mpegconsts.c

Motion JPEG编解码器源代码

/*
 *  mpegconsts.c:  Video format constants for MPEG and utilities for display
 *                 and conversion to format used for yuv4mpeg
 *
 *  Copyright (C) 2001 Andrew Stevens <[e-mail]>
 *  Copyright (C) 2001 Matthew Marjanovic <[e-mail]>
 *
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of version 2 of the GNU General Public License
 *  as published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

#include <config.h>
#include "mpegconsts.h"
#include "yuv4mpeg.h"
#include "yuv4mpeg_intern.h"

static y4m_ratio_t
mpeg_framerates[] = {
  Y4M_FPS_UNKNOWN,
  Y4M_FPS_NTSC_FILM,
  Y4M_FPS_FILM,
  Y4M_FPS_PAL,
  Y4M_FPS_NTSC,
  Y4M_FPS_30,
  Y4M_FPS_PAL_FIELD,
  Y4M_FPS_NTSC_FIELD,
  Y4M_FPS_60
};


#define MPEG_NUM_RATES (sizeof(mpeg_framerates)/sizeof(mpeg_framerates[0]))
static const mpeg_framerate_code_t mpeg_num_framerates = MPEG_NUM_RATES;

static const char *
framerate_definitions[MPEG_NUM_RATES] =
{
   "illegal", 
  "24000.0/1001.0 (NTSC 3:2 pulldown converted FILM)",
  "24.0 (NATIVE FILM)",
  "25.0 (PAL/SECAM VIDEO / converted FILM)",
  "30000.0/1001.0 (NTSC VIDEO)",
  "30.0",
  "50.0 (PAL FIELD RATE)",
  "60000.0/1001.0 (NTSC FIELD RATE)",
  "60.0"
};


static const char *mpeg1_aspect_ratio_definitions[] =
{
    "illegal",
	"1:1 (square pixels)",
	"1:0.6735",
	"1:0.7031 (16:9 Anamorphic PAL/SECAM for 720x578/352x288 images)",
	"1:0.7615",
	"1:0.8055",
	"1:0.8437 (16:9 Anamorphic NTSC for 720x480/352x240 images)",
	"1:0.8935",
	"1:0.9375 (4:3 PAL/SECAM for 720x578/352x288 images)",
	"1:0.9815",
	"1:1.0255",
	"1:1:0695",
	"1:1.1250 (4:3 NTSC for 720x480/352x240 images)",
	"1:1.1575",
	"1:1.2015"
};

static const y4m_ratio_t mpeg1_aspect_ratios[] =
{
    Y4M_SAR_UNKNOWN,
	Y4M_SAR_MPEG1_1,
	Y4M_SAR_MPEG1_2,
	Y4M_SAR_MPEG1_3, /* Anamorphic 16:9 PAL */
	Y4M_SAR_MPEG1_4,
	Y4M_SAR_MPEG1_5,
	Y4M_SAR_MPEG1_6, /* Anamorphic 16:9 NTSC */
	Y4M_SAR_MPEG1_7,
	Y4M_SAR_MPEG1_8, /* PAL/SECAM 4:3 */
	Y4M_SAR_MPEG1_9,
	Y4M_SAR_MPEG1_10,
	Y4M_SAR_MPEG1_11,
	Y4M_SAR_MPEG1_12, /* NTSC 4:3 */
	Y4M_SAR_MPEG1_13,
	Y4M_SAR_MPEG1_14,
};

static const char *mpeg2_aspect_ratio_definitions[] = 
{
    "illegal",
	"1:1 pixels",
	"4:3 display",
	"16:9 display",
	"2.21:1 display"
};


static const y4m_ratio_t mpeg2_aspect_ratios[] =
{
    Y4M_DAR_UNKNOWN,
	Y4M_DAR_MPEG2_1,
	Y4M_DAR_MPEG2_2,
 	Y4M_DAR_MPEG2_3,
	Y4M_DAR_MPEG2_4
};

static const char **aspect_ratio_definitions[2] = 
{
	mpeg1_aspect_ratio_definitions,
	mpeg2_aspect_ratio_definitions
};

static const y4m_ratio_t *mpeg_aspect_ratios[2] = 
{
	mpeg1_aspect_ratios,
	mpeg2_aspect_ratios
};

static const mpeg_aspect_code_t mpeg_num_aspect_ratios[2] = 
{
  sizeof(mpeg1_aspect_ratios)/sizeof(mpeg1_aspect_ratios[0]),
  sizeof(mpeg2_aspect_ratios)/sizeof(mpeg2_aspect_ratios[0])
};


/*
 * Is code a valid MPEG framerate code?
 */

int
mpeg_valid_framerate_code( mpeg_framerate_code_t code )
{
    return ((code > 0) && (code < mpeg_num_framerates)) ? 1 : 0;
}


