demux.c

alac decoder,内容详细

        {
            fprintf(stderr, "strange size for chunk inside stbl (%lu) (remaining: %lu)\n",
                    sub_chunk_len, size_remaining);
            return 0;
        }

        sub_chunk_id = stream_read_uint32(qtmovie->stream);

        switch (sub_chunk_id)
        {
        case MAKEFOURCC('s','t','s','d'):
            if (read_chunk_stsd(qtmovie, sub_chunk_len) == 0)
                return 0;
            break;
        case MAKEFOURCC('s','t','t','s'):
            read_chunk_stts(qtmovie, sub_chunk_len);
            break;
        case MAKEFOURCC('s','t','s','z'):
            read_chunk_stsz(qtmovie, sub_chunk_len);
            break;
        case MAKEFOURCC('s','t','s','c'):
        case MAKEFOURCC('s','t','c','o'):
            /* skip these, no indexing for us! */
            stream_skip(qtmovie->stream, sub_chunk_len - 8);
            break;
        default:
            fprintf(stderr, "(stbl) unknown chunk id: %c%c%c%c\n",
                    SPLITFOURCC(sub_chunk_id));
            return 0;
        }

        size_remaining -= sub_chunk_len;
    }

    return 1;
}

static int read_chunk_minf(qtmovie_t *qtmovie, size_t chunk_len)
{
    size_t dinf_size, stbl_size;
    size_t size_remaining = chunk_len - 8; /* FIXME WRONG */

  /**** SOUND HEADER CHUNK ****/
    if (stream_read_uint32(qtmovie->stream) != 16)
    {
        fprintf(stderr, "unexpected size in media info\n");
        return 0;
    }
    if (stream_read_uint32(qtmovie->stream) != MAKEFOURCC('s','m','h','d'))
    {
        fprintf(stderr, "not a sound header! can't handle this.\n");
        return 0;
    }
    /* now skip the rest */
    stream_skip(qtmovie->stream, 16 - 8);
    size_remaining -= 16;
  /****/

  /**** DINF CHUNK ****/
    dinf_size = stream_read_uint32(qtmovie->stream);
    if (stream_read_uint32(qtmovie->stream) != MAKEFOURCC('d','i','n','f'))
    {
        fprintf(stderr, "expected dinf, didn't get it.\n");
        return 0;
    }
    /* skip it */
    stream_skip(qtmovie->stream, dinf_size - 8);
    size_remaining -= dinf_size;
  /****/


  /**** SAMPLE TABLE ****/
    stbl_size = stream_read_uint32(qtmovie->stream);
    if (stream_read_uint32(qtmovie->stream) != MAKEFOURCC('s','t','b','l'))
    {
        fprintf(stderr, "expected stbl, didn't get it.\n");
        return 0;
    }
    if (read_chunk_stbl(qtmovie, stbl_size) == 0)
        return 0;
    size_remaining -= stbl_size;

    if (size_remaining)
    {
        fprintf(stderr, "oops\n");
        stream_skip(qtmovie->stream, size_remaining);
    }

    return 1;
}

static int read_chunk_mdia(qtmovie_t *qtmovie, size_t chunk_len)
{
    size_t size_remaining = chunk_len - 8; /* FIXME WRONG */

    while (size_remaining)
    {
        size_t sub_chunk_len;
        fourcc_t sub_chunk_id;

        sub_chunk_len = stream_read_uint32(qtmovie->stream);
        if (sub_chunk_len <= 1 || sub_chunk_len > size_remaining)
        {
            fprintf(stderr, "strange size for chunk inside mdia\n");
            return 0;
        }

        sub_chunk_id = stream_read_uint32(qtmovie->stream);

        switch (sub_chunk_id)
        {
        case MAKEFOURCC('m','d','h','d'):
            read_chunk_mdhd(qtmovie, sub_chunk_len);
            break;
        case MAKEFOURCC('h','d','l','r'):
            read_chunk_hdlr(qtmovie, sub_chunk_len);
            break;
        case MAKEFOURCC('m','i','n','f'):
            if (read_chunk_minf(qtmovie, sub_chunk_len) == 0)
                return 0;
            break;
        default:
            fprintf(stderr, "(mdia) unknown chunk id: %c%c%c%c\n",
                    SPLITFOURCC(sub_chunk_id));
            return 0;
        }

        size_remaining -= sub_chunk_len;
    }

    return 1;
}

/* 'trak' - a movie track - contains other atoms */
static int read_chunk_trak(qtmovie_t *qtmovie, size_t chunk_len)
{
    size_t size_remaining = chunk_len - 8; /* FIXME WRONG */

    while (size_remaining)
    {
        size_t sub_chunk_len;
        fourcc_t sub_chunk_id;

        sub_chunk_len = stream_read_uint32(qtmovie->stream);
        if (sub_chunk_len <= 1 || sub_chunk_len > size_remaining)
        {
            fprintf(stderr, "strange size for chunk inside trak\n");
            return 0;
        }

        sub_chunk_id = stream_read_uint32(qtmovie->stream);

        switch (sub_chunk_id)
        {
        case MAKEFOURCC('t','k','h','d'):
            read_chunk_tkhd(qtmovie, sub_chunk_len);
            break;
        case MAKEFOURCC('m','d','i','a'):
            if (read_chunk_mdia(qtmovie, sub_chunk_len) == 0)
                return 0;
            break;
        case MAKEFOURCC('e','d','t','s'):
            read_chunk_edts(qtmovie, sub_chunk_len);
            break;
        default:
            fprintf(stderr, "(trak) unknown chunk id: %c%c%c%c\n",
                    SPLITFOURCC(sub_chunk_id));
            return 0;
        }

