avidec.c

ffmpeg源码分析

/*
 * AVI decoder.
 * Copyright (c) 2001 Fabrice Bellard.
 *
 * 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 "avformat.h"
#include "avi.h"
#include "dv.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;
    offset_t movi_list;
    int index_loaded;
    int is_odml;
    int non_interleaved;
    int stream_index;
    DVDemuxContext* dv_demux;
} AVIContext;

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)
{
    uint32_t tag;
    /* check RIFF header */
    tag = get_le32(pb);

    if (tag != MKTAG('R', 'I', 'F', 'F'))
        return -1;
    avi->riff_end = get_le32(pb);   /* RIFF chunk size */
    avi->riff_end += url_ftell(pb); /* RIFF chunk end */
    tag = get_le32(pb);
    if (tag != MKTAG('A', 'V', 'I', ' ') && tag != MKTAG('A', 'V', 'I', 'X'))
        return -1;

    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;

//    av_log(s, AV_LOG_ERROR, "longs_pre_entry:%d index_type:%d entries_in_use:%d chunk_id:%X base:%Ld\n",
//        longs_pre_entry,index_type, entries_in_use, chunk_id, base);

    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;

    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;

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

            if(ast->sample_size)
                ast->cum_len += len / ast->sample_size;
            else
                ast->cum_len ++;
            last_pos= pos;
        }else{
            int64_t offset= get_le64(pb);
            int size      = get_le32(pb);
            int duration  = get_le32(pb);
            int64_t 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);
        }
    }
    return 0;
}

static void clean_index(AVFormatContext *s){
    int i, 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_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, n;
    AVStream *st;
    AVIStream *ast;
    int xan_video = 0;  /* hack to support Xan A/V */

    avi->stream_index= -1;

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

    /* 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;
                else     avi->movi_end = url_fsize(pb);
#ifdef DEBUG
                printf("movi end=%Lx\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', '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);
            n = get_le32(pb);
            for(i=0;i<n;i++) {
                AVIStream *ast;
                st = av_new_stream(s, i);
                if (!st)
                    goto fail;

                ast = av_mallocz(sizeof(AVIStream));
                if (!ast)
                    goto fail;
                st->priv_data = ast;
            }
            url_fskip(pb, size - 7 * 4);
            break;
        case MKTAG('s', 't', 'r', 'h'):
            /* stream header */
            stream_index++;
            tag1 = get_le32(pb);
            handler = get_le32(pb); /* codec tag */
#ifdef DEBUG
        print_tag("strh", tag1, -1);
#endif
            if(tag1 == MKTAG('i', 'a', 'v', 's') || tag1 == MKTAG('i', 'v', 'a', 's')){
                /*
                 * 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;
                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);
                ast->rate = get_le32(pb);
                stream_index = s->nb_streams - 1;
                url_fskip(pb, size - 7*4);
                break;
            }

            if (stream_index >= s->nb_streams) {
                url_fskip(pb, size - 8);
                break;
            }
            st = s->streams[stream_index];
            ast = st->priv_data;
            st->codec->stream_codec_tag= handler;

            get_le32(pb); /* flags */
            get_le16(pb); /* priority */
            get_le16(pb); /* language */
            get_le32(pb); /* initial frame */
            ast->scale = get_le32(pb);
            ast->rate = get_le32(pb);
            if(ast->scale && ast->rate){
            }else if(frame_period){
                ast->rate = 1000000;
                ast->scale = frame_period;
            }else{
                ast->rate = 25;
                ast->scale = 1;
            }
            av_set_pts_info(st, 64, ast->scale, ast->rate);

            ast->cum_len=get_le32(pb); /* start */
            nb_frames = get_le32(pb);

            st->start_time = 0;
            st->duration = nb_frames;
            get_le32(pb); /* buffer size */
            get_le32(pb); /* quality */
            ast->sample_size = get_le32(pb); /* sample ssize */
//            av_log(NULL, AV_LOG_DEBUG, "%d %d %d %d\n", ast->rate, ast->scale, ast->start, ast->sample_size);

            switch(tag1) {
            case MKTAG('v', 'i', 'd', 's'):
                codec_type = CODEC_TYPE_VIDEO;

