header.c

MPEG2的编码的加密和解码的C源程序

    int i;

    for (i = 0; i < 3; i++)
	if (mpeg2dec->fbuf[1] != &mpeg2dec->fbuf_alloc[i].fbuf &&
	    mpeg2dec->fbuf[2] != &mpeg2dec->fbuf_alloc[i].fbuf) {
	    mpeg2dec->fbuf[0] = &mpeg2dec->fbuf_alloc[i].fbuf;
	    mpeg2dec->info.current_fbuf = mpeg2dec->fbuf[0];
	    if (b_type || (mpeg2dec->sequence.flags & SEQ_FLAG_LOW_DELAY)) {
		if (b_type || mpeg2dec->convert)
		    mpeg2dec->info.discard_fbuf = mpeg2dec->fbuf[0];
		mpeg2dec->info.display_fbuf = mpeg2dec->fbuf[0];
	    }
	    break;
	}
}

mpeg2_state_t mpeg2_header_picture_start (mpeg2dec_t * mpeg2dec)
{
    mpeg2_picture_t * picture = &(mpeg2dec->new_picture);

    mpeg2dec->state = ((mpeg2dec->state != STATE_SLICE_1ST) ?
		       STATE_PICTURE : STATE_PICTURE_2ND);
    picture->flags = 0;
    picture->tag = picture->tag2 = 0;
    if (mpeg2dec->num_tags) {
	if (mpeg2dec->bytes_since_tag >= 4) {
	    mpeg2dec->num_tags = 0;
	    picture->tag = mpeg2dec->tag_current;
	    picture->tag2 = mpeg2dec->tag2_current;
	    picture->flags = PIC_FLAG_TAGS;
	} else if (mpeg2dec->num_tags > 1) {
	    mpeg2dec->num_tags = 1;
	    picture->tag = mpeg2dec->tag_previous;
	    picture->tag2 = mpeg2dec->tag2_previous;
	    picture->flags = PIC_FLAG_TAGS;
	}
    }
    picture->display_offset[0].x = picture->display_offset[1].x =
	picture->display_offset[2].x = mpeg2dec->display_offset_x;
    picture->display_offset[0].y = picture->display_offset[1].y =
	picture->display_offset[2].y = mpeg2dec->display_offset_y;
    return mpeg2_parse_header (mpeg2dec);
}

int mpeg2_header_picture (mpeg2dec_t * mpeg2dec)
{
    uint8_t * buffer = mpeg2dec->chunk_start;
    mpeg2_picture_t * picture = &(mpeg2dec->new_picture);
    mpeg2_decoder_t * decoder = &(mpeg2dec->decoder);
    int type;

    type = (buffer [1] >> 3) & 7;
    mpeg2dec->ext_state = PIC_CODING_EXT;

    picture->temporal_reference = (buffer[0] << 2) | (buffer[1] >> 6);

    picture->flags |= type;

    if (type == PIC_FLAG_CODING_TYPE_P || type == PIC_FLAG_CODING_TYPE_B) {
	/* forward_f_code and backward_f_code - used in mpeg1 only */
	decoder->f_motion.f_code[1] = (buffer[3] >> 2) & 1;
	decoder->f_motion.f_code[0] =
	    (((buffer[3] << 1) | (buffer[4] >> 7)) & 7) - 1;
	decoder->b_motion.f_code[1] = (buffer[4] >> 6) & 1;
	decoder->b_motion.f_code[0] = ((buffer[4] >> 3) & 7) - 1;
    }

    /* XXXXXX decode extra_information_picture as well */

    picture->nb_fields = 2;

    mpeg2dec->q_scale_type = 0;
    decoder->intra_dc_precision = 7;
    decoder->frame_pred_frame_dct = 1;
    decoder->concealment_motion_vectors = 0;
    decoder->scan = mpeg2_scan_norm;
    decoder->picture_structure = FRAME_PICTURE;
    mpeg2dec->copy_matrix = 0;

    return 0;
}

static int picture_coding_ext (mpeg2dec_t * mpeg2dec)
{
    uint8_t * buffer = mpeg2dec->chunk_start;
    mpeg2_picture_t * picture = &(mpeg2dec->new_picture);
    mpeg2_decoder_t * decoder = &(mpeg2dec->decoder);
    uint32_t flags;

