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a6c5893732
mame/src/lib/util/vbiparse.c
Aaron Giles a6c5893732 Assert copyright ownership of core library files, and relicense 
under standard BSD license.
2009-10-09 05:25:04 +00:00

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/***************************************************************************
vbiparse.c
Parse Philips codes and other data from VBI lines.
****************************************************************************
Copyright Aaron Giles
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
* Neither the name 'MAME' nor the names of its contributors may be
used to endorse or promote products derived from this software
without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY AARON GILES ''AS IS'' AND ANY EXPRESS OR
IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL AARON GILES BE LIABLE FOR ANY DIRECT,
INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
***************************************************************************/
#include "osdcore.h"
#include "vbiparse.h"
#include <math.h>
/***************************************************************************
DEBUGGING
***************************************************************************/
#define PRINTF_WHITE_FLAG 0
/***************************************************************************
CONSTANTS
***************************************************************************/
#define MAX_SOURCE_WIDTH 1024
#define MAX_CLOCK_DIFF 3
/***************************************************************************
IMPLEMENTATION
***************************************************************************/
/*-------------------------------------------------
vbi_parse_manchester_code - parse a Manchester
code from a line of video data
-------------------------------------------------*/
int vbi_parse_manchester_code(const UINT16 *source, int sourcewidth, int sourceshift, int expectedbits, UINT32 *result)
{
UINT8 srcabs[MAX_SOURCE_WIDTH];
UINT8 min, max, mid, srcabsval;
double clock, bestclock;
int x, firstedge;
int besterr;
/* fail if the width is too large */
if (sourcewidth > MAX_SOURCE_WIDTH)
return 0;
/* find highs and lows in the line */
min = 0xff;
max = 0x00;
for (x = 0; x < sourcewidth; x++)
{
UINT8 rawsrc = source[x] >> sourceshift;
min = MIN(min, rawsrc);
max = MAX(max, rawsrc);
}
/* bail if the line is all black or all white */
if (max < 0x80 || min > 0x80)
return 0;
/* determine the midpoint and then set the thresholds to be halfway */
mid = (min + max) / 2;
min = mid - (mid - min) / 2;
max = mid + (max - mid) / 2;
/* convert the source into absolute high/low */
srcabsval = (source[0] > mid);
for (x = 0; x < sourcewidth; x++)
{
UINT8 rawsrc = source[x] >> sourceshift;
if (rawsrc >= max)
srcabsval = 1;
else if (rawsrc <= min)
srcabsval = 0;
srcabs[x] = srcabsval;
}
/* find the first transition; this is assumed to be the middle of the first bit */
for (x = 0; x < sourcewidth - 1; x++)
if (srcabs[x] != srcabs[x + 1])
break;
if (x == sourcewidth - 1)
return 0;
firstedge = x;
/* now scan to find a clock that has a nearby transition on each beat */
bestclock = 0;
besterr = 1000;
for (clock = (double)sourcewidth / (double)expectedbits; clock >= 2.0; clock -= 1.0 / (double)expectedbits)
{
int error = 0;
/* scan for all the expected bits */
for (x = 1; x < expectedbits; x++)
{
int curbit = firstedge + (double)x * clock;
int offby;
/* look for a match that is off by an amount up to the maximum */
for (offby = 0; offby <= MAX_CLOCK_DIFF; offby++)
if (srcabs[curbit + offby + 0] != srcabs[curbit + offby + 1] || srcabs[curbit - offby + 0] != srcabs[curbit - offby + 1])
break;
/* if we never found the edge, fail immediately */
if (offby > MAX_CLOCK_DIFF)
break;
/* only continue if we're still in the running */
error += offby;
if (error >= besterr)
break;
}
