mov.c

ffmpeg源码分析

            code >>= 5;
        }
        return 1;
    }
    /* old fashion apple lang code */
    if (code >= (sizeof(mov_mdhd_language_map)/sizeof(char *)))
        return 0;
    if (!mov_mdhd_language_map[code])
        return 0;
    strncpy(to, mov_mdhd_language_map[code], 4);
    return 1;
}

extern int ff_mov_iso639_to_lang(const char *lang, int mp4); /* for movenc.c */
int ff_mov_iso639_to_lang(const char *lang, int mp4)
{
    int i, code = 0;

    /* old way, only for QT? */
    for (i = 0; !mp4 && (i < (sizeof(mov_mdhd_language_map)/sizeof(char *))); i++) {
        if (mov_mdhd_language_map[i] && !strcmp(lang, mov_mdhd_language_map[i]))
            return i;
    }
    /* XXX:can we do that in mov too? */
    if (!mp4)
        return 0;
    /* handle undefined as such */
    if (lang[0] == '\0')
        lang = "und";
    /* 5bit ascii */
    for (i = 0; i < 3; i++) {
        unsigned char c = (unsigned char)lang[i];
        if (c < 0x60)
            return 0;
        if (c > 0x60 + 0x1f)
            return 0;
        code <<= 5;
        code |= (c - 0x60);
    }
    return code;
}

static int mov_read_leaf(MOVContext *c, ByteIOContext *pb, MOV_atom_t atom)
{
    if (atom.size>1)
        url_fskip(pb, atom.size);
/*        url_seek(pb, atom_offset+atom.size, SEEK_SET); */
    return 0;
}

static int mov_read_default(MOVContext *c, ByteIOContext *pb, MOV_atom_t atom)
{
    int64_t total_size = 0;
    MOV_atom_t a;
    int i;
    int err = 0;

    a.offset = atom.offset;

    if (atom.size < 0)
        atom.size = 0x7fffffffffffffffLL;
    while(((total_size + 8) < atom.size) && !url_feof(pb) && !err) {
        a.size = atom.size;
        a.type=0L;
        if(atom.size >= 8) {
            a.size = get_be32(pb);
            a.type = get_le32(pb);
        }
        total_size += 8;
        a.offset += 8;
        dprintf("type: %08x  %.4s  sz: %"PRIx64"  %"PRIx64"   %"PRIx64"\n", a.type, (char*)&a.type, a.size, atom.size, total_size);
        if (a.size == 1) { /* 64 bit extended size */
            a.size = get_be64(pb) - 8;
            a.offset += 8;
            total_size += 8;
        }
        if (a.size == 0) {
            a.size = atom.size - total_size;
            if (a.size <= 8)
                break;
        }
        for (i = 0; c->parse_table[i].type != 0L
             && c->parse_table[i].type != a.type; i++)
            /* empty */;

        a.size -= 8;

        if(a.size < 0)
            break;

        if (c->parse_table[i].type == 0) { /* skip leaf atoms data */
            url_fskip(pb, a.size);
        } else {
            err = (c->parse_table[i].func)(c, pb, a);
        }

        a.offset += a.size;
        total_size += a.size;
    }

    if (!err && total_size < atom.size && atom.size < 0x7ffff) {
        url_fskip(pb, atom.size - total_size);
    }

    return err;
}

static int mov_read_ctab(MOVContext *c, ByteIOContext *pb, MOV_atom_t atom)
{
#if 1
    url_fskip(pb, atom.size); // for now
#else
    VERY VERY BROKEN, NEVER execute this, needs rewrite
    unsigned int len;
    MOV_ctab_t *t;
    c->ctab = av_realloc(c->ctab, ++c->ctab_size);
    t = c->ctab[c->ctab_size];
    t->seed = get_be32(pb);
    t->flags = get_be16(pb);
    t->size = get_be16(pb) + 1;
    len = 2 * t->size * 4;
    if (len > 0) {
        t->clrs = av_malloc(len); // 16bit A R G B
        if (t->clrs)
            get_buffer(pb, t->clrs, len);
    }
#endif

    return 0;
}

static int mov_read_hdlr(MOVContext *c, ByteIOContext *pb, MOV_atom_t atom)
{
    AVStream *st = c->fc->streams[c->fc->nb_streams-1];
    int len = 0;
    uint32_t type;
    uint32_t ctype;

    get_byte(pb); /* version */
    get_byte(pb); get_byte(pb); get_byte(pb); /* flags */

