mpeg4video.c

uclinux 下的vlc播放器源代码

            /* When starting the stream we can have the first frame with
             * a null DTS (i_interpolated_pts is initialized to 0) */
            if( !p_pic->i_dts ) p_pic->i_dts = p_pic->i_pts;

            /* So p_block doesn't get re-added several times */
            *pp_block = block_BytestreamPop( &p_sys->bytestream );

            p_sys->i_state = STATE_NOSYNC;

            return p_pic;
        }
    }
}

/*****************************************************************************
 * ParseMPEGBlock: Re-assemble fragments into a block containing a picture
 *****************************************************************************/
static block_t *ParseMPEGBlock( decoder_t *p_dec, block_t *p_frag )
{
    decoder_sys_t *p_sys = p_dec->p_sys;
    block_t *p_pic = NULL;

    if( p_frag->p_buffer[3] == 0xB0 || p_frag->p_buffer[3] == 0xB1 )
    {
#if 0
        /* Remove VOS start/end code from the original stream */
        block_Release( p_frag );
#else
        /* Append the block for now since ts/ps muxers rely on VOL
         * being present in the stream */
        block_ChainLastAppend( &p_sys->pp_last, p_frag );
#endif
        return NULL;
    }
    if( p_frag->p_buffer[3] >= 0x20 && p_frag->p_buffer[3] <= 0x2f )
    {
        /* Copy the complete VOL */
        if( p_dec->fmt_out.i_extra != p_frag->i_buffer )
        {
            p_dec->fmt_out.p_extra =
                realloc( p_dec->fmt_out.p_extra, p_frag->i_buffer );
            p_dec->fmt_out.i_extra = p_frag->i_buffer;
        }
        memcpy( p_dec->fmt_out.p_extra, p_frag->p_buffer, p_frag->i_buffer );
        ParseVOL( p_dec, &p_dec->fmt_out,
                  p_dec->fmt_out.p_extra, p_dec->fmt_out.i_extra );

#if 0
        /* Remove from the original stream */
        block_Release( p_frag );
#else
        /* Append the block for now since ts/ps muxers rely on VOL
         * being present in the stream */
        block_ChainLastAppend( &p_sys->pp_last, p_frag );
#endif
        return NULL;
    }
    else
    {
        if( !p_dec->fmt_out.i_extra )
        {
            msg_Warn( p_dec, "waiting for VOL" );
            block_Release( p_frag );
            return NULL;
        }

        /* Append the block */
        block_ChainLastAppend( &p_sys->pp_last, p_frag );
    }

    if( p_frag->p_buffer[3] == 0xb6 &&
        ParseVOP( p_dec, p_frag ) == VLC_SUCCESS )
    {
        /* We are dealing with a VOP */
        p_pic = block_ChainGather( p_sys->p_frame );
        p_pic->i_pts = p_sys->i_interpolated_pts;
        p_pic->i_dts = p_sys->i_interpolated_dts;

        /* Reset context */
        p_sys->p_frame = NULL;
        p_sys->pp_last = &p_sys->p_frame;
    }

    return p_pic;
}

/* ParseVOL:
 *  TODO:
 *      - support aspect ratio
 */
static int ParseVOL( decoder_t *p_dec, es_format_t *fmt,
                     uint8_t *p_vol, int i_vol )
{
    decoder_sys_t *p_sys = p_dec->p_sys;
    int i_vo_type, i_vo_ver_id, i_ar, i_shape;
    bs_t s;

    for( ;; )
    {
        if( p_vol[0] == 0x00 && p_vol[1] == 0x00 && p_vol[2] == 0x01 &&
            p_vol[3] >= 0x20 && p_vol[3] <= 0x2f ) break;

        p_vol++; i_vol--;
        if( i_vol <= 4 ) return VLC_EGENERIC;
    }

    bs_init( &s, &p_vol[4], i_vol - 4 );

    bs_skip( &s, 1 );   /* random access */
    i_vo_type = bs_read( &s, 8 );
    if( bs_read1( &s ) )
    {
        i_vo_ver_id = bs_read( &s, 4 );
        bs_skip( &s, 3 );
    }
    else
    {
        i_vo_ver_id = 1;
    }
    i_ar = bs_read( &s, 4 );
    if( i_ar == 0xf )
    {
        int i_ar_width, i_ar_height;

        i_ar_width = bs_read( &s, 8 );
        i_ar_height= bs_read( &s, 8 );
    }
    if( bs_read1( &s ) )
    {
        int i_chroma_format;
        int i_low_delay;

        /* vol control parameter */
        i_chroma_format = bs_read( &s, 2 );
        i_low_delay = bs_read1( &s );

        if( bs_read1( &s ) )
        {
            bs_skip( &s, 16 );
            bs_skip( &s, 16 );
            bs_skip( &s, 16 );
            bs_skip( &s, 3 );
            bs_skip( &s, 11 );
            bs_skip( &s, 1 );
            bs_skip( &s, 16 );
        }
    }
    /* shape 0->RECT, 1->BIN, 2->BIN_ONLY, 3->GRAY */
    i_shape = bs_read( &s, 2 );
    if( i_shape == 3 && i_vo_ver_id != 1 )
    {
        bs_skip( &s, 4 );
    }

    if( !bs_read1( &s ) ) return VLC_EGENERIC; /* Marker */

    p_sys->i_fps_num = bs_read( &s, 16 ); /* Time increment resolution*/
    if( !p_sys->i_fps_num ) p_sys->i_fps_num = 1;