/* if we got to the end, this is the best candidate so far */
if (x == expectedbits)
{
besterr = error;
bestclock = clock;
}
}
/* if nobody matched, fail */
if (bestclock == 0)
return 0;
/* now extract the bits */
for (x = 0; x < expectedbits; x++)
{
int leftstart = firstedge + ceil(((double)x - 0.5) * bestclock);
// int leftmid = firstedge + ((double)x - 0.25) * bestclock;
int leftend = firstedge + floor(((double)x - 0.0) * bestclock);
int rightstart = firstedge + ceil(((double)x + 0.0) * bestclock);
// int rightmid = firstedge + ((double)x + 0.25) * bestclock;
int rightend = firstedge + floor(((double)x + 0.5) * bestclock);
int leftavg, rightavg, leftabs, rightabs;
int confidence = 0;
int tx;
/* compute left and right average values */
leftavg = 0;
for (tx = leftstart; tx <= leftend; tx++)
leftavg += (UINT8)(source[tx] >> sourceshift) - mid;
leftabs = (leftavg >= 0);
leftavg = (leftavg < 0) ? -leftavg : leftavg;
rightavg = 0;
for (tx = rightstart; tx <= rightend; tx++)
rightavg += (UINT8)(source[tx] >> sourceshift) - mid;
rightabs = (rightavg >= 0);
rightavg = (rightavg < 0) ? -rightavg : rightavg;
/* all bits should be marked by transitions; fail if we don't get one */
if (leftabs == rightabs)
return 0;
/* store the bit and its confidence level */
confidence = leftavg + rightavg;
result[x] = (leftabs < rightabs) | (confidence << 1);
}
return expectedbits;
}
/*-------------------------------------------------
vbi_parse_white_flag - compute the "white
flag" from a line of video data
-------------------------------------------------*/
int vbi_parse_white_flag(const UINT16 *source, int sourcewidth, int sourceshift)
{
int histo[256] = { 0 };
int minval = 0xff;
int maxval = 0x00;
int subtract;
int peakval;
int result;
int x;
/* compute a histogram of values */
for (x = 0; x < sourcewidth; x++)
{
UINT8 yval = source[x] >> sourceshift;
histo[yval]++;
}
/* remove the lowest 1% of the values to account for noise and determine the minimum */
subtract = sourcewidth / 100;
for (minval = 0; minval < 255; minval++)
if ((subtract -= histo[minval]) < 0)
break;
/* remove the highest 1% of the values to account for noise and determine the maximum */
subtract = sourcewidth / 100;
for (maxval = 255; maxval > 0; maxval--)
if ((subtract -= histo[maxval]) < 0)
break;
/* this is useful for debugging issues with white flag detection */
if (PRINTF_WHITE_FLAG)
{
printf("Histo: min=%02X max=%02X\n", minval, maxval);
for (x = 0; x < 256; x++)
if (histo[x] != 0) printf("%dx%02X\n", histo[x], x);
}
/* ignore if we have no dynamic range */
if (maxval - minval < 10)
{
if (PRINTF_WHITE_FLAG)
printf("White flag NOT detected; threshold too low\n");
return FALSE;
}
/*
At this point, there are two approaches that have been tried:
1. Find the peak value and call it white if the peak is above
the 90% line
2. Ignore the first and last 20% of the line and count how
many pixels are above some threshold (75% line was used).
Call it white if at least 80% of the pixels are above
the threshold.
Both approaches agree 99% of the time, but the first tends to
be more correct when there is a discrepancy.
*/
/* determine where the peak is */
peakval = 0;
for (x = 1; x < 256; x++)
if (histo[x] > histo[peakval])
peakval = x;
/* return TRUE if it is above the 90% mark */
result = (peakval > minval + 9 * (maxval - minval) / 10);
if (PRINTF_WHITE_FLAG)
printf("White flag %s: peak=%02X thresh=%02X\n", result ? "detected" : "NOT detected", peakval, minval + 9 * (maxval - minval) / 10);
return result;
#ifdef UNUSED_CODE
{
int above = 0;
int thresh;
/* alternate approach: */
/* ignore the first 1/5 and last 1/5 of the line for the remaining computations */
source += sourcewidth / 5;
sourcewidth -= 2 * (sourcewidth / 5);
/* count how many values were above the 75% mark of the range */
thresh = minval + 3 * (maxval - minval) / 4;
for (x = 0; x < sourcewidth; x++)
{
UINT8 yval = source[x] >> sourceshift;
