rockbox/apps/plugins/mpegplayer/header.c

/*
 * header.c
 * Copyright (C) 2000-2003 Michel Lespinasse <walken@zoy.org>
 * Copyright (C) 2003      Regis Duchesne <hpreg@zoy.org>
 * Copyright (C) 1999-2000 Aaron Holtzman <aholtzma@ess.engr.uvic.ca>
 *
 * This file is part of mpeg2dec, a free MPEG-2 video stream decoder.
 * See http://libmpeg2.sourceforge.net/ for updates.
 *
 * mpeg2dec is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * mpeg2dec 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
 *
 * $Id$
 * libmpeg2 sync history:
 * 2008-07-01 - CVS revision 1.101
 */

#include "plugin.h"

#include "mpeg2dec_config.h"

extern const struct plugin_api* rb;

#include "mpeg2.h"
#include "attributes.h"
#include "mpeg2_internal.h"

#define SEQ_EXT 2
#define SEQ_DISPLAY_EXT 4
#define QUANT_MATRIX_EXT 8
#define COPYRIGHT_EXT 0x10
#define PIC_DISPLAY_EXT 0x80
#define PIC_CODING_EXT 0x100

/* default intra quant matrix, in zig-zag order */
static const uint8_t default_intra_quantizer_matrix[64] =
{
    8,
    16, 16,
    19, 16, 19,
    22, 22, 22, 22,
    22, 22, 26, 24, 26,
    27, 27, 27, 26, 26, 26,
    26, 27, 27, 27, 29, 29, 29,
    34, 34, 34, 29, 29, 29, 27, 27,
    29, 29, 32, 32, 34, 34, 37,
    38, 37, 35, 35, 34, 35,
    38, 38, 40, 40, 40,
    48, 48, 46, 46,
    56, 56, 58,
    69, 69,
    83
};

const uint8_t default_mpeg2_scan_norm[64] =
{
    /* Zig-Zag scan pattern */
     0,  1,  8, 16,  9,  2,  3, 10,
    17, 24, 32, 25, 18, 11,  4,  5,
    12, 19, 26, 33, 40, 48, 41, 34,
    27, 20, 13,  6,  7, 14, 21, 28,
    35, 42, 49, 56, 57, 50, 43, 36,
    29, 22, 15, 23, 30, 37, 44, 51,
    58, 59, 52, 45, 38, 31, 39, 46,
    53, 60, 61, 54, 47, 55, 62, 63
};

const uint8_t default_mpeg2_scan_alt[64] =
{
    /* Alternate scan pattern */
     0, 8,  16, 24,  1,  9,  2, 10,
    17, 25, 32, 40, 48, 56, 57, 49,
    41, 33, 26, 18,  3, 11,  4, 12,
    19, 27, 34, 42, 50, 58, 35, 43,
    51, 59, 20, 28,  5, 13,  6, 14,
    21, 29, 36, 44, 52, 60, 37, 45,
    53, 61, 22, 30,  7, 15, 23, 31,
    38, 46, 54, 62, 39, 47, 55, 63
};

uint8_t mpeg2_scan_norm[64] IDATA_ATTR;
uint8_t mpeg2_scan_alt[64] IDATA_ATTR;

void mpeg2_header_state_init (mpeg2dec_t * mpeg2dec)
{
    if (mpeg2dec->sequence.width != (unsigned)-1)
    {
        mpeg2dec->sequence.width = (unsigned)-1;
        mpeg2_mem_reset(); /* Clean the memory slate */
#if 0
        if (!mpeg2dec->custom_fbuf)
        {
            int i;
            for (i = mpeg2dec->alloc_index_user;
                 i < mpeg2dec->alloc_index; i++)
            {
                mpeg2_free(mpeg2dec->fbuf_alloc[i].fbuf.buf[0]);
#if MPEG2_COLOR
                mpeg2_free(mpeg2dec->fbuf_alloc[i].fbuf.buf[1]);
                mpeg2_free(mpeg2dec->fbuf_alloc[i].fbuf.buf[2]);
#endif
            }
        }

