avidec.c

ffmpeg的完整源代码和作者自己写的文档。不但有在Linux的工程哦

/*
 * AVI demuxer
 * Copyright (c) 2001 Fabrice Bellard.
 *
 * 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
 */
#include "avformat.h"
#include "avi.h"
#include "dv.h"
#include "riff.h"

#undef NDEBUG
#include <assert.h>

//#define DEBUG
//#define DEBUG_SEEK

typedef struct AVIStream {
    int64_t frame_offset; /* current frame (video) or byte (audio) counter
                         (used to compute the pts) */
    int remaining;
    int packet_size;

    int scale;
    int rate;
    int sample_size; /* size of one sample (or packet) (in the rate/scale sense) in bytes */

    int64_t cum_len; /* temporary storage (used during seek) */

    int prefix;                       ///< normally 'd'<<8 + 'c' or 'w'<<8 + 'b'
    int prefix_count;
} AVIStream;

typedef struct {
    int64_t  riff_end;
    int64_t  movi_end;
    int64_t  fsize;
    offset_t movi_list;
    int index_loaded;
    int is_odml;
    int non_interleaved;
    int stream_index;
    DVDemuxContext* dv_demux;
} AVIContext;

static const char avi_headers[][8] = {
    { 'R', 'I', 'F', 'F',    'A', 'V', 'I', ' ' },
    { 'R', 'I', 'F', 'F',    'A', 'V', 'I', 'X' },
    { 'R', 'I', 'F', 'F',    'A', 'V', 'I', 0x19},
    { 'O', 'N', '2', ' ',    'O', 'N', '2', 'f' },
    { 'R', 'I', 'F', 'F',    'A', 'M', 'V', ' ' },
    { 0 }
};

static int avi_load_index(AVFormatContext *s);
static int guess_ni_flag(AVFormatContext *s);

#ifdef DEBUG
static void print_tag(const char *str, unsigned int tag, int size)
{
    printf("%s: tag=%c%c%c%c size=0x%x\n",
           str, tag & 0xff,
           (tag >> 8) & 0xff,
           (tag >> 16) & 0xff,
           (tag >> 24) & 0xff,
           size);
}
#endif

static int get_riff(AVIContext *avi, ByteIOContext *pb)
{
    char header[8];
    int i;

    /* check RIFF header */
    get_buffer(pb, header, 4);
    avi->riff_end = get_le32(pb);   /* RIFF chunk size */
    avi->riff_end += url_ftell(pb); /* RIFF chunk end */
    get_buffer(pb, header+4, 4);

    for(i=0; avi_headers[i][0]; i++)
        if(!memcmp(header, avi_headers[i], 8))
            break;
    if(!avi_headers[i][0])
        return -1;

    if(header[7] == 0x19)
        av_log(NULL, AV_LOG_INFO, "file has been generated with a totally broken muxer\n");

    return 0;
}

static int read_braindead_odml_indx(AVFormatContext *s, int frame_num){
    AVIContext *avi = s->priv_data;
    ByteIOContext *pb = &s->pb;
    int longs_pre_entry= get_le16(pb);
    int index_sub_type = get_byte(pb);
    int index_type     = get_byte(pb);
    int entries_in_use = get_le32(pb);
    int chunk_id       = get_le32(pb);
    int64_t base       = get_le64(pb);
    int stream_id= 10*((chunk_id&0xFF) - '0') + (((chunk_id>>8)&0xFF) - '0');
    AVStream *st;
    AVIStream *ast;
    int i;
    int64_t last_pos= -1;
    int64_t filesize= url_fsize(&s->pb);

#ifdef DEBUG_SEEK
    av_log(s, AV_LOG_ERROR, "longs_pre_entry:%d index_type:%d entries_in_use:%d chunk_id:%X base:%16"PRIX64"\n",
        longs_pre_entry,index_type, entries_in_use, chunk_id, base);
#endif

    if(stream_id > s->nb_streams || stream_id < 0)
        return -1;
    st= s->streams[stream_id];
    ast = st->priv_data;

    if(index_sub_type)
        return -1;

    get_le32(pb);

    if(index_type && longs_pre_entry != 2)
        return -1;
    if(index_type>1)
        return -1;

    if(filesize > 0 && base >= filesize){
        av_log(s, AV_LOG_ERROR, "ODML index invalid\n");
        if(base>>32 == (base & 0xFFFFFFFF) && (base & 0xFFFFFFFF) < filesize && filesize <= 0xFFFFFFFF)
            base &= 0xFFFFFFFF;
        else
            return -1;
    }

    for(i=0; i<entries_in_use; i++){
        if(index_type){
            int64_t pos= get_le32(pb) + base - 8;
            int len    = get_le32(pb);
            int key= len >= 0;
            len &= 0x7FFFFFFF;