                ast->sample_size = 0;
                break;
            case MKTAG('a', 'u', 'd', 's'):
                codec_type = CODEC_TYPE_AUDIO;
                break;
            case MKTAG('t', 'x', 't', 's'):
                //FIXME
                codec_type = CODEC_TYPE_DATA; //CODEC_TYPE_SUB ?  FIXME
                break;
            case MKTAG('p', 'a', 'd', 's'):
                codec_type = CODEC_TYPE_UNKNOWN;
                stream_index--;
                break;
            default:
                av_log(s, AV_LOG_ERROR, "unknown stream type %X\n", tag1);
                goto fail;
            }
            ast->frame_offset= ast->cum_len * FFMAX(ast->sample_size, 1);
            url_fskip(pb, size - 12 * 4);
            break;
        case MKTAG('s', 't', 'r', 'f'):
            /* stream header */
            if (stream_index >= s->nb_streams || avi->dv_demux) {
                url_fskip(pb, size);
            } else {
                st = s->streams[stream_index];
                switch(codec_type) {
                case CODEC_TYPE_VIDEO:
                    get_le32(pb); /* size */
                    st->codec->width = get_le32(pb);
                    st->codec->height = get_le32(pb);
                    get_le16(pb); /* panes */
                    st->codec->bits_per_sample= get_le16(pb); /* depth */
                    tag1 = get_le32(pb);
                    get_le32(pb); /* ImageSize */
                    get_le32(pb); /* XPelsPerMeter */
                    get_le32(pb); /* YPelsPerMeter */
                    get_le32(pb); /* ClrUsed */
                    get_le32(pb); /* ClrImportant */

                 if(size > 10*4 && size<(1<<30)){
                    st->codec->extradata_size= size - 10*4;
                    st->codec->extradata= av_malloc(st->codec->extradata_size + FF_INPUT_BUFFER_PADDING_SIZE);
                    get_buffer(pb, st->codec->extradata, st->codec->extradata_size);
                 }

                    if(st->codec->extradata_size & 1) //FIXME check if the encoder really did this correctly
                        get_byte(pb);

                    /* Extract palette from extradata if bpp <= 8 */
                    /* This code assumes that extradata contains only palette */
                    /* This is true for all paletted codecs implemented in ffmpeg */
                    if (st->codec->extradata_size && (st->codec->bits_per_sample <= 8)) {
                        st->codec->palctrl = av_mallocz(sizeof(AVPaletteControl));
#ifdef WORDS_BIGENDIAN
                        for (i = 0; i < FFMIN(st->codec->extradata_size, AVPALETTE_SIZE)/4; i++)
                            st->codec->palctrl->palette[i] = bswap_32(((uint32_t*)st->codec->extradata)[i]);
#else
                        memcpy(st->codec->palctrl->palette, st->codec->extradata,
                               FFMIN(st->codec->extradata_size, AVPALETTE_SIZE));
#endif
                        st->codec->palctrl->palette_changed = 1;
                    }

#ifdef DEBUG
                    print_tag("video", tag1, 0);
#endif
                    st->codec->codec_type = CODEC_TYPE_VIDEO;
                    st->codec->codec_tag = tag1;
                    st->codec->codec_id = codec_get_id(codec_bmp_tags, tag1);
                    if (st->codec->codec_id == CODEC_ID_XAN_WC4)
                        xan_video = 1;
                    st->need_parsing = 2; //only parse headers dont do slower repacketization, this is needed to get the pict type which is needed for generating correct pts
//                    url_fskip(pb, size - 5 * 4);
                    break;
                case CODEC_TYPE_AUDIO:
                    get_wav_header(pb, st->codec, size);
                    if(ast->sample_size && st->codec->block_align && ast->sample_size % st->codec->block_align)
                        av_log(s, AV_LOG_DEBUG, "invalid sample size or block align detected\n");
                    if (size%2) /* 2-aligned (fix for Stargate SG-1 - 3x18 - Shades of Grey.avi) */
                        url_fskip(pb, 1);
                    /* special case time: To support Xan DPCM, hardcode
                     * the format if Xxan is the video codec */
                    st->need_parsing = 1;
                    /* force parsing as several audio frames can be in
                       one packet */
                    if (xan_video)
                        st->codec->codec_id = CODEC_ID_XAN_DPCM;
                    break;
                default:
                    st->codec->codec_type = CODEC_TYPE_DATA;
                    st->codec->codec_id= CODEC_ID_NONE;
                    st->codec->codec_tag= 0;
                    url_fskip(pb, size);
                    break;
                }
            }
            break;
        case MKTAG('i', 'n', 'd', 'x'):
            i= url_ftell(pb);
            read_braindead_odml_indx(s, 0);
            avi->index_loaded=1;
            url_fseek(pb, i+size, SEEK_SET);
            break;
        default:
            /* skip tag */
            size += (size & 1);
            url_fskip(pb, size);
            break;
        }
    }
 end_of_header:
    /* check stream number */
    if (stream_index != s->nb_streams - 1) {
    fail:
        for(i=0;i<s->nb_streams;i++) {
            av_freep(&s->streams[i]->codec->extradata);
            av_freep(&s->streams[i]);
        }
        return -1;
    }

    if(!avi->index_loaded)
        avi_load_index(s);
    avi->index_loaded = 1;
    avi->non_interleaved |= guess_ni_flag(s);
    if(avi->non_interleaved)
        clean_index(s);

    return 0;
}

static int avi_read_packet(AVFormatContext *s, AVPacket *pkt)
{
    AVIContext *avi = s->priv_data;
    ByteIOContext *pb = &s->pb;
    int n, d[8], size;
    offset_t i, sync;
    void* dstr;