        if (mpeg2dec->convert_start)
        {
            int i;
            for (i = 0; i < 3; i++)
            {
                mpeg2_free(mpeg2dec->yuv_buf[i][0]);
#if MPEG2_COLOR
                mpeg2_free(mpeg2dec->yuv_buf[i][1]);
                mpeg2_free(mpeg2dec->yuv_buf[i][2]);
#endif
            }
        }

        if (mpeg2dec->decoder.convert_id)
        {
            mpeg2_free(mpeg2dec->decoder.convert_id);
        }
#endif
    }

    mpeg2dec->decoder.coding_type = I_TYPE;
    mpeg2dec->decoder.convert = NULL;
    mpeg2dec->decoder.convert_id = NULL;

    mpeg2dec->picture = mpeg2dec->pictures;

    mpeg2dec->fbuf[0] = &mpeg2dec->fbuf_alloc[0].fbuf;
    mpeg2dec->fbuf[1] = &mpeg2dec->fbuf_alloc[1].fbuf;
    mpeg2dec->fbuf[2] = &mpeg2dec->fbuf_alloc[2].fbuf;

    mpeg2dec->first = 1;
    mpeg2dec->alloc_index = 0;
    mpeg2dec->alloc_index_user = 0;
    mpeg2dec->first_decode_slice = 1;
    mpeg2dec->nb_decode_slices = 0xb0 - 1;
    mpeg2dec->convert = NULL;
    mpeg2dec->convert_start = NULL;
    mpeg2dec->custom_fbuf = 0;
    mpeg2dec->yuv_index = 0;
}

void mpeg2_reset_info (mpeg2_info_t * info)
{
    info->current_picture =
    info->current_picture_2nd = NULL;

    info->display_picture =
    info->display_picture_2nd = NULL;

    info->current_fbuf =
    info->display_fbuf =
    info->discard_fbuf = NULL;
}

static void info_user_data (mpeg2dec_t * mpeg2dec)
{
    if (mpeg2dec->user_data_len)
    {
        mpeg2dec->info.user_data = mpeg2dec->chunk_buffer;
        mpeg2dec->info.user_data_len = mpeg2dec->user_data_len - 3;
    }
}

int mpeg2_header_sequence (mpeg2dec_t * mpeg2dec)
{
    static const unsigned int frame_period[16] =
    {
        0, 1126125, 1125000, 1080000, 900900, 900000, 540000, 450450, 450000,
        /* unofficial: xing 15 fps */
        1800000,
        /* unofficial: libmpeg3 "Unofficial economy rates" 5/10/12/15 fps */
        5400000, 2700000, 2250000, 1800000, 0, 0
    };

    uint8_t * buffer = mpeg2dec->chunk_start;
    mpeg2_sequence_t * sequence = &mpeg2dec->new_sequence;
    int i;

    if ((buffer[6] & 0x20) != 0x20)        /* missing marker_bit */
        return 1;

    i = (buffer[0] << 16) | (buffer[1] << 8) | buffer[2];

    if (!(sequence->display_width = sequence->picture_width = i >> 12))
        return 1;

    if (!(sequence->display_height = sequence->picture_height = i & 0xfff))
        return 1;

    sequence->width = (sequence->picture_width + 15) & ~15;
    sequence->height = (sequence->picture_height + 15) & ~15;
    sequence->chroma_width = sequence->width >> 1;
    sequence->chroma_height = sequence->height >> 1;

    sequence->flags = SEQ_FLAG_PROGRESSIVE_SEQUENCE |
                      SEQ_VIDEO_FORMAT_UNSPECIFIED;

    sequence->pixel_width = buffer[3] >> 4;        /* aspect ratio */
    sequence->frame_period = frame_period[buffer[3] & 15];

    sequence->byte_rate = (buffer[4]<<10) | (buffer[5]<<2) | (buffer[6]>>6);

    sequence->vbv_buffer_size = ((buffer[6]<<16) | (buffer[7]<<8)) & 0x1ff800;

    if (buffer[7] & 4)
        sequence->flags |= SEQ_FLAG_CONSTRAINED_PARAMETERS;

