Libav 0.7.1
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00001 /* 00002 * copyright (c) 2008 Paul Kendall <paul@kcbbs.gen.nz> 00003 * 00004 * This file is part of Libav. 00005 * 00006 * Libav is free software; you can redistribute it and/or 00007 * modify it under the terms of the GNU Lesser General Public 00008 * License as published by the Free Software Foundation; either 00009 * version 2.1 of the License, or (at your option) any later version. 00010 * 00011 * Libav is distributed in the hope that it will be useful, 00012 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00013 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 00014 * Lesser General Public License for more details. 00015 * 00016 * You should have received a copy of the GNU Lesser General Public 00017 * License along with Libav; if not, write to the Free Software 00018 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 00019 */ 00020 00026 #include <stdint.h> 00027 #include "parser.h" 00028 00029 #define LATM_HEADER 0x56e000 // 0x2b7 (11 bits) 00030 #define LATM_MASK 0xFFE000 // top 11 bits 00031 #define LATM_SIZE_MASK 0x001FFF // bottom 13 bits 00032 00033 typedef struct LATMParseContext{ 00034 ParseContext pc; 00035 int count; 00036 } LATMParseContext; 00037 00042 static int latm_find_frame_end(AVCodecParserContext *s1, const uint8_t *buf, 00043 int buf_size) 00044 { 00045 LATMParseContext *s = s1->priv_data; 00046 ParseContext *pc = &s->pc; 00047 int pic_found, i; 00048 uint32_t state; 00049 00050 pic_found = pc->frame_start_found; 00051 state = pc->state; 00052 00053 i = 0; 00054 if (!pic_found) { 00055 for (i = 0; i < buf_size; i++) { 00056 state = (state<<8) | buf[i]; 00057 if ((state & LATM_MASK) == LATM_HEADER) { 00058 i++; 00059 s->count = -i; 00060 pic_found = 1; 00061 break; 00062 } 00063 } 00064 } 00065 00066 if (pic_found) { 00067 /* EOF considered as end of frame */ 00068 if (buf_size == 0) 00069 return 0; 00070 if ((state & LATM_SIZE_MASK) - s->count <= buf_size) { 00071 pc->frame_start_found = 0; 00072 pc->state = -1; 00073 return (state & LATM_SIZE_MASK) - s->count; 00074 } 00075 } 00076 00077 s->count += buf_size; 00078 pc->frame_start_found = pic_found; 00079 pc->state = state; 00080 00081 return END_NOT_FOUND; 00082 } 00083 00084 static int latm_parse(AVCodecParserContext *s1, AVCodecContext *avctx, 00085 const uint8_t **poutbuf, int *poutbuf_size, 00086 const uint8_t *buf, int buf_size) 00087 { 00088 LATMParseContext *s = s1->priv_data; 00089 ParseContext *pc = &s->pc; 00090 int next; 00091 00092 if (s1->flags & PARSER_FLAG_COMPLETE_FRAMES) { 00093 next = buf_size; 00094 } else { 00095 next = latm_find_frame_end(s1, buf, buf_size); 00096 00097 if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) { 00098 *poutbuf = NULL; 00099 *poutbuf_size = 0; 00100 return buf_size; 00101 } 00102 } 00103 *poutbuf = buf; 00104 *poutbuf_size = buf_size; 00105 return next; 00106 } 00107 00108 AVCodecParser ff_aac_latm_parser = { 00109 { CODEC_ID_AAC_LATM }, 00110 sizeof(LATMParseContext), 00111 NULL, 00112 latm_parse, 00113 ff_parse_close 00114 };