        size_remaining -= sub_chunk_len;
    }

    return 1;
}

/* 'mvhd' movie header atom */
static void read_chunk_mvhd(qtmovie_t *qtmovie, size_t chunk_len)
{
    /* don't need anything from here atm, skip */
    size_t size_remaining = chunk_len - 8; /* FIXME WRONG */

    stream_skip(qtmovie->stream, size_remaining);
}

/* 'udta' user data.. contains tag info */
static void read_chunk_udta(qtmovie_t *qtmovie, size_t chunk_len)
{
    /* don't need anything from here atm, skip */
    size_t size_remaining = chunk_len - 8; /* FIXME WRONG */

    stream_skip(qtmovie->stream, size_remaining);
}

/* 'iods' */
static void read_chunk_iods(qtmovie_t *qtmovie, size_t chunk_len)
{
    /* don't need anything from here atm, skip */
    size_t size_remaining = chunk_len - 8; /* FIXME WRONG */

    stream_skip(qtmovie->stream, size_remaining);
}

/* 'moov' movie atom - contains other atoms */
static int read_chunk_moov(qtmovie_t *qtmovie, size_t chunk_len)
{
    size_t size_remaining = chunk_len - 8; /* FIXME WRONG */

    while (size_remaining)
    {
        size_t sub_chunk_len;
        fourcc_t sub_chunk_id;

        sub_chunk_len = stream_read_uint32(qtmovie->stream);
        if (sub_chunk_len <= 1 || sub_chunk_len > size_remaining)
        {
            fprintf(stderr, "strange size for chunk inside moov\n");
            return 0;
        }

        sub_chunk_id = stream_read_uint32(qtmovie->stream);

        switch (sub_chunk_id)
        {
        case MAKEFOURCC('m','v','h','d'):
            read_chunk_mvhd(qtmovie, sub_chunk_len);
            break;
        case MAKEFOURCC('t','r','a','k'):
            if (read_chunk_trak(qtmovie, sub_chunk_len) == 0)
                return 0;
            break;
        case MAKEFOURCC('u','d','t','a'):
            read_chunk_udta(qtmovie, sub_chunk_len);
            break;
        case MAKEFOURCC('e','l','s','t'):
            read_chunk_elst(qtmovie, sub_chunk_len);
            break;
        case MAKEFOURCC('i','o','d','s'):
            read_chunk_iods(qtmovie, sub_chunk_len);
            break;
        default:
            fprintf(stderr, "(moov) unknown chunk id: %c%c%c%c\n",
                    SPLITFOURCC(sub_chunk_id));
            return 0;
        }

        size_remaining -= sub_chunk_len;
    }

    return 1;
}

static void read_chunk_mdat(qtmovie_t *qtmovie, size_t chunk_len, int skip_mdat)
{
    size_t size_remaining = chunk_len - 8; /* FIXME WRONG */

    if (size_remaining == 0) return;

    qtmovie->res->mdat_len = (uint32_t)size_remaining;
    if (skip_mdat)
    {
        qtmovie->saved_mdat_pos = stream_tell(qtmovie->stream);
        stream_skip(qtmovie->stream, size_remaining);
    }
#if 0
    qtmovie->res->mdat = malloc(size_remaining);

    stream_read(qtmovie->stream, size_remaining, qtmovie->res->mdat);
#endif
}

static int set_saved_mdat(qtmovie_t *qtmovie)
{
    if (qtmovie->saved_mdat_pos == -1)
    {
        fprintf(stderr, "stream contains mdat before moov but is not seekable\n");
        return 0;
    }

    if (stream_setpos(qtmovie->stream, qtmovie->saved_mdat_pos))
    {
        fprintf(stderr, "error while seeking stream to mdat pos\n");
        return 0;
    }

    return 1;
}

int qtmovie_read(stream_t *file, demux_res_t *demux_res)
{
    int found_moov = 0;
    int found_mdat = 0;
    qtmovie_t *qtmovie;

    qtmovie = (qtmovie_t*)malloc(sizeof(qtmovie_t));

    /* construct the stream */
    qtmovie->stream = file;

    qtmovie->res = demux_res;

    memset(demux_res, 0, sizeof(demux_res_t));

    /* read the chunks */
    while (1)
    {
        size_t chunk_len;
        fourcc_t chunk_id;

        chunk_len = stream_read_uint32(qtmovie->stream);
        if (stream_eof(qtmovie->stream))
        {
            return 0;
        }

        if (chunk_len == 1)
        {
            fprintf(stderr, "need 64bit support\n");
            return 0;
        }
        chunk_id = stream_read_uint32(qtmovie->stream);

        switch (chunk_id)
        {
        case MAKEFOURCC('f','t','y','p'):
            read_chunk_ftyp(qtmovie, chunk_len);
            break;
        case MAKEFOURCC('m','o','o','v'):
            if (read_chunk_moov(qtmovie, chunk_len) == 0)
                return 0; /* failed to read moov, can't do anything */
            if (found_mdat)
            {
                return set_saved_mdat(qtmovie);
            }
            found_moov = 1;
            break;
            /* if we hit mdat before we've found moov, record the position
             * and move on. We can then come back to mdat later.
             * This presumes the stream supports seeking backwards.
             */
        case MAKEFOURCC('m','d','a','t'):
            read_chunk_mdat(qtmovie, chunk_len, !found_moov);
            if (found_moov)
                return 1;
            found_mdat = 1;
            break;

            /*  these following atoms can be skipped !!!! */
        case MAKEFOURCC('f','r','e','e'):
            stream_skip(qtmovie->stream, chunk_len - 8); /* FIXME not 8 */
            break;
        default:
            fprintf(stderr, "(top) unknown chunk id: %c%c%c%c\n",
                    SPLITFOURCC(chunk_id));
            return 0;
        }

    }
    return 0;
}