    mpeg2dec->copy_matrix = 3;

    if (buffer[7] & 2)
    {
        for (i = 0; i < 64; i++)
        {
            mpeg2dec->new_quantizer_matrix[0][mpeg2_scan_norm[i]] =
                (buffer[i+7] << 7) | (buffer[i+8] >> 1);
        }

        buffer += 64;
    }
    else
    {
        for (i = 0; i < 64; i++)
        {
            mpeg2dec->new_quantizer_matrix[0][mpeg2_scan_norm[i]] =
                default_intra_quantizer_matrix[i];
        }
    }

    if (buffer[7] & 1)
    {
        for (i = 0; i < 64; i++)
        {
            mpeg2dec->new_quantizer_matrix[1][mpeg2_scan_norm[i]] =
                buffer[i+8];
        }
    }
    else
    {
        rb->memset (mpeg2dec->new_quantizer_matrix[1], 16, 64);
    }

    sequence->profile_level_id = 0x80;
    sequence->colour_primaries = 0;
    sequence->transfer_characteristics = 0;
    sequence->matrix_coefficients = 0;

    mpeg2dec->ext_state = SEQ_EXT;
    mpeg2dec->state = STATE_SEQUENCE;

    mpeg2dec->display_offset_x =
    mpeg2dec->display_offset_y = 0;

    return 0;
}

static int sequence_ext (mpeg2dec_t * mpeg2dec)
{
    uint8_t * buffer = mpeg2dec->chunk_start;
    mpeg2_sequence_t * sequence = &mpeg2dec->new_sequence;
    uint32_t flags;

    if (!(buffer[3] & 1))
        return 1;

    sequence->profile_level_id = (buffer[0] << 4) | (buffer[1] >> 4);

    sequence->picture_width += ((buffer[1] << 13) | (buffer[2] << 5)) & 0x3000;
    sequence->display_width = sequence->picture_width;

    sequence->picture_height += (buffer[2] << 7) & 0x3000;
    sequence->display_height = sequence->picture_height;

    sequence->width = (sequence->picture_width + 15) & ~15;
    sequence->height = (sequence->picture_height + 15) & ~15;

    flags = sequence->flags | SEQ_FLAG_MPEG2;

    if (!(buffer[1] & 8))
    {
        flags &= ~SEQ_FLAG_PROGRESSIVE_SEQUENCE;
        sequence->height = (sequence->height + 31) & ~31;
    }

    if (buffer[5] & 0x80)
        flags |= SEQ_FLAG_LOW_DELAY;

    sequence->flags = flags;
    sequence->chroma_width = sequence->width;
    sequence->chroma_height = sequence->height;

    switch (buffer[1] & 6)
    {
    case 0:        /* invalid */
        return 1;
    case 2:        /* 4:2:0 */
        sequence->chroma_height >>= 1;
    case 4:        /* 4:2:2 */
        sequence->chroma_width >>= 1;
    }

    sequence->byte_rate += ((buffer[2]<<25) | (buffer[3]<<17)) & 0x3ffc0000;

    sequence->vbv_buffer_size |= buffer[4] << 21;

    sequence->frame_period =
        sequence->frame_period * ((buffer[5]&31)+1) / (((buffer[5]>>2)&3)+1);

    mpeg2dec->ext_state = SEQ_DISPLAY_EXT;

    return 0;
}

static int sequence_display_ext (mpeg2dec_t * mpeg2dec)
{
    uint8_t * buffer = mpeg2dec->chunk_start;
    mpeg2_sequence_t * sequence = &mpeg2dec->new_sequence;
    int x;

    sequence->flags = (sequence->flags & ~SEQ_MASK_VIDEO_FORMAT) |
             ((buffer[0] << 4) & SEQ_MASK_VIDEO_FORMAT);

    if (buffer[0] & 1)
    {
        sequence->flags |= SEQ_FLAG_COLOUR_DESCRIPTION;
        sequence->colour_primaries = buffer[1];
        sequence->transfer_characteristics = buffer[2];
        sequence->matrix_coefficients = buffer[3];
        buffer += 3;
    }

