parser.c

arm平台下的H264编码和解码源代码

/*
 * 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
#include "avcodec.h"
#include "mpegvideo.h"
#include "mpegaudio.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;

    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)
            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;
        }
    }
    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->cur_offset == 0) {
            s->last_pts = pts;
            s->last_dts = dts;
        }
    }

    /* WARNING: the returned index can be negative */
    index = s->parser->parser_parse(s, avctx, poutbuf, poutbuf_size, buf, buf_size);
    /* 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];
    }
    if (index < 0)
        index = 0;
    s->cur_offset += index;
    return index;
}

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{
    uint8_t *buffer;
    int index;
    int last_index;
    int buffer_size;
    uint32_t state;             ///< contains the last few bytes in MSB order
    int frame_start_found;
    int overread;               ///< the number of bytes which where irreversibly read from the next frame
    int overread_index;         ///< the index into ParseContext1.buffer of the overreaded bytes

    /* 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
 */
static int ff_combine_frame1(ParseContext1 *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++];
    }
    
    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;
}

/**
 * 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 mpeg1_find_frame_end(ParseContext1 *pc, const uint8_t *buf, int buf_size)
{
    int i;
    uint32_t state;
    
    state= pc->state;
    
    i=0;
    if(!pc->frame_start_found){
        for(i=0; i<buf_size; i++){
            state= (state<<8) | buf[i];
            if(state >= SLICE_MIN_START_CODE && state <= SLICE_MAX_START_CODE){
                i++;
                pc->frame_start_found=1;
                break;
            }
        }
    }
    
    if(pc->frame_start_found){
        /* EOF considered as end of frame */
        if (buf_size == 0)
            return 0;
        for(; i<buf_size; i++){
            state= (state<<8) | buf[i];
            if((state&0xFFFFFF00) == 0x100){
                if(state < SLICE_MIN_START_CODE || state > SLICE_MAX_START_CODE){
                    pc->frame_start_found=0;
                    pc->state=-1; 
                    return i-3;
                }
            }
        }
    }        
    pc->state= state;
    return END_NOT_FOUND;
}

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;
}

/* XXX: merge with libavcodec ? */
#define MPEG1_FRAME_RATE_BASE 1001

static const int frame_rate_tab[16] = {
        0,        
    24000,
    24024,
    25025,
    30000,
    30030,
    50050,
    60000,
    60060,
  // Xing's 15fps: (9)
    15015,
  // libmpeg3's "Unofficial economy rates": (10-13)
     5005,
    10010,
    12012,
    15015,
  // random, just to avoid segfault !never encode these
    25025,
    25025,
};

static void mpegvideo_extract_headers(AVCodecParserContext *s, 
                                      AVCodecContext *avctx,
                                      const uint8_t *buf, int buf_size)
{
    ParseContext1 *pc = s->priv_data;
    const uint8_t *buf_end;
    int32_t start_code;
    int frame_rate_index, ext_type, bytes_left;
    int frame_rate_ext_n, frame_rate_ext_d;
    int top_field_first, repeat_first_field, progressive_frame;
    int horiz_size_ext, vert_size_ext;

    s->repeat_pict = 0;
    buf_end = buf + buf_size;
    while (buf < buf_end) {
        start_code = find_start_code(&buf, buf_end);
        bytes_left = buf_end - buf;
        switch(start_code) {
        case PICTURE_START_CODE:
            if (bytes_left >= 2) {
                s->pict_type = (buf[1] >> 3) & 7;
            }
            break;
        case SEQ_START_CODE:
            if (bytes_left >= 4) {
                pc->width = avctx->width = (buf[0] << 4) | (buf[1] >> 4);
                pc->height = avctx->height = ((buf[1] & 0x0f) << 8) | buf[2];
                frame_rate_index = buf[3] & 0xf;
                pc->frame_rate = avctx->frame_rate = frame_rate_tab[frame_rate_index];
                avctx->frame_rate_base = MPEG1_FRAME_RATE_BASE;
                avctx->codec_id = CODEC_ID_MPEG1VIDEO;
                avctx->sub_id = 1;
            }
            break;
        case EXT_START_CODE:
            if (bytes_left >= 1) {
                ext_type = (buf[0] >> 4);
                switch(ext_type) {
                case 0x1: /* sequence extension */
                    if (bytes_left >= 6) {
                        horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
                        vert_size_ext = (buf[2] >> 5) & 3;
                        frame_rate_ext_n = (buf[5] >> 5) & 3;
                        frame_rate_ext_d = (buf[5] & 0x1f);
                        pc->progressive_sequence = buf[1] & (1 << 3);