above += (yval >= thresh);
}
/* if at least 80% of the pixels are above the threshold, we'll call it white */
return ((above * 100) / sourcewidth >= 80);
}
#endif
}
/*-------------------------------------------------
vbi_parse_all - parse everything from a video
frame
-------------------------------------------------*/
void vbi_parse_all(const UINT16 *source, int sourcerowpixels, int sourcewidth, int sourceshift, vbi_metadata *vbi)
{
UINT32 bits[2][24];
UINT8 bitnum;
/* first reset it all */
memset(vbi, 0, sizeof(*vbi));
/* get the white flag */
vbi->white = vbi_parse_white_flag(source + 11 * sourcerowpixels, sourcewidth, sourceshift);
/* parse line 16 */
if (vbi_parse_manchester_code(source + 16 * sourcerowpixels, sourcewidth, sourceshift, 24, bits[0]) == 24)
for (bitnum = 0; bitnum < 24; bitnum++)
vbi->line16 = (vbi->line16 << 1) | (bits[0][bitnum] & 1);
/* parse line 17 */
if (vbi_parse_manchester_code(source + 17 * sourcerowpixels, sourcewidth, sourceshift, 24, bits[0]) == 24)
for (bitnum = 0; bitnum < 24; bitnum++)
vbi->line17 = (vbi->line17 << 1) | (bits[0][bitnum] & 1);
/* parse line 18 */
if (vbi_parse_manchester_code(source + 18 * sourcerowpixels, sourcewidth, sourceshift, 24, bits[1]) == 24)
for (bitnum = 0; bitnum < 24; bitnum++)
vbi->line18 = (vbi->line18 << 1) | (bits[1][bitnum] & 1);
/* pick the best out of lines 17/18 */
/* if we only got one or the other, that's all we have */
if (vbi->line17 == 0)
vbi->line1718 = vbi->line18;
else if (vbi->line18 == 0)
vbi->line1718 = vbi->line17;
/* if they agree, we're golden */
else if (vbi->line17 == vbi->line18)
vbi->line1718 = vbi->line17;
/* if they don't agree, we have to pick one */
else
{
/* if both are frame numbers, and one is not valid BCD, pick the other */
if ((vbi->line17 & VBI_MASK_CAV_PICTURE) == VBI_CODE_CAV_PICTURE && (vbi->line18 & VBI_MASK_CAV_PICTURE) == VBI_CODE_CAV_PICTURE)
{
if ((vbi->line17 & 0xf000) > 0x9000 || (vbi->line17 & 0xf00) > 0x900 || (vbi->line17 & 0xf0) > 0x90 || (vbi->line17 & 0xf) > 0x9)
vbi->line1718 = vbi->line18;
else if ((vbi->line18 & 0xf000) > 0x9000 || (vbi->line18 & 0xf00) > 0x900 || (vbi->line18 & 0xf0) > 0x90 || (vbi->line18 & 0xf) > 0x9)
vbi->line1718 = vbi->line17;
}
/* if still nothing, then scan through the bits and pick the ones with the most confidence */
if (vbi->line1718 == 0)
for (bitnum = 0; bitnum < 24; bitnum++)
vbi->line1718 = (vbi->line1718 << 1) | ((bits[0][bitnum] > bits[1][bitnum]) ? (bits[0][bitnum] & 1) : (bits[1][bitnum] & 1));
}
}
/*-------------------------------------------------
vbi_metadata_pack - pack the VBI data down
into a smaller form for storage
-------------------------------------------------*/
void vbi_metadata_pack(UINT8 *dest, UINT32 framenum, const vbi_metadata *vbi)
{
dest[0] = framenum >> 16;
dest[1] = framenum >> 8;
dest[2] = framenum >> 0;
dest[3] = vbi->white;
dest[4] = vbi->line16 >> 16;
dest[5] = vbi->line16 >> 8;
dest[6] = vbi->line16 >> 0;
dest[7] = vbi->line17 >> 16;
dest[8] = vbi->line17 >> 8;
dest[9] = vbi->line17 >> 0;
dest[10] = vbi->line18 >> 16;
dest[11] = vbi->line18 >> 8;
dest[12] = vbi->line18 >> 0;
dest[13] = vbi->line1718 >> 16;
dest[14] = vbi->line1718 >> 8;
dest[15] = vbi->line1718 >> 0;
}
/*-------------------------------------------------
vbi_metadata_unpack - unpack the VBI data
from a smaller form into the full structure
-------------------------------------------------*/
void vbi_metadata_unpack(vbi_metadata *vbi, UINT32 *framenum, const UINT8 *source)
{
if (framenum != NULL)
*framenum = (source[0] << 16) | (source[1] << 8) | source[2];
vbi->white = source[3];
vbi->line16 = (source[4] << 16) | (source[5] << 8) | source[6];
vbi->line17 = (source[7] << 16) | (source[8] << 8) | source[9];
vbi->line18 = (source[10] << 16) | (source[11] << 8) | source[12];
vbi->line1718 = (source[13] << 16) | (source[14] << 8) | source[15];
}
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