    if (!(buffer[2] & 2))        /* missing marker_bit */
        return 1;

    x = (buffer[1] << 6) | (buffer[2] >> 2);
    if (x)
        sequence->display_width = x;

    x = ((buffer[2] & 1) << 13) | (buffer[3] << 5) | (buffer[4] >> 3);
    if (x)
        sequence->display_height = x;

    return 0;
}

static inline void simplify (unsigned int * u, unsigned int * v) 
{ 
    unsigned int a, b, tmp; 
 
    a = *u;
    b = *v; 

    /* find greatest common divisor */ 
    while (a)
    {
        tmp = a;
        a = b % tmp;
        b = tmp; 
    } 

    *u /= b;
    *v /= b; 
} 

static inline void finalize_sequence (mpeg2_sequence_t * sequence)
{
    int width;
    int height;

    sequence->byte_rate *= 50;

    if (sequence->flags & SEQ_FLAG_MPEG2)
    {
        switch (sequence->pixel_width)
        {
        case 1:                /* square pixels */
            sequence->pixel_width =
            sequence->pixel_height = 1;
            return;
        case 2:                /* 4:3 aspect ratio */
            width = 4;
            height = 3;
            break;
        case 3:                /* 16:9 aspect ratio */
            width = 16;
            height = 9;
            break;
        case 4:                /* 2.21:1 aspect ratio */
            width = 221;
            height = 100;
            break;
        default:        /* illegal */
            sequence->pixel_width =
            sequence->pixel_height = 0;
            return;
        }

        width *= sequence->display_height;
        height *= sequence->display_width;
    }
    else
    {
        if (sequence->byte_rate == 50 * 0x3ffff)
            sequence->byte_rate = 0;        /* mpeg-1 VBR */

        switch (sequence->pixel_width)
        {
        case 0:
        case 15:        /* illegal */
            sequence->pixel_width =
            sequence->pixel_height = 0;
            return;
        case 1:        /* square pixels */
            sequence->pixel_width =
            sequence->pixel_height = 1;
            return;
        case 3:        /* 720x576 16:9 */
            sequence->pixel_width = 64;
            sequence->pixel_height = 45;
            return;
        case 6:        /* 720x480 16:9 */
            sequence->pixel_width = 32;
            sequence->pixel_height = 27;
            return;
        case 8:        /* BT.601 625 lines 4:3 */
            sequence->pixel_width = 59;
            sequence->pixel_height = 54;
            return;
        case 12:       /* BT.601 525 lines 4:3 */
            sequence->pixel_width = 10;
            sequence->pixel_height = 11;
            return;
        default:
            height = 88 * sequence->pixel_width + 1171;
            width = 2000;
        }
    }

    sequence->pixel_width = width;
    sequence->pixel_height = height;

    simplify(&sequence->pixel_width, &sequence->pixel_height);
}

int mpeg2_guess_aspect (const mpeg2_sequence_t * sequence, 
                        unsigned int * pixel_width, 
                        unsigned int * pixel_height) 
{ 
    static const struct
    { 
        unsigned int width, height; 
    } video_modes[] =
    {
        {720, 576}, /* 625 lines, 13.5 MHz (D1, DV, DVB, DVD) */ 
        {704, 576}, /* 625 lines, 13.5 MHz (1/1 D1, DVB, DVD, 4CIF) */ 
        {544, 576}, /* 625 lines, 10.125 MHz (DVB, laserdisc) */ 
        {528, 576}, /* 625 lines, 10.125 MHz (3/4 D1, DVB, laserdisc) */ 
        {480, 576}, /* 625 lines, 9 MHz (2/3 D1, DVB, SVCD) */ 
        {352, 576}, /* 625 lines, 6.75 MHz (D2, 1/2 D1, CVD, DVB, DVD) */ 
        {352, 288}, /* 625 lines, 6.75 MHz, 1 field (D4, VCD, DVB, DVD, CIF) */ 
        {176, 144}, /* 625 lines, 3.375 MHz, half field (QCIF) */ 
        {720, 486}, /* 525 lines, 13.5 MHz (D1) */ 
        {704, 486}, /* 525 lines, 13.5 MHz */ 
        {720, 480}, /* 525 lines, 13.5 MHz (DV, DSS, DVD) */ 
        {704, 480}, /* 525 lines, 13.5 MHz (1/1 D1, ATSC, DVD) */ 
        {544, 480}, /* 525 lines. 10.125 MHz (DSS, laserdisc) */ 
        {528, 480}, /* 525 lines. 10.125 MHz (3/4 D1, laserdisc) */ 
        {480, 480}, /* 525 lines, 9 MHz (2/3 D1, SVCD) */ 
        {352, 480}, /* 525 lines, 6.75 MHz (D2, 1/2 D1, CVD, DVD) */ 
        {352, 240}  /* 525 lines. 6.75 MHz, 1 field (D4, VCD, DSS, DVD) */ 
    }; 
    unsigned int width, height, pix_width, pix_height, i, DAR_16_9; 
 
