PeerStreamer

/*

 * 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 aac_latm_parser = {

    { CODEC_ID_AAC_LATM },

    sizeof(LATMParseContext),

    NULL,

    latm_parse,

    ff_parse_close

};