0; 70 if ((state & LATM_SIZE_MASK) - s->count <= buf_size) { 71 pc->frame_start_found = 0; 72 pc->state = -1; 73 return (state & LATM_SIZE_MASK) - s->count; 74 } 75 } 76 77 s->count += buf_size; 78 pc->frame_start_found = pic_found; 79 pc->state = state; 80 81 return END_NOT_FOUND; 82} 83 84static int latm_parse(AVCodecParserContext *s1, AVCodecContext *avctx, 85 const uint8_t **poutbuf, int *poutbuf_size, 86 const uint8_t *buf, int buf_size) 87{ 88 LATMParseContext *s = s1->priv_data; 89 ParseContext *pc = &s->pc; 90 int next; 91 92 if (s1->flags & PARSER_FLAG_COMPLETE_FRAMES) { 93 next = buf_size; 94 } else { 95 next = latm_find_frame_end(s1, buf, buf_size); 96 97 if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) { 98 *poutbuf = NULL; 99 *poutbuf_size = 0; 100 return buf_size; 101 } 102 } 103 *poutbuf = buf; 104 *poutbuf_size = buf_size; 105 return next; 106} 107 108AVCodecParser ff_aac_latm_parser = { 109 .codec_ids = { CODEC_ID_AAC_LATM }, 110 .priv_data_size = sizeof(LATMParseContext), 111 .parser_parse = latm_parse, 112 .parser_close = ff_parse_close 113}; 114