    *pixel_width = sequence->pixel_width; 
    *pixel_height = sequence->pixel_height; 
    width = sequence->picture_width; 
    height = sequence->picture_height; 

    for (i = 0; i < sizeof (video_modes) / sizeof (video_modes[0]); i++) 
    {
        if (width == video_modes[i].width && height == video_modes[i].height) 
            break; 
    }

    if (i == ARRAYLEN(video_modes) || 
        (sequence->pixel_width == 1 && sequence->pixel_height == 1) ||
        width != sequence->display_width || height != sequence->display_height)
    {
        return 0; 
    }
 
    for (pix_height = 1; height * pix_height < 480; pix_height <<= 1);
    height *= pix_height; 

    for (pix_width = 1; width * pix_width <= 352; pix_width <<= 1); 
    width *= pix_width; 
 
    if (!(sequence->flags & SEQ_FLAG_MPEG2))
    {
        static unsigned int mpeg1_check[2][2] = {{11, 54}, {27, 45}}; 
        DAR_16_9 = (sequence->pixel_height == 27 || 
                    sequence->pixel_height == 45); 
        if (width < 704 || 
            sequence->pixel_height != mpeg1_check[DAR_16_9][height == 576]) 
            return 0; 
    }
    else
    { 
        DAR_16_9 = (3 * sequence->picture_width * sequence->pixel_width > 
                    4 * sequence->picture_height * sequence->pixel_height); 
        switch (width)
        { 
        case 528:
        case 544:
            pix_width *= 4;
            pix_height *= 3;
            break;
        case 480:
            pix_width *= 3;
            pix_height *= 2;
            break;
        } 
    }

    if (DAR_16_9)
    { 
        pix_width *= 4;
        pix_height *= 3; 
    } 

    if (height == 576)
    { 
        pix_width *= 59;
        pix_height *= 54; 
    }
    else
    { 
        pix_width *= 10;
        pix_height *= 11; 
    }

    *pixel_width = pix_width; 
    *pixel_height = pix_height;

    simplify (pixel_width, pixel_height); 

    return (height == 576) ? 1 : 2; 
} 

static void copy_matrix (mpeg2dec_t * mpeg2dec, int index)
{
    if (rb->memcmp (mpeg2dec->quantizer_matrix[index],
                mpeg2dec->new_quantizer_matrix[index], 64))
    {
        rb->memcpy (mpeg2dec->quantizer_matrix[index],
                mpeg2dec->new_quantizer_matrix[index], 64);

        mpeg2dec->scaled[index] = -1;
    }
}

static void finalize_matrix (mpeg2dec_t * mpeg2dec)
{
    mpeg2_decoder_t *decoder = &mpeg2dec->decoder;
    int i;

    for (i = 0; i < 2; i++)
    {
        if (mpeg2dec->copy_matrix & (1 << i))
            copy_matrix (mpeg2dec, i);