    /* pre subtract 1 for use later in compute_motion_vector */
    decoder->f_motion.f_code[0] = (buffer[0] & 15) - 1;
    decoder->f_motion.f_code[1] = (buffer[1] >> 4) - 1;
    decoder->b_motion.f_code[0] = (buffer[1] & 15) - 1;
    decoder->b_motion.f_code[1] = (buffer[2] >> 4) - 1;

    flags = picture->flags;
    decoder->intra_dc_precision = 7 - ((buffer[2] >> 2) & 3);
    decoder->picture_structure = buffer[2] & 3;
    switch (decoder->picture_structure) {
    case TOP_FIELD:
	flags |= PIC_FLAG_TOP_FIELD_FIRST;
    case BOTTOM_FIELD:
	picture->nb_fields = 1;
	break;
    case FRAME_PICTURE:
	if (!(mpeg2dec->sequence.flags & SEQ_FLAG_PROGRESSIVE_SEQUENCE)) {
	    picture->nb_fields = (buffer[3] & 2) ? 3 : 2;
	    flags |= (buffer[3] & 128) ? PIC_FLAG_TOP_FIELD_FIRST : 0;
	} else
	    picture->nb_fields = (buffer[3]&2) ? ((buffer[3]&128) ? 6 : 4) : 2;
	break;
    default:
	return 1;
    }
    decoder->top_field_first = buffer[3] >> 7;
    decoder->frame_pred_frame_dct = (buffer[3] >> 6) & 1;
    decoder->concealment_motion_vectors = (buffer[3] >> 5) & 1;
    mpeg2dec->q_scale_type = buffer[3] & 16;
    decoder->intra_vlc_format = (buffer[3] >> 3) & 1;
    decoder->scan = (buffer[3] & 4) ? mpeg2_scan_alt : mpeg2_scan_norm;
    flags |= (buffer[4] & 0x80) ? PIC_FLAG_PROGRESSIVE_FRAME : 0;
    if (buffer[4] & 0x40)
	flags |= (((buffer[4]<<26) | (buffer[5]<<18) | (buffer[6]<<10)) &
		  PIC_MASK_COMPOSITE_DISPLAY) | PIC_FLAG_COMPOSITE_DISPLAY;
    picture->flags = flags;

    mpeg2dec->ext_state = PIC_DISPLAY_EXT | COPYRIGHT_EXT | QUANT_MATRIX_EXT;

    return 0;
}

static int picture_display_ext (mpeg2dec_t * mpeg2dec)
{
    uint8_t * buffer = mpeg2dec->chunk_start;
    mpeg2_picture_t * picture = &(mpeg2dec->new_picture);
    int i, nb_pos;

    nb_pos = picture->nb_fields;
    if (mpeg2dec->sequence.flags & SEQ_FLAG_PROGRESSIVE_SEQUENCE)
	nb_pos >>= 1;

    for (i = 0; i < nb_pos; i++) {
	int x, y;

	x = ((buffer[4*i] << 24) | (buffer[4*i+1] << 16) |
	     (buffer[4*i+2] << 8) | buffer[4*i+3]) >> (11-2*i);
	y = ((buffer[4*i+2] << 24) | (buffer[4*i+3] << 16) |
	     (buffer[4*i+4] << 8) | buffer[4*i+5]) >> (10-2*i);
	if (! (x & y & 1))
	    return 1;
	picture->display_offset[i].x = mpeg2dec->display_offset_x = x >> 1;
	picture->display_offset[i].y = mpeg2dec->display_offset_y = y >> 1;
    }
    for (; i < 3; i++) {
	picture->display_offset[i].x = mpeg2dec->display_offset_x;
	picture->display_offset[i].y = mpeg2dec->display_offset_y;
    }
    return 0;
}

void mpeg2_header_picture_finalize (mpeg2dec_t * mpeg2dec, uint32_t accels)
{
    mpeg2_decoder_t * decoder = &(mpeg2dec->decoder);
    int old_type_b = (decoder->coding_type == B_TYPE);
    int low_delay = mpeg2dec->sequence.flags & SEQ_FLAG_LOW_DELAY;

    finalize_matrix (mpeg2dec);
    decoder->coding_type = mpeg2dec->new_picture.flags & PIC_MASK_CODING_TYPE;

    if (mpeg2dec->state == STATE_PICTURE) {
	mpeg2_picture_t * picture;
	mpeg2_picture_t * other;

	decoder->second_field = 0;