#ifdef DEBUG_SEEK
            av_log(s, AV_LOG_ERROR, "pos:%"PRId64", len:%X\n", pos, len);
#endif
            if(last_pos == pos || pos == base - 8)
                avi->non_interleaved= 1;
            else
                av_add_index_entry(st, pos, ast->cum_len / FFMAX(1, ast->sample_size), len, 0, key ? AVINDEX_KEYFRAME : 0);

            if(ast->sample_size)
                ast->cum_len += len;
            else
                ast->cum_len ++;
            last_pos= pos;
        }else{
            int64_t offset, pos;
            int duration;
            offset = get_le64(pb);
            get_le32(pb);       /* size */
            duration = get_le32(pb);
            pos = url_ftell(pb);

            url_fseek(pb, offset+8, SEEK_SET);
            read_braindead_odml_indx(s, frame_num);
            frame_num += duration;

            url_fseek(pb, pos, SEEK_SET);
        }
    }
    avi->index_loaded=1;
    return 0;
}

static void clean_index(AVFormatContext *s){
    int i;
    int64_t j;

    for(i=0; i<s->nb_streams; i++){
        AVStream *st = s->streams[i];
        AVIStream *ast = st->priv_data;
        int n= st->nb_index_entries;
        int max= ast->sample_size;
        int64_t pos, size, ts;

        if(n != 1 || ast->sample_size==0)
            continue;

        while(max < 1024) max+=max;

        pos= st->index_entries[0].pos;
        size= st->index_entries[0].size;
        ts= st->index_entries[0].timestamp;

        for(j=0; j<size; j+=max){
            av_add_index_entry(st, pos+j, ts + j/ast->sample_size, FFMIN(max, size-j), 0, AVINDEX_KEYFRAME);
        }
    }
}

static int avi_read_tag(ByteIOContext *pb, char *buf, int maxlen,  unsigned int size)
{
    offset_t i = url_ftell(pb);
    size += (size & 1);
    get_strz(pb, buf, maxlen);
    url_fseek(pb, i+size, SEEK_SET);
    return 0;
}

static int avi_read_header(AVFormatContext *s, AVFormatParameters *ap)
{
    AVIContext *avi = s->priv_data;
    ByteIOContext *pb = &s->pb;
    uint32_t tag, tag1, handler;
    int codec_type, stream_index, frame_period, bit_rate;
    unsigned int size, nb_frames;
    int i;
    AVStream *st;
    AVIStream *ast = NULL;
    char str_track[4];
    int avih_width=0, avih_height=0;
    int amv_file_format=0;

    avi->stream_index= -1;

    if (get_riff(avi, pb) < 0)
        return -1;

    avi->fsize = url_fsize(pb);
    if(avi->fsize<=0)
        avi->fsize= avi->riff_end;

    /* first list tag */
    stream_index = -1;
    codec_type = -1;
    frame_period = 0;
    for(;;) {
        if (url_feof(pb))
            goto fail;
        tag = get_le32(pb);
        size = get_le32(pb);
#ifdef DEBUG
        print_tag("tag", tag, size);
#endif

        switch(tag) {
        case MKTAG('L', 'I', 'S', 'T'):
            /* ignored, except when start of video packets */
            tag1 = get_le32(pb);
#ifdef DEBUG
            print_tag("list", tag1, 0);
#endif
            if (tag1 == MKTAG('m', 'o', 'v', 'i')) {
                avi->movi_list = url_ftell(pb) - 4;
                if(size) avi->movi_end = avi->movi_list + size + (size & 1);
                else     avi->movi_end = url_fsize(pb);
#ifdef DEBUG
                printf("movi end=%"PRIx64"\n", avi->movi_end);
#endif
                goto end_of_header;
            }
            break;
        case MKTAG('d', 'm', 'l', 'h'):
            avi->is_odml = 1;
            url_fskip(pb, size + (size & 1));
            break;
        case MKTAG('a', 'm', 'v', 'h'):
            amv_file_format=1;
        case MKTAG('a', 'v', 'i', 'h'):
            /* avi header */
            /* using frame_period is bad idea */
            frame_period = get_le32(pb);
            bit_rate = get_le32(pb) * 8;
            get_le32(pb);
            avi->non_interleaved |= get_le32(pb) & AVIF_MUSTUSEINDEX;

            url_fskip(pb, 2 * 4);
            get_le32(pb);
            get_le32(pb);
            avih_width=get_le32(pb);
            avih_height=get_le32(pb);

            url_fskip(pb, size - 10 * 4);
            break;
        case MKTAG('s', 't', 'r', 'h'):
            /* stream header */

            tag1 = get_le32(pb);
            handler = get_le32(pb); /* codec tag */

            if(tag1 == MKTAG('p', 'a', 'd', 's')){
                url_fskip(pb, size - 8);
                break;
            }else{
                stream_index++;
                st = av_new_stream(s, stream_index);
                if (!st)
                    goto fail;

                ast = av_mallocz(sizeof(AVIStream));
                if (!ast)
                    goto fail;
                st->priv_data = ast;
            }
            if(amv_file_format)
                tag1 = stream_index ? MKTAG('a','u','d','s') : MKTAG('v','i','d','s');

#ifdef DEBUG
            print_tag("strh", tag1, -1);
#endif
            if(tag1 == MKTAG('i', 'a', 'v', 's') || tag1 == MKTAG('i', 'v', 'a', 's')){
                int64_t dv_dur;

                /*
                 * After some consideration -- I don't think we
                 * have to support anything but DV in a type1 AVIs.
                 */
                if (s->nb_streams != 1)
                    goto fail;

                if (handler != MKTAG('d', 'v', 's', 'd') &&
                    handler != MKTAG('d', 'v', 'h', 'd') &&
                    handler != MKTAG('d', 'v', 's', 'l'))
                   goto fail;

                ast = s->streams[0]->priv_data;
                av_freep(&s->streams[0]->codec->extradata);
                av_freep(&s->streams[0]);
                s->nb_streams = 0;
                if (ENABLE_DV_DEMUXER) {
                    avi->dv_demux = dv_init_demux(s);
                    if (!avi->dv_demux)
                        goto fail;
                }
                s->streams[0]->priv_data = ast;
                url_fskip(pb, 3 * 4);
                ast->scale = get_le32(pb);