parser.c

mpeg4 video codec mpeg4 video codec

/*
 * Audio and Video frame extraction
 * Copyright (c) 2003 Fabrice Bellard.
 * Copyright (c) 2003 Michael Niedermayer.
 *
 * This library 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 of the License, or (at your option) any later version.
 *
 * This library 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 this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */
#include "avcodec.h"
#include "mpegvideo.h"

AVCodecParser *av_first_parser = NULL;

void av_register_codec_parser(AVCodecParser *parser)
{
    parser->next = av_first_parser;
    av_first_parser = parser;
}

AVCodecParserContext *av_parser_init(int codec_id)
{
    AVCodecParserContext *s;
    AVCodecParser *parser;
    int ret;

    if(codec_id == CODEC_ID_NONE)
        return NULL;

    for(parser = av_first_parser; parser != NULL; parser = parser->next) {
        if (parser->codec_ids[0] == codec_id ||
            parser->codec_ids[1] == codec_id ||
            parser->codec_ids[2] == codec_id ||
            parser->codec_ids[3] == codec_id ||
            parser->codec_ids[4] == codec_id)
            goto found;
    }
    return NULL;
 found:
    s = av_mallocz(sizeof(AVCodecParserContext));
    if (!s)
        return NULL;
    s->parser = parser;
    s->priv_data = av_mallocz(parser->priv_data_size);
    if (!s->priv_data) {
        av_free(s);
        return NULL;
    }
    if (parser->parser_init) {
        ret = parser->parser_init(s);
        if (ret != 0) {
            av_free(s->priv_data);
            av_free(s);
            return NULL;
        }
    }
    s->fetch_timestamp=1;
    return s;
}

/* NOTE: buf_size == 0 is used to signal EOF so that the last frame
   can be returned if necessary */
int av_parser_parse(AVCodecParserContext *s, 
                    AVCodecContext *avctx,
                    uint8_t **poutbuf, int *poutbuf_size, 
                    const uint8_t *buf, int buf_size,
                    int64_t pts, int64_t dts)
{
    int index, i, k;
    uint8_t dummy_buf[FF_INPUT_BUFFER_PADDING_SIZE];
    
    if (buf_size == 0) {
        /* padding is always necessary even if EOF, so we add it here */
        memset(dummy_buf, 0, sizeof(dummy_buf));
        buf = dummy_buf;
    } else {
        /* add a new packet descriptor */
        k = (s->cur_frame_start_index + 1) & (AV_PARSER_PTS_NB - 1);
        s->cur_frame_start_index = k;
        s->cur_frame_offset[k] = s->cur_offset;
        s->cur_frame_pts[k] = pts;
        s->cur_frame_dts[k] = dts;

        /* fill first PTS/DTS */
        if (s->fetch_timestamp){
            s->fetch_timestamp=0;
            s->last_pts = pts;
            s->last_dts = dts;
            s->cur_frame_pts[k] =
            s->cur_frame_dts[k] = AV_NOPTS_VALUE;
        }
    }

    /* WARNING: the returned index can be negative */
    index = s->parser->parser_parse(s, avctx, poutbuf, poutbuf_size, buf, buf_size);
//av_log(NULL, AV_LOG_DEBUG, "parser: in:%lld, %lld, out:%lld, %lld, in:%d out:%d id:%d\n", pts, dts, s->last_pts, s->last_dts, buf_size, *poutbuf_size, avctx->codec_id);
    /* update the file pointer */
    if (*poutbuf_size) {
        /* fill the data for the current frame */
        s->frame_offset = s->last_frame_offset;
        s->pts = s->last_pts;
        s->dts = s->last_dts;
        
        /* offset of the next frame */
        s->last_frame_offset = s->cur_offset + index;
        /* find the packet in which the new frame starts. It
           is tricky because of MPEG video start codes
           which can begin in one packet and finish in
           another packet. In the worst case, an MPEG
           video start code could be in 4 different
           packets. */
        k = s->cur_frame_start_index;
        for(i = 0; i < AV_PARSER_PTS_NB; i++) {
            if (s->last_frame_offset >= s->cur_frame_offset[k])
                break;
            k = (k - 1) & (AV_PARSER_PTS_NB - 1);
        }

        s->last_pts = s->cur_frame_pts[k];
        s->last_dts = s->cur_frame_dts[k];
        
        /* some parsers tell us the packet size even before seeing the first byte of the next packet,
           so the next pts/dts is in the next chunk */
        if(index == buf_size){
            s->fetch_timestamp=1;
        }
    }
    if (index < 0)
        index = 0;
    s->cur_offset += index;
    return index;
}

/**
 *
 * @return 0 if the output buffer is a subset of the input, 1 if it is allocated and must be freed
 */
int av_parser_change(AVCodecParserContext *s,
                     AVCodecContext *avctx,
                     uint8_t **poutbuf, int *poutbuf_size,
                     const uint8_t *buf, int buf_size, int keyframe){

    if(s && s->parser->split){
        if((avctx->flags & CODEC_FLAG_GLOBAL_HEADER) || (avctx->flags2 & CODEC_FLAG2_LOCAL_HEADER)){
            int i= s->parser->split(avctx, buf, buf_size);
            buf += i;
            buf_size -= i;
        }
    }