    /* component type */
    ctype = get_le32(pb);
    type = get_le32(pb); /* component subtype */

    dprintf("ctype= %c%c%c%c (0x%08lx)\n", *((char *)&ctype), ((char *)&ctype)[1], ((char *)&ctype)[2], ((char *)&ctype)[3], (long) ctype);
    dprintf("stype= %c%c%c%c\n", *((char *)&type), ((char *)&type)[1], ((char *)&type)[2], ((char *)&type)[3]);
    if(ctype == MKTAG('m', 'h', 'l', 'r')) /* MOV */
        c->mp4 = 0;
    else if(ctype == 0)
        c->mp4 = 1;
    if(type == MKTAG('v', 'i', 'd', 'e'))
        st->codec->codec_type = CODEC_TYPE_VIDEO;
    else if(type == MKTAG('s', 'o', 'u', 'n'))
        st->codec->codec_type = CODEC_TYPE_AUDIO;
    get_be32(pb); /* component  manufacture */
    get_be32(pb); /* component flags */
    get_be32(pb); /* component flags mask */

    if(atom.size <= 24)
        return 0; /* nothing left to read */
    /* XXX: MP4 uses a C string, not a pascal one */
    /* component name */

    if(c->mp4) {
        /* .mp4: C string */
        while(get_byte(pb) && (++len < (atom.size - 24)));
    } else {
        /* .mov: PASCAL string */
        len = get_byte(pb);
        url_fskip(pb, len);
    }

    url_fskip(pb, atom.size - (url_ftell(pb) - atom.offset));
    return 0;
}

static int mov_mp4_read_descr_len(ByteIOContext *pb)
{
    int len = 0;
    int count = 4;
    while (count--) {
        int c = get_byte(pb);
        len = (len << 7) | (c & 0x7f);
        if (!(c & 0x80))
            break;
    }
    return len;
}

static int mov_mp4_read_descr(ByteIOContext *pb, int *tag)
{
    int len;
    *tag = get_byte(pb);
    len = mov_mp4_read_descr_len(pb);
    dprintf("MPEG4 description: tag=0x%02x len=%d\n", *tag, len);
    return len;
}

static int mov_read_esds(MOVContext *c, ByteIOContext *pb, MOV_atom_t atom)
{
    AVStream *st = c->fc->streams[c->fc->nb_streams-1];
    MOVStreamContext *sc = (MOVStreamContext *)st->priv_data;
    int64_t start_pos = url_ftell(pb);
    int tag, len;

    /* Well, broken but suffisant for some MP4 streams */
    get_be32(pb); /* version + flags */
    len = mov_mp4_read_descr(pb, &tag);
    if (tag == MP4ESDescrTag) {
        get_be16(pb); /* ID */
        get_byte(pb); /* priority */
    } else
        get_be16(pb); /* ID */

    len = mov_mp4_read_descr(pb, &tag);
    if (tag == MP4DecConfigDescrTag) {
        sc->esds.object_type_id = get_byte(pb);
        sc->esds.stream_type = get_byte(pb);
        sc->esds.buffer_size_db = get_be24(pb);
        sc->esds.max_bitrate = get_be32(pb);
        sc->esds.avg_bitrate = get_be32(pb);

        st->codec->codec_id= codec_get_id(ff_mov_obj_type, sc->esds.object_type_id);
        len = mov_mp4_read_descr(pb, &tag);
        if (tag == MP4DecSpecificDescrTag) {
            dprintf("Specific MPEG4 header len=%d\n", len);
            st->codec->extradata = (uint8_t*) av_mallocz(len + FF_INPUT_BUFFER_PADDING_SIZE);
            if (st->codec->extradata) {
                get_buffer(pb, st->codec->extradata, len);
                st->codec->extradata_size = len;
                /* from mplayer */
                if ((*(uint8_t *)st->codec->extradata >> 3) == 29) {
                    st->codec->codec_id = CODEC_ID_MP3ON4;
                }
            }
        }
    }
    /* in any case, skip garbage */
    url_fskip(pb, atom.size - ((url_ftell(pb) - start_pos)));
    return 0;
}