/*
 * Convert MPEG frame-rate code to corresponding frame-rate
 */

y4m_ratio_t
mpeg_framerate( mpeg_framerate_code_t code )
{
    if ((code > 0) && (code < mpeg_num_framerates))
		return mpeg_framerates[code];
    else
		return y4m_fps_UNKNOWN;
}

/*
 * Look-up MPEG frame rate code for a (exact) frame rate.
 */


mpeg_framerate_code_t 
mpeg_framerate_code( y4m_ratio_t framerate )
{
	mpeg_framerate_code_t i;
  
	y4m_ratio_reduce(&framerate);
    /* start at '1', because 0 is unknown/illegal */
	for (i = 1; i < mpeg_num_framerates; ++i) {
		if (Y4M_RATIO_EQL(framerate, mpeg_framerates[i]))
			return i;
	}
	return 0;
}


/* small enough to distinguish 1/1000 from 1/1001 */
#define MPEG_FPS_TOLERANCE 0.0001


y4m_ratio_t
mpeg_conform_framerate( double fps )
{
	mpeg_framerate_code_t i;
	y4m_ratio_t result;

	/* try to match it to a standard frame rate */
    /* (start at '1', because 0 is unknown/illegal) */
	for (i = 1; i < mpeg_num_framerates; i++) 
	{
		double deviation = 1.0 - (Y4M_RATIO_DBL(mpeg_framerates[i]) / fps);
		if ( (deviation > -MPEG_FPS_TOLERANCE) &&
			 (deviation < +MPEG_FPS_TOLERANCE) )
			return mpeg_framerates[i];
	}
	/* no luck?  just turn it into a ratio (6 decimal place accuracy) */
	result.n = (int)((fps * 1000000.0) + 0.5);
	result.d = 1000000;
	y4m_ratio_reduce(&result);
	return result;
}

  

/*
 * Is code a valid MPEG aspect-ratio code?
 */

int
mpeg_valid_aspect_code( int version, mpeg_framerate_code_t c )
{
	if ((version == 1) || (version == 2))
        return ((c > 0) && (c < mpeg_num_aspect_ratios[version-1])) ? 1 : 0;
    else
        return 0;
}


/*
 * Convert MPEG aspect-ratio code to corresponding aspect-ratio
 */

y4m_ratio_t 
mpeg_aspect_ratio( int mpeg_version,  mpeg_aspect_code_t code )
{
	y4m_ratio_t ratio;
    if ((mpeg_version >= 1) && (mpeg_version <= 2) &&
        (code > 0) && (code < mpeg_num_aspect_ratios[mpeg_version-1]))
	{
		ratio = mpeg_aspect_ratios[mpeg_version-1][code];
		y4m_ratio_reduce(&ratio);
		return ratio;
	}
    else
		return y4m_sar_UNKNOWN;
}



/*
 * Look-up corresponding MPEG aspect ratio code given an exact aspect ratio.
 *
 * WARNING: The semantics of aspect ratio coding *changed* between
 * MPEG1 and MPEG2.  In MPEG1 it is the *pixel* aspect ratio. In
 * MPEG2 it is the (far more sensible) aspect ratio of the eventual
 * display.
 *
 */

mpeg_aspect_code_t 
mpeg_frame_aspect_code( int mpeg_version, y4m_ratio_t aspect_ratio )
{
	mpeg_aspect_code_t i;
	y4m_ratio_t red_ratio = aspect_ratio;
	y4m_ratio_reduce( &red_ratio );
	if( mpeg_version < 1 || mpeg_version > 2 )
		return 0;
    /* (start at '1', because 0 is unknown/illegal) */
	for( i = 1; i < mpeg_num_aspect_ratios[mpeg_version-1]; ++i )
	{
		y4m_ratio_t red_entry =  mpeg_aspect_ratios[mpeg_version-1][i];
		y4m_ratio_reduce( &red_entry );
		if(  Y4M_RATIO_EQL( red_entry, red_ratio) )
			return i;
	}

	return 0;
			
}



/*
 * Guess the correct MPEG aspect ratio code,
 *  given the true sample aspect ratio and frame size of a video stream
 *  (and the MPEG version, 1 or 2).
 *
 * Returns 0 if it has no good guess.
 *
 */


/* this is big enough to accommodate the difference between 720 and 704 */
#define GUESS_ASPECT_TOLERANCE 0.03