    /* cast to avoid warning about discarding qualifiers */
    *poutbuf= (uint8_t *) buf;
    *poutbuf_size= buf_size;
    if(avctx->extradata){
        if(  (keyframe && (avctx->flags2 & CODEC_FLAG2_LOCAL_HEADER))
            /*||(s->pict_type != I_TYPE && (s->flags & PARSER_FLAG_DUMP_EXTRADATA_AT_NOKEY))*/
            /*||(? && (s->flags & PARSER_FLAG_DUMP_EXTRADATA_AT_BEGIN)*/){
            int size= buf_size + avctx->extradata_size;
            *poutbuf_size= size;
            *poutbuf= av_malloc(size + FF_INPUT_BUFFER_PADDING_SIZE);

            memcpy(*poutbuf, avctx->extradata, avctx->extradata_size);
            memcpy((*poutbuf) + avctx->extradata_size, buf, buf_size + FF_INPUT_BUFFER_PADDING_SIZE);
            return 1;
        }
    }

    return 0;
}

void av_parser_close(AVCodecParserContext *s)
{
    if (s->parser->parser_close)
        s->parser->parser_close(s);
    av_free(s->priv_data);
    av_free(s);
}

/*****************************************************/

//#define END_NOT_FOUND (-100)

#define PICTURE_START_CODE	0x00000100
#define SEQ_START_CODE		0x000001b3
#define EXT_START_CODE		0x000001b5
#define SLICE_MIN_START_CODE	0x00000101
#define SLICE_MAX_START_CODE	0x000001af

typedef struct ParseContext1{
    ParseContext pc;
/* XXX/FIXME PC1 vs. PC */
    /* MPEG2 specific */
    int frame_rate;
    int progressive_sequence;
    int width, height;

    /* XXX: suppress that, needed by MPEG4 */
    MpegEncContext *enc;
    int first_picture;
} ParseContext1;

/**
 * combines the (truncated) bitstream to a complete frame
 * @returns -1 if no complete frame could be created
 */
int ff_combine_frame(ParseContext *pc, int next, uint8_t **buf, int *buf_size)
{
#if 0
    if(pc->overread){
        printf("overread %d, state:%X next:%d index:%d o_index:%d\n", pc->overread, pc->state, next, pc->index, pc->overread_index);
        printf("%X %X %X %X\n", (*buf)[0], (*buf)[1],(*buf)[2],(*buf)[3]);
    }
#endif

    /* copy overreaded bytes from last frame into buffer */
    for(; pc->overread>0; pc->overread--){
        pc->buffer[pc->index++]= pc->buffer[pc->overread_index++];
    }
    
    /* flush remaining if EOF */
    if(!*buf_size && next == END_NOT_FOUND){
        next= 0;
    }

    pc->last_index= pc->index;

    /* copy into buffer end return */
    if(next == END_NOT_FOUND){
        pc->buffer= av_fast_realloc(pc->buffer, &pc->buffer_size, (*buf_size) + pc->index + FF_INPUT_BUFFER_PADDING_SIZE);

        memcpy(&pc->buffer[pc->index], *buf, *buf_size);
        pc->index += *buf_size;
        return -1;
    }

    *buf_size=
    pc->overread_index= pc->index + next;
    
    /* append to buffer */
    if(pc->index){
        pc->buffer= av_fast_realloc(pc->buffer, &pc->buffer_size, next + pc->index + FF_INPUT_BUFFER_PADDING_SIZE);

        memcpy(&pc->buffer[pc->index], *buf, next + FF_INPUT_BUFFER_PADDING_SIZE );
        pc->index = 0;
        *buf= pc->buffer;
    }

    /* store overread bytes */
    for(;next < 0; next++){
        pc->state = (pc->state<<8) | pc->buffer[pc->last_index + next];
        pc->overread++;
    }

#if 0
    if(pc->overread){
        printf("overread %d, state:%X next:%d index:%d o_index:%d\n", pc->overread, pc->state, next, pc->index, pc->overread_index);
        printf("%X %X %X %X\n", (*buf)[0], (*buf)[1],(*buf)[2],(*buf)[3]);
    }
#endif

    return 0;
}

static int find_start_code(const uint8_t **pbuf_ptr, const uint8_t *buf_end)
{
    const uint8_t *buf_ptr;
    unsigned int state=0xFFFFFFFF, v;
    int val;

    buf_ptr = *pbuf_ptr;
    while (buf_ptr < buf_end) {
        v = *buf_ptr++;
        if (state == 0x000001) {
            state = ((state << 8) | v) & 0xffffff;
            val = state;
            goto found;
        }
        state = ((state << 8) | v) & 0xffffff;
    }
    val = -1;
 found:
    *pbuf_ptr = buf_ptr;
    return val;
}