	picture = other = mpeg2dec->pictures;
	if (old_type_b ^ (mpeg2dec->picture < mpeg2dec->pictures + 2))
	    picture += 2;
	else
	    other += 2;
	mpeg2dec->picture = picture;
	*picture = mpeg2dec->new_picture;

	if (!old_type_b) {
	    mpeg2dec->fbuf[2] = mpeg2dec->fbuf[1];
	    mpeg2dec->fbuf[1] = mpeg2dec->fbuf[0];
	}
	mpeg2dec->fbuf[0] = NULL;
	mpeg2_reset_info (&(mpeg2dec->info));
	mpeg2dec->info.current_picture = picture;
	mpeg2dec->info.display_picture = picture;
	if (decoder->coding_type != B_TYPE) {
	    if (!low_delay) {
		if (mpeg2dec->first) {
		    mpeg2dec->info.display_picture = NULL;
		    mpeg2dec->first = 0;
		} else {
		    mpeg2dec->info.display_picture = other;
		    if (other->nb_fields == 1)
			mpeg2dec->info.display_picture_2nd = other + 1;
		    mpeg2dec->info.display_fbuf = mpeg2dec->fbuf[1];
		}
	    }
	    if (!low_delay + !mpeg2dec->convert)
		mpeg2dec->info.discard_fbuf =
		    mpeg2dec->fbuf[!low_delay + !mpeg2dec->convert];
	}
	if (mpeg2dec->convert) {
	    mpeg2_convert_init_t convert_init;
	    if (!mpeg2dec->convert_start) {
		int y_size, uv_size;

		mpeg2dec->decoder.convert_id =
		    mpeg2_malloc (mpeg2dec->convert_id_size,
				  MPEG2_ALLOC_CONVERT_ID);
		mpeg2dec->convert (MPEG2_CONVERT_START,
				   mpeg2dec->decoder.convert_id,
				   &(mpeg2dec->sequence),
				   mpeg2dec->convert_stride, accels,
				   mpeg2dec->convert_arg, &convert_init);
		mpeg2dec->convert_start = convert_init.start;
		mpeg2dec->decoder.convert = convert_init.copy;

		y_size = decoder->stride_frame * mpeg2dec->sequence.height;
		uv_size = y_size >> (2 - mpeg2dec->decoder.chroma_format);
		mpeg2dec->yuv_buf[0][0] =
		    (uint8_t *) mpeg2_malloc (y_size, MPEG2_ALLOC_YUV);
		mpeg2dec->yuv_buf[0][1] =
		    (uint8_t *) mpeg2_malloc (uv_size, MPEG2_ALLOC_YUV);
		mpeg2dec->yuv_buf[0][2] =
		    (uint8_t *) mpeg2_malloc (uv_size, MPEG2_ALLOC_YUV);
		mpeg2dec->yuv_buf[1][0] =
		    (uint8_t *) mpeg2_malloc (y_size, MPEG2_ALLOC_YUV);
		mpeg2dec->yuv_buf[1][1] =
		    (uint8_t *) mpeg2_malloc (uv_size, MPEG2_ALLOC_YUV);
		mpeg2dec->yuv_buf[1][2] =
		    (uint8_t *) mpeg2_malloc (uv_size, MPEG2_ALLOC_YUV);
		y_size = decoder->stride_frame * 32;
		uv_size = y_size >> (2 - mpeg2dec->decoder.chroma_format);
		mpeg2dec->yuv_buf[2][0] =
		    (uint8_t *) mpeg2_malloc (y_size, MPEG2_ALLOC_YUV);
		mpeg2dec->yuv_buf[2][1] =
		    (uint8_t *) mpeg2_malloc (uv_size, MPEG2_ALLOC_YUV);
		mpeg2dec->yuv_buf[2][2] =
		    (uint8_t *) mpeg2_malloc (uv_size, MPEG2_ALLOC_YUV);
	    }
	    if (!mpeg2dec->custom_fbuf) {
		while (mpeg2dec->alloc_index < 3) {
		    mpeg2_fbuf_t * fbuf;

