yading@10: /*
yading@10:  * copyright (c) 2008 Paul Kendall <paul@kcbbs.gen.nz>
yading@10:  *
yading@10:  * This file is part of FFmpeg.
yading@10:  *
yading@10:  * FFmpeg is free software; you can redistribute it and/or
yading@10:  * modify it under the terms of the GNU Lesser General Public
yading@10:  * License as published by the Free Software Foundation; either
yading@10:  * version 2.1 of the License, or (at your option) any later version.
yading@10:  *
yading@10:  * FFmpeg is distributed in the hope that it will be useful,
yading@10:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
yading@10:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
yading@10:  * Lesser General Public License for more details.
yading@10:  *
yading@10:  * You should have received a copy of the GNU Lesser General Public
yading@10:  * License along with FFmpeg; if not, write to the Free Software
yading@10:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
yading@10:  */
yading@10: 
yading@10: /**
yading@10:  * @file
yading@10:  * AAC LATM parser
yading@10:  */
yading@10: 
yading@10: #include <stdint.h>
yading@10: #include "parser.h"
yading@10: 
yading@10: #define LATM_HEADER     0x56e000        // 0x2b7 (11 bits)
yading@10: #define LATM_MASK       0xFFE000        // top 11 bits
yading@10: #define LATM_SIZE_MASK  0x001FFF        // bottom 13 bits
yading@10: 
yading@10: typedef struct LATMParseContext{
yading@10:     ParseContext pc;
yading@10:     int count;
yading@10: } LATMParseContext;
yading@10: 
yading@10: /**
yading@10:  * Find the end of the current frame in the bitstream.
yading@10:  * @return the position of the first byte of the next frame, or -1
yading@10:  */
yading@10: static int latm_find_frame_end(AVCodecParserContext *s1, const uint8_t *buf,
yading@10:                                int buf_size)
yading@10: {
yading@10:     LATMParseContext *s = s1->priv_data;
yading@10:     ParseContext *pc    = &s->pc;
yading@10:     int pic_found, i;
yading@10:     uint32_t state;
yading@10: 
yading@10:     pic_found = pc->frame_start_found;
yading@10:     state     = pc->state;
yading@10: 
yading@10:     if (!pic_found) {
yading@10:         for (i = 0; i < buf_size; i++) {
yading@10:             state = (state<<8) | buf[i];
yading@10:             if ((state & LATM_MASK) == LATM_HEADER) {
yading@10:                 i++;
yading@10:                 s->count  = -i;
yading@10:                 pic_found = 1;
yading@10:                 break;
yading@10:             }
yading@10:         }
yading@10:     }
yading@10: 
yading@10:     if (pic_found) {
yading@10:         /* EOF considered as end of frame */
yading@10:         if (buf_size == 0)
yading@10:             return 0;
yading@10:         if ((state & LATM_SIZE_MASK) - s->count <= buf_size) {
yading@10:             pc->frame_start_found = 0;
yading@10:             pc->state             = -1;
yading@10:             return (state & LATM_SIZE_MASK) - s->count;
yading@10:         }
yading@10:     }
yading@10: 
yading@10:     s->count             += buf_size;
yading@10:     pc->frame_start_found = pic_found;
yading@10:     pc->state             = state;
yading@10: 
yading@10:     return END_NOT_FOUND;
yading@10: }
yading@10: 
yading@10: static int latm_parse(AVCodecParserContext *s1, AVCodecContext *avctx,
yading@10:                       const uint8_t **poutbuf, int *poutbuf_size,
yading@10:                       const uint8_t *buf, int buf_size)
yading@10: {
yading@10:     LATMParseContext *s = s1->priv_data;
yading@10:     ParseContext *pc    = &s->pc;
yading@10:     int next;
yading@10: 
yading@10:     if (s1->flags & PARSER_FLAG_COMPLETE_FRAMES) {
yading@10:         next = buf_size;
yading@10:     } else {
yading@10:         next = latm_find_frame_end(s1, buf, buf_size);
yading@10: 
yading@10:         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
yading@10:             *poutbuf      = NULL;
yading@10:             *poutbuf_size = 0;
yading@10:             return buf_size;
yading@10:         }
yading@10:     }
yading@10:     *poutbuf      = buf;
yading@10:     *poutbuf_size = buf_size;
yading@10:     return next;
yading@10: }
yading@10: 
yading@10: AVCodecParser ff_aac_latm_parser = {
yading@10:     .codec_ids      = { AV_CODEC_ID_AAC_LATM },
yading@10:     .priv_data_size = sizeof(LATMParseContext),
yading@10:     .parser_parse   = latm_parse,
yading@10:     .parser_close   = ff_parse_close
yading@10: };