mpeg_aspect_code_t 
mpeg_guess_mpeg_aspect_code(int mpeg_version, y4m_ratio_t sampleaspect,
							int frame_width, int frame_height)
{
	if (Y4M_RATIO_EQL(sampleaspect, y4m_sar_UNKNOWN))
    {
		return 0;
    }
	switch (mpeg_version) {
	case 1:
		if (Y4M_RATIO_EQL(sampleaspect, y4m_sar_SQUARE))
		{
			return 1;
		} 
		else if (Y4M_RATIO_EQL(sampleaspect, y4m_sar_NTSC_CCIR601))
		{
			return 12;
		} 
		else if (Y4M_RATIO_EQL(sampleaspect, y4m_sar_NTSC_16_9))
		{
			return 6;
		} 
		else if (Y4M_RATIO_EQL(sampleaspect, y4m_sar_PAL_CCIR601))
		{
			return 8;
		} 
		else if (Y4M_RATIO_EQL(sampleaspect, y4m_sar_PAL_16_9))
		{
			return 3;
		} 
		return 0;
		break;
	case 2:
		if (Y4M_RATIO_EQL(sampleaspect, y4m_sar_SQUARE))
		{
			return 1;  /* '1' means square *pixels* in MPEG-2; go figure. */
		}
		else
		{
			int i;
			double true_far;  /* true frame aspect ratio */
			true_far = 
				(double)(sampleaspect.n * frame_width) /
				(double)(sampleaspect.d * frame_height);
			/* start at '2'... */
			for (i = 2; i < (int)(mpeg_num_aspect_ratios[mpeg_version-1]); i++) 
			{
				double ratio = 
					true_far / Y4M_RATIO_DBL(mpeg_aspect_ratios[mpeg_version-1][i]);
				if ( (ratio > (1.0 - GUESS_ASPECT_TOLERANCE)) &&
					 (ratio < (1.0 + GUESS_ASPECT_TOLERANCE)) )
					return i;
			}
			return 0;
		}
		break;
	default:
		return 0;
		break;
	}
}




/*
 * Guess the true sample aspect ratio of a video stream,
 *  given the MPEG aspect ratio code and the actual frame size
 *  (and the MPEG version, 1 or 2).
 *
 * Returns y4m_sar_UNKNOWN if it has no good guess.
 *
 */
y4m_ratio_t 
mpeg_guess_sample_aspect_ratio(int mpeg_version,
							   mpeg_aspect_code_t code,
							   int frame_width, int frame_height)
{
	switch (mpeg_version) 
	{
	case 1:
		/* MPEG-1 codes turn into SAR's, just not quite the right ones.
		   For the common/known values, we provide the ratio used in practice,
		   otherwise say we don't know.*/
		switch (code)
		{
		case 1:  return y4m_sar_SQUARE;        break;
		case 3:  return y4m_sar_PAL_16_9;      break;
		case 6:  return y4m_sar_NTSC_16_9;     break;
		case 8:  return y4m_sar_PAL_CCIR601;   break;
		case 12: return y4m_sar_NTSC_CCIR601;  break;
		default:
			return y4m_sar_UNKNOWN;       break;
		}
		break;
	case 2:
		/* MPEG-2 codes turn into Display Aspect Ratios, though not exactly the
		   DAR's used in practice.  For common/standard frame sizes, we provide
		   the original SAR; otherwise, we say we don't know. */
		if (code == 1) 
		{
			return y4m_sar_SQUARE; /* '1' means square *pixels* in MPEG-2 */
		}
		else if ((code >= 2) && (code <= 4))
		{
            return y4m_guess_sar(frame_width, frame_height,
                                 mpeg2_aspect_ratios[code]);
		} 
		else
		{
			return y4m_sar_UNKNOWN;
		}
		break;
	default:
		return y4m_sar_UNKNOWN;
		break;
	}
}





/*
 * Look-up MPEG explanatory definition string for frame rate code
 *
 */


const char *
mpeg_framerate_code_definition(   mpeg_framerate_code_t code  )
{
	if( code == 0 || code >=  mpeg_num_framerates )
		return "UNDEFINED: illegal/reserved frame-rate ratio code";

	return framerate_definitions[code];
}

/*
 * Look-up MPEG explanatory definition string aspect ratio code for an
 * aspect ratio code
 *
 */

const char *
mpeg_aspect_code_definition( int mpeg_version,  mpeg_aspect_code_t code  )
{
	if( mpeg_version < 1 || mpeg_version > 2 )
		return "UNDEFINED: illegal MPEG version";
	
	if( code < 1 || code >=  mpeg_num_aspect_ratios[mpeg_version-1] )
		return "UNDEFINED: illegal aspect ratio code";

	return aspect_ratio_definitions[mpeg_version-1][code];
}


/*
 * Look-up explanatory definition of interlace field order code
 *
 */

const char *
mpeg_interlace_code_definition( int yuv4m_interlace_code )
{
	const char *def;
	switch( yuv4m_interlace_code )
	{
	case Y4M_UNKNOWN :
		def = "unknown";
		break;
	case Y4M_ILACE_NONE :
		def = "none/progressive";
		break;
	case Y4M_ILACE_TOP_FIRST :
		def = "top-field-first";
		break;
	case Y4M_ILACE_BOTTOM_FIRST :
		def = "bottom-field-first";
		break;
	default :
		def = "UNDEFINED: illegal video interlacing type-code!";
		break;
	}
	return def;
}


/* 
 * Local variables:
 *  c-file-style: "stroustrup"
 *  tab-width: 4
 *  indent-tabs-mode: nil
 * End:
 */