                        avctx->width = pc->width | (horiz_size_ext << 12);
                        avctx->height = pc->height | (vert_size_ext << 12);
                        avctx->frame_rate = pc->frame_rate * (frame_rate_ext_n + 1);
                        avctx->frame_rate_base = MPEG1_FRAME_RATE_BASE * (frame_rate_ext_d + 1);
                        avctx->codec_id = CODEC_ID_MPEG2VIDEO;
                        avctx->sub_id = 2; /* forces MPEG2 */
                    }
                    break;
                case 0x8: /* picture coding extension */
                    if (bytes_left >= 5) {
                        top_field_first = buf[3] & (1 << 7);
                        repeat_first_field = buf[3] & (1 << 1);
                        progressive_frame = buf[4] & (1 << 7);
                    
                        /* check if we must repeat the frame */
                        if (repeat_first_field) {
                            if (pc->progressive_sequence) {
                                if (top_field_first)
                                    s->repeat_pict = 4;
                                else
                                    s->repeat_pict = 2;
                            } else if (progressive_frame) {
                                s->repeat_pict = 1;
                            }
                        }
                    }
                    break;
                }
            }
            break;
        case -1:
            goto the_end;
        default:
            /* we stop parsing when we encounter a slice. It ensures
               that this function takes a negligible amount of time */
            if (start_code >= SLICE_MIN_START_CODE && 
                start_code <= SLICE_MAX_START_CODE)
                goto the_end;
            break;
        }
    }
 the_end: ;
}

static int mpegvideo_parse(AVCodecParserContext *s,
                           AVCodecContext *avctx,
                           uint8_t **poutbuf, int *poutbuf_size, 
                           const uint8_t *buf, int buf_size)
{
    ParseContext1 *pc = s->priv_data;
    int next;
    
    next= mpeg1_find_frame_end(pc, buf, buf_size);
    
    if (ff_combine_frame1(pc, next, (uint8_t **)&buf, &buf_size) < 0) {
        *poutbuf = NULL;
        *poutbuf_size = 0;
        return buf_size;
    }
    /* we have a full frame : we just parse the first few MPEG headers
       to have the full timing information. The time take by this
       function should be negligible for uncorrupted streams */
    mpegvideo_extract_headers(s, avctx, buf, buf_size);
#if 0
    printf("pict_type=%d frame_rate=%0.3f repeat_pict=%d\n", 
           s->pict_type, (double)avctx->frame_rate / avctx->frame_rate_base, s->repeat_pict);
#endif

    *poutbuf = (uint8_t *)buf;
    *poutbuf_size = buf_size;
    return next;
}

static void mpegvideo_parse_close(AVCodecParserContext *s)
{
    ParseContext1 *pc = s->priv_data;

    av_free(pc->buffer);
    av_free(pc->enc);
}

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

/**
 * 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 mpeg4_find_frame_end(ParseContext1 *pc, 
                                const uint8_t *buf, int buf_size)
{
    int vop_found, i;
    uint32_t state;
    
    vop_found= pc->frame_start_found;
    state= pc->state;
    
    i=0;
    if(!vop_found){
        for(i=0; i<buf_size; i++){
            state= (state<<8) | buf[i];
            if(state == 0x1B6){
                i++;
                vop_found=1;
                break;
            }
        }
    }

    if(vop_found){    
        /* EOF considered as end of frame */
        if (buf_size == 0)
            return 0;
        for(; i<buf_size; i++){
            state= (state<<8) | buf[i];
            if((state&0xFFFFFF00) == 0x100){
                pc->frame_start_found=0;
                pc->state=-1; 
                return i-3;
            }
        }
    }
    pc->frame_start_found= vop_found;