		    fbuf = &mpeg2dec->fbuf_alloc[mpeg2dec->alloc_index++].fbuf;
		    fbuf->id = NULL;
		    fbuf->buf[0] =
			(uint8_t *) mpeg2_malloc (convert_init.buf_size[0],
						  MPEG2_ALLOC_CONVERTED);
		    fbuf->buf[1] =
			(uint8_t *) mpeg2_malloc (convert_init.buf_size[1],
						  MPEG2_ALLOC_CONVERTED);
		    fbuf->buf[2] =
			(uint8_t *) mpeg2_malloc (convert_init.buf_size[2],
						  MPEG2_ALLOC_CONVERTED);
		}
		mpeg2_set_fbuf (mpeg2dec, (decoder->coding_type == B_TYPE));
	    }
	} else if (!mpeg2dec->custom_fbuf) {
	    while (mpeg2dec->alloc_index < 3) {
		mpeg2_fbuf_t * fbuf;
		int y_size, uv_size;

		fbuf = &(mpeg2dec->fbuf_alloc[mpeg2dec->alloc_index++].fbuf);
		fbuf->id = NULL;
		y_size = decoder->stride_frame * mpeg2dec->sequence.height;
		uv_size = y_size >> (2 - decoder->chroma_format);
		fbuf->buf[0] = (uint8_t *) mpeg2_malloc (y_size,
							 MPEG2_ALLOC_YUV);
		fbuf->buf[1] = (uint8_t *) mpeg2_malloc (uv_size,
							 MPEG2_ALLOC_YUV);
		fbuf->buf[2] = (uint8_t *) mpeg2_malloc (uv_size,
							 MPEG2_ALLOC_YUV);
	    }
	    mpeg2_set_fbuf (mpeg2dec, (decoder->coding_type == B_TYPE));
	}
    } else {
	decoder->second_field = 1;
	mpeg2dec->picture++;	/* second field picture */
	*(mpeg2dec->picture) = mpeg2dec->new_picture;
	mpeg2dec->info.current_picture_2nd = mpeg2dec->picture;
	if (low_delay || decoder->coding_type == B_TYPE)
	    mpeg2dec->info.display_picture_2nd = mpeg2dec->picture;
    }

    info_user_data (mpeg2dec);
}

static int copyright_ext (mpeg2dec_t * mpeg2dec)
{
    return 0;
}

static int quant_matrix_ext (mpeg2dec_t * mpeg2dec)
{
    uint8_t * buffer = mpeg2dec->chunk_start;
    int i, j;

    for (i = 0; i < 4; i++)
	if (buffer[0] & (8 >> i)) {
	    for (j = 0; j < 64; j++)
		mpeg2dec->new_quantizer_matrix[i][mpeg2_scan_norm[j]] =
		    (buffer[j] << (i+5)) | (buffer[j+1] >> (3-i));
	    mpeg2dec->copy_matrix |= 1 << i;
	    buffer += 64;
	}

    return 0;
}

int mpeg2_header_extension (mpeg2dec_t * mpeg2dec)
{
    static int (* parser[]) (mpeg2dec_t *) = {
	0, sequence_ext, sequence_display_ext, quant_matrix_ext,
	copyright_ext, 0, 0, picture_display_ext, picture_coding_ext
    };
    int ext, ext_bit;

    ext = mpeg2dec->chunk_start[0] >> 4;
    ext_bit = 1 << ext;

    if (!(mpeg2dec->ext_state & ext_bit))
	return 0;	/* ignore illegal extensions */
    mpeg2dec->ext_state &= ~ext_bit;
    return parser[ext] (mpeg2dec);
}

int mpeg2_header_user_data (mpeg2dec_t * mpeg2dec)
{
    mpeg2dec->user_data_len += mpeg2dec->chunk_ptr - 1 - mpeg2dec->chunk_start;
    mpeg2dec->chunk_start = mpeg2dec->chunk_ptr - 1;
    
    return 0;
}

static void prescale (mpeg2dec_t * mpeg2dec, int index)
{
    static int non_linear_scale [] = {
	 0,  1,  2,  3,  4,  5,   6,   7,
	 8, 10, 12, 14, 16, 18,  20,  22,
	24, 28, 32, 36, 40, 44,  48,  52,
	56, 64, 72, 80, 88, 96, 104, 112
    };
    int i, j, k;
    mpeg2_decoder_t * decoder = &(mpeg2dec->decoder);

    if (mpeg2dec->scaled[index] != mpeg2dec->q_scale_type) {
	mpeg2dec->scaled[index] = mpeg2dec->q_scale_type;
	for (i = 0; i < 32; i++) {
	    k = mpeg2dec->q_scale_type ? non_linear_scale[i] : (i << 1);
	    for (j = 0; j < 64; j++)
		decoder->quantizer_prescale[index][i][j] =
		    k * mpeg2dec->quantizer_matrix[index][j];
	}
    }
}