        if ((mpeg2dec->copy_matrix & (4 << i)) &&
            rb->memcmp(mpeg2dec->quantizer_matrix[i],
                       mpeg2dec->new_quantizer_matrix[i+2], 64))
        {
            copy_matrix (mpeg2dec, i + 2);
            decoder->chroma_quantizer[i] = decoder->quantizer_prescale[i+2];
        }
        else if (mpeg2dec->copy_matrix & (5 << i))
        {
            decoder->chroma_quantizer[i] = decoder->quantizer_prescale[i];
        }
    }
}

static mpeg2_state_t invalid_end_action (mpeg2dec_t * mpeg2dec)
{
    mpeg2_reset_info (&mpeg2dec->info);

    mpeg2dec->info.gop = NULL;

    info_user_data (mpeg2dec);

    mpeg2_header_state_init (mpeg2dec);

    mpeg2dec->sequence = mpeg2dec->new_sequence;
    mpeg2dec->action = mpeg2_seek_header;
    mpeg2dec->state = STATE_SEQUENCE;

    return STATE_SEQUENCE;
}

void mpeg2_header_sequence_finalize (mpeg2dec_t * mpeg2dec)
{
    mpeg2_sequence_t * sequence = &mpeg2dec->new_sequence;
    mpeg2_decoder_t * decoder = &mpeg2dec->decoder;

    finalize_sequence(sequence);
    finalize_matrix(mpeg2dec);

    decoder->mpeg1 = !(sequence->flags & SEQ_FLAG_MPEG2);
    decoder->width = sequence->width;
    decoder->height = sequence->height;
    decoder->vertical_position_extension = sequence->picture_height > 2800;
    decoder->chroma_format = (sequence->chroma_width == sequence->width) +
                             (sequence->chroma_height == sequence->height);

    if (mpeg2dec->sequence.width != (unsigned)-1)
    {
        /*
         * According to 6.1.1.6, repeat sequence headers should be
         * identical to the original. However some encoders don't
         * respect that and change various fields (including bitrate
         * and aspect ratio) in the repeat sequence headers. So we
         * choose to be as conservative as possible and only restart
         * the decoder if the width, height, chroma_width,
         * chroma_height or low_delay flag are modified.
         */
        if (sequence->width != mpeg2dec->sequence.width ||
            sequence->height != mpeg2dec->sequence.height ||
            sequence->chroma_width != mpeg2dec->sequence.chroma_width ||
            sequence->chroma_height != mpeg2dec->sequence.chroma_height ||
            ((sequence->flags ^ mpeg2dec->sequence.flags) &
             SEQ_FLAG_LOW_DELAY))
        {
            decoder->stride_frame = sequence->width;
            mpeg2_header_end (mpeg2dec);
            mpeg2dec->action = invalid_end_action;
            mpeg2dec->state = STATE_INVALID_END;
            return;
        }

        mpeg2dec->state = rb->memcmp(&mpeg2dec->sequence, sequence,
                                 sizeof (mpeg2_sequence_t)) ?
                            STATE_SEQUENCE_MODIFIED :
                            STATE_SEQUENCE_REPEATED;
    }
    else
    {
        decoder->stride_frame = sequence->width;
    }

    mpeg2dec->sequence = *sequence;
    mpeg2_reset_info(&mpeg2dec->info);
    mpeg2dec->info.sequence = &mpeg2dec->sequence;
    mpeg2dec->info.gop = NULL;

    info_user_data (mpeg2dec);
}

int mpeg2_header_gop (mpeg2dec_t * mpeg2dec)
{
    uint8_t * buffer = mpeg2dec->chunk_start;
    mpeg2_gop_t * gop = &mpeg2dec->new_gop;

    if (!(buffer[1] & 8))
        return 1;

    gop->hours = (buffer[0] >> 2) & 31;
    gop->minutes = ((buffer[0] << 4) | (buffer[1] >> 4)) & 63;
    gop->seconds = ((buffer[1] << 3) | (buffer[2] >> 5)) & 63;
    gop->pictures = ((buffer[2] << 1) | (buffer[3] >> 7)) & 63;
    gop->flags = (buffer[0] >> 7) | ((buffer[3] >> 4) & 6);

    mpeg2dec->state = STATE_GOP;
    return 0;
}

void mpeg2_header_gop_finalize (mpeg2dec_t * mpeg2dec)
{
    mpeg2dec->gop = mpeg2dec->new_gop;
    mpeg2_reset_info (&mpeg2dec->info);
    mpeg2dec->info.gop = &mpeg2dec->gop;
    info_user_data (mpeg2dec);
}

void mpeg2_set_fbuf (mpeg2dec_t * mpeg2dec, int b_type)
{
    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;
        }
    }
}