    if( !bs_read1( &s ) ) return VLC_EGENERIC; /* Marker */

    if( bs_read1( &s ) )
    {
        int i_time_increment_bits = vlc_log2( p_sys->i_fps_num - 1 ) + 1;

        if( i_time_increment_bits < 1 ) i_time_increment_bits = 1;

        p_sys->i_fps_den = bs_read( &s, i_time_increment_bits );
    }
    if( i_shape == 0 )
    {
        bs_skip( &s, 1 );
        fmt->video.i_width = bs_read( &s, 13 );
        bs_skip( &s, 1 );
        fmt->video.i_height= bs_read( &s, 13 );
        bs_skip( &s, 1 );
    }

    return VLC_SUCCESS;
}

static int ParseVOP( decoder_t *p_dec, block_t *p_vop )
{
    decoder_sys_t *p_sys = p_dec->p_sys;
    int64_t i_time_increment, i_time_ref;
    int i_modulo_time_base = 0, i_time_increment_bits;
    bs_t s;

    bs_init( &s, &p_vop->p_buffer[4], p_vop->i_buffer - 4 );

    switch( bs_read( &s, 2 ) )
    {
    case 0:
        p_sys->i_flags = BLOCK_FLAG_TYPE_I;
        break;
    case 1:
        p_sys->i_flags = BLOCK_FLAG_TYPE_P;
        break;
    case 2:
        p_sys->i_flags = BLOCK_FLAG_TYPE_B;
        p_sys->b_frame = VLC_TRUE;
        break;
    case 3: /* gni ? */
        p_sys->i_flags = BLOCK_FLAG_TYPE_PB;
        break;
    }

    while( bs_read( &s, 1 ) ) i_modulo_time_base++;
    if( !bs_read1( &s ) ) return VLC_EGENERIC; /* Marker */

    /* VOP time increment */
    i_time_increment_bits = vlc_log2(p_dec->p_sys->i_fps_num - 1) + 1;
    if( i_time_increment_bits < 1 ) i_time_increment_bits = 1;
    i_time_increment = bs_read( &s, i_time_increment_bits );

    /* Interpolate PTS/DTS */
    if( !(p_sys->i_flags & BLOCK_FLAG_TYPE_B) )
    {
        p_sys->i_last_time_ref = p_sys->i_time_ref;
        p_sys->i_time_ref +=
            (i_modulo_time_base * p_dec->p_sys->i_fps_num);
        i_time_ref = p_sys->i_time_ref;
    }
    else
    {
        i_time_ref = p_sys->i_last_time_ref +
            (i_modulo_time_base * p_dec->p_sys->i_fps_num);
    }

#if 0
    msg_Err( p_dec, "interp pts/dts (%lli,%lli), pts/dts (%lli,%lli)",
             p_sys->i_interpolated_pts, p_sys->i_interpolated_dts,
             p_vop->i_pts, p_vop->i_dts );
#endif

    if( p_dec->p_sys->i_fps_num < 5 && /* Work-around buggy streams */
        p_dec->fmt_in.video.i_frame_rate > 0 &&
        p_dec->fmt_in.video.i_frame_rate_base > 0 )
    {
        p_sys->i_interpolated_pts += I64C(1000000) *
        p_dec->fmt_in.video.i_frame_rate_base *
        p_vop->i_rate / INPUT_RATE_DEFAULT /
        p_dec->fmt_in.video.i_frame_rate;
    }
    else if( p_dec->p_sys->i_fps_num )
        p_sys->i_interpolated_pts +=
            ( I64C(1000000) * (i_time_ref + i_time_increment -
              p_sys->i_last_time - p_sys->i_last_timeincr) *
              p_vop->i_rate / INPUT_RATE_DEFAULT /
              p_dec->p_sys->i_fps_num );

    p_sys->i_last_time = i_time_ref;
    p_sys->i_last_timeincr = i_time_increment;

    /* Correct interpolated dts when we receive a new pts/dts */
    if( p_vop->i_pts > 0 )
        p_sys->i_interpolated_pts = p_vop->i_pts;
    if( p_vop->i_dts > 0 )
        p_sys->i_interpolated_dts = p_vop->i_dts;

    if( (p_sys->i_flags & BLOCK_FLAG_TYPE_B) || !p_sys->b_frame )
    {
        /* Trivial case (DTS == PTS) */

        p_sys->i_interpolated_dts = p_sys->i_interpolated_pts;

        if( p_vop->i_pts > 0 )
            p_sys->i_interpolated_dts = p_vop->i_pts;
        if( p_vop->i_dts > 0 )
            p_sys->i_interpolated_dts = p_vop->i_dts;

        p_sys->i_interpolated_pts = p_sys->i_interpolated_dts;
    }
    else
    {
        if( p_sys->i_last_ref_pts > 0 )
            p_sys->i_interpolated_dts = p_sys->i_last_ref_pts;

        p_sys->i_last_ref_pts = p_sys->i_interpolated_pts;
    }

    return VLC_SUCCESS;
}

/* look at ffmpeg av_log2 ;) */
static int vlc_log2( unsigned int v )
{
    int n = 0;
    static const int vlc_log2_table[16] =
    {
        0,0,1,1,2,2,2,2, 3,3,3,3,3,3,3,3
    };

    if( v&0xffff0000 )
    {
        v >>= 16;
        n += 16;
    }
    if( v&0xff00 )
    {
        v >>= 8;
        n += 8;
    }
    if( v&0xf0 )
    {
        v >>= 4;
        n += 4;
    }
    n += vlc_log2_table[v];

    return n;
}