mpeg2_state_t mpeg2_header_slice_start (mpeg2dec_t * mpeg2dec)
{
    mpeg2_decoder_t * decoder = &(mpeg2dec->decoder);

    mpeg2dec->info.user_data = NULL;	mpeg2dec->info.user_data_len = 0;
    mpeg2dec->state = ((mpeg2dec->picture->nb_fields > 1 ||
			mpeg2dec->state == STATE_PICTURE_2ND) ?
		       STATE_SLICE : STATE_SLICE_1ST);

    if (mpeg2dec->decoder.coding_type != D_TYPE) {
	prescale (mpeg2dec, 0);
	if (decoder->chroma_quantizer[0] == decoder->quantizer_prescale[2])
	    prescale (mpeg2dec, 2);
	if (mpeg2dec->decoder.coding_type != I_TYPE) {
	    prescale (mpeg2dec, 1);
	    if (decoder->chroma_quantizer[1] == decoder->quantizer_prescale[3])
		prescale (mpeg2dec, 3);
	}
    }

    if (!(mpeg2dec->nb_decode_slices))
	mpeg2dec->picture->flags |= PIC_FLAG_SKIP;
    else if (mpeg2dec->convert_start) {
	mpeg2dec->convert_start (decoder->convert_id, mpeg2dec->fbuf[0],
				 mpeg2dec->picture, mpeg2dec->info.gop);

	if (mpeg2dec->decoder.coding_type == B_TYPE)
	    mpeg2_init_fbuf (&(mpeg2dec->decoder), mpeg2dec->yuv_buf[2],
			     mpeg2dec->yuv_buf[mpeg2dec->yuv_index ^ 1],
			     mpeg2dec->yuv_buf[mpeg2dec->yuv_index]);
	else {
	    mpeg2_init_fbuf (&(mpeg2dec->decoder),
			     mpeg2dec->yuv_buf[mpeg2dec->yuv_index ^ 1],
			     mpeg2dec->yuv_buf[mpeg2dec->yuv_index],
			     mpeg2dec->yuv_buf[mpeg2dec->yuv_index]);
	    if (mpeg2dec->state == STATE_SLICE)
		mpeg2dec->yuv_index ^= 1;
	}
    } else {
	int b_type;

	b_type = (mpeg2dec->decoder.coding_type == B_TYPE);
	mpeg2_init_fbuf (&(mpeg2dec->decoder), mpeg2dec->fbuf[0]->buf,
			 mpeg2dec->fbuf[b_type + 1]->buf,
			 mpeg2dec->fbuf[b_type]->buf);
    }
    mpeg2dec->action = NULL;
    return (mpeg2_state_t)-1;
}

static mpeg2_state_t seek_sequence (mpeg2dec_t * mpeg2dec)
{
    mpeg2_reset_info (&(mpeg2dec->info));
    mpeg2dec->info.sequence = NULL;
    mpeg2dec->info.gop = NULL;
    mpeg2_header_state_init (mpeg2dec);
    mpeg2dec->action = mpeg2_seek_header;
    return mpeg2_seek_header (mpeg2dec);
}

mpeg2_state_t mpeg2_header_end (mpeg2dec_t * mpeg2dec)
{
    mpeg2_picture_t * picture;
    int b_type;

    b_type = (mpeg2dec->decoder.coding_type == B_TYPE);
    picture = mpeg2dec->pictures;
    if ((mpeg2dec->picture >= picture + 2) ^ b_type)
	picture = mpeg2dec->pictures + 2;

    mpeg2_reset_info (&(mpeg2dec->info));
    if (!(mpeg2dec->sequence.flags & SEQ_FLAG_LOW_DELAY)) {
	mpeg2dec->info.display_picture = picture;
	if (picture->nb_fields == 1)
	    mpeg2dec->info.display_picture_2nd = picture + 1;
	mpeg2dec->info.display_fbuf = mpeg2dec->fbuf[b_type];
	if (!mpeg2dec->convert)
	    mpeg2dec->info.discard_fbuf = mpeg2dec->fbuf[b_type + 1];
    } else if (!mpeg2dec->convert)
	mpeg2dec->info.discard_fbuf = mpeg2dec->fbuf[b_type];
    mpeg2dec->action = seek_sequence;
    return STATE_END;
}