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;

    mpeg2dec->state = (mpeg2dec->state != STATE_SLICE_1ST) ?
                       STATE_PICTURE : STATE_PICTURE_2ND;
    mpeg2dec->ext_state = PIC_CODING_EXT;

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

    type = (buffer [1] >> 3) & 7;

    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;
    }

    picture->flags = PIC_FLAG_PROGRESSIVE_FRAME | type;
    picture->tag = picture->tag2 = 0;

    if (mpeg2dec->num_tags)
    {
        if (mpeg2dec->bytes_since_tag >= mpeg2dec->chunk_ptr - buffer + 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->nb_fields = 2;
    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;

    /* XXXXXX decode extra_information_picture as well */

    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;

    if (!(buffer[4] & 0x80))
        flags &= ~PIC_FLAG_PROGRESSIVE_FRAME;

    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)
{
    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)
            {
                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,
                                   mpeg2dec->convert_arg, &convert_init);

                mpeg2dec->convert_start = convert_init.start;
                mpeg2dec->decoder.convert = convert_init.copy;

                int y_size = decoder->stride_frame * mpeg2dec->sequence.height;

                mpeg2dec->yuv_buf[0][0] =
                    (uint8_t *) mpeg2_malloc(y_size, MPEG2_ALLOC_YUV);
#if MPEG2_COLOR
                int uv_size = y_size >> (2 - mpeg2dec->decoder.chroma_format);

                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);
#endif

                mpeg2dec->yuv_buf[1][0] =
                    (uint8_t *) mpeg2_malloc(y_size, MPEG2_ALLOC_YUV);
#if MPEG2_COLOR
                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);
#endif
                y_size = decoder->stride_frame * 32;

                mpeg2dec->yuv_buf[2][0] =
                    (uint8_t *) mpeg2_malloc(y_size, MPEG2_ALLOC_YUV);
#if MPEG2_COLOR
                uv_size = y_size >> (2 - mpeg2dec->decoder.chroma_format);

                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);
#endif
            }

            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);
#if MPEG2_COLOR
                    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);
#endif
                }

                mpeg2_set_fbuf (mpeg2dec, (decoder->coding_type == B_TYPE));
            }
        }
        else if (!mpeg2dec->custom_fbuf)
        {
            while (mpeg2dec->alloc_index < 3)
            {
                mpeg2_fbuf_t * fbuf;

                fbuf = &mpeg2dec->fbuf_alloc[mpeg2dec->alloc_index++].fbuf;

                fbuf->id = NULL;

                int y_size = decoder->stride_frame * mpeg2dec->sequence.height;

                fbuf->buf[0] = (uint8_t *) mpeg2_malloc (y_size,
                                                         MPEG2_ALLOC_YUV);
#if MPEG2_COLOR
                int uv_size = y_size >> (2 - decoder->chroma_format);

                fbuf->buf[1] = (uint8_t *) mpeg2_malloc (uv_size,
                                                         MPEG2_ALLOC_YUV);
                fbuf->buf[2] = (uint8_t *) mpeg2_malloc (uv_size,
                                                         MPEG2_ALLOC_YUV);
#endif
            }

            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)
{
    (void)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 (* const parser[9]) (mpeg2dec_t *) =
    {
        NULL,
        sequence_ext,
        sequence_display_ext,
        quant_matrix_ext,
        copyright_ext,
        NULL,
        NULL,
        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 const int non_linear_scale[32] =
    {
         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 STATE_INTERNAL_NORETURN;
}

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;
}