/* this atom contains actual media data */
static int mov_read_mdat(MOVContext *c, ByteIOContext *pb, MOV_atom_t atom)
{
    if(atom.size == 0) /* wrong one (MP4) */
        return 0;
    c->found_mdat=1;
    c->mdat_offset = atom.offset;
    c->mdat_size = atom.size;
    if(c->found_moov)
        return 1; /* found both, just go */
    url_fskip(pb, atom.size);
    return 0; /* now go for moov */
}

static int mov_read_ftyp(MOVContext *c, ByteIOContext *pb, MOV_atom_t atom)
{
    uint32_t type = get_le32(pb);

    /* from mplayer */
    switch (type) {
    case MKTAG('i', 's', 'o', 'm'):
    case MKTAG('m', 'p', '4', '1'):
    case MKTAG('m', 'p', '4', '2'):
    case MKTAG('3', 'g', 'p', '1'):
    case MKTAG('3', 'g', 'p', '2'):
    case MKTAG('3', 'g', '2', 'a'):
    case MKTAG('3', 'g', 'p', '3'):
    case MKTAG('3', 'g', 'p', '4'):
    case MKTAG('3', 'g', 'p', '5'):
    case MKTAG('m', 'm', 'p', '4'): /* Mobile MP4 */
    case MKTAG('M', '4', 'A', ' '): /* Apple iTunes AAC-LC Audio */
    case MKTAG('M', '4', 'P', ' '): /* Apple iTunes AAC-LC Protected Audio */
    case MKTAG('m', 'j', 'p', '2'): /* Motion Jpeg 2000 */
        c->mp4 = 1;
    case MKTAG('q', 't', ' ', ' '):
    default:
        av_log(c->fc, AV_LOG_DEBUG, "ISO: File Type Major Brand: %.4s\n",(char *)&type);
    }
    get_be32(pb); /* minor version */
    url_fskip(pb, atom.size - 8);
    return 0;
}

/* this atom should contain all header atoms */
static int mov_read_moov(MOVContext *c, ByteIOContext *pb, MOV_atom_t atom)
{
    int err;

    err = mov_read_default(c, pb, atom);
    /* we parsed the 'moov' atom, we can terminate the parsing as soon as we find the 'mdat' */
    /* so we don't parse the whole file if over a network */
    c->found_moov=1;
    if(c->found_mdat)
        return 1; /* found both, just go */
    return 0; /* now go for mdat */
}


static int mov_read_mdhd(MOVContext *c, ByteIOContext *pb, MOV_atom_t atom)
{
    AVStream *st = c->fc->streams[c->fc->nb_streams-1];
    MOVStreamContext *sc = (MOVStreamContext *)st->priv_data;
    int version = get_byte(pb);
    int lang;

    if (version > 1)
        return 1; /* unsupported */

    get_byte(pb); get_byte(pb);
    get_byte(pb); /* flags */

    if (version == 1) {
        get_be64(pb);
        get_be64(pb);
    } else {
        get_be32(pb); /* creation time */
        get_be32(pb); /* modification time */
    }

    sc->time_scale = get_be32(pb);
    st->duration = (version == 1) ? get_be64(pb) : get_be32(pb); /* duration */

    lang = get_be16(pb); /* language */
    ff_mov_lang_to_iso639(lang, st->language);
    get_be16(pb); /* quality */

    return 0;
}

static int mov_read_mvhd(MOVContext *c, ByteIOContext *pb, MOV_atom_t atom)
{
    int version = get_byte(pb); /* version */
    get_byte(pb); get_byte(pb); get_byte(pb); /* flags */

    if (version == 1) {
        get_be64(pb);
        get_be64(pb);
    } else {
        get_be32(pb); /* creation time */
        get_be32(pb); /* modification time */
    }
    c->time_scale = get_be32(pb); /* time scale */
#ifdef DEBUG
    av_log(NULL, AV_LOG_DEBUG, "time scale = %i\n", c->time_scale);
#endif
    c->duration = (version == 1) ? get_be64(pb) : get_be32(pb); /* duration */
    get_be32(pb); /* preferred scale */

    get_be16(pb); /* preferred volume */

    url_fskip(pb, 10); /* reserved */

    url_fskip(pb, 36); /* display matrix */

    get_be32(pb); /* preview time */
    get_be32(pb); /* preview duration */
    get_be32(pb); /* poster time */
    get_be32(pb); /* selection time */
    get_be32(pb); /* selection duration */
    get_be32(pb); /* current time */
    get_be32(pb); /* next track ID */

    return 0;
}

static int mov_read_smi(MOVContext *c, ByteIOContext *pb, MOV_atom_t atom)
{
    AVStream *st = c->fc->streams[c->fc->nb_streams-1];