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libmpeg2.c：源码内容
							/*****************************************************************************
 * libmpeg2.c: mpeg2 video decoder module making use of libmpeg2.
 *****************************************************************************
 * Copyright (C) 1999-2001 the VideoLAN team
 * $Id: c55a243c27fb75f94936373dbf8bc773c3263cd8 $
 *
 * Authors: Gildas Bazin <gbazin@videolan.org>
 *          Christophe Massiot <massiot@via.ecp.fr>
 *
 * This program 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.
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
 *****************************************************************************/
/*****************************************************************************
 * Preamble
 *****************************************************************************/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
#include <assert.h>
#include <vlc_common.h>
#include <vlc_plugin.h>
#include <vlc_vout.h>
#include <vlc_codec.h>
#include <vlc_block_helper.h>
#include "../codec/cc.h"
#include <mpeg2.h>
#include <vlc_codec_synchro.h>
/*****************************************************************************
 * decoder_sys_t : libmpeg2 decoder descriptor
 *****************************************************************************/
#define DPB_COUNT (3+1)
typedef struct
{
    picture_t *p_picture;
    bool      b_linked;
    bool      b_displayed;
} picture_dpb_t;
struct decoder_sys_t
{
    /*
     * libmpeg2 properties
     */
    mpeg2dec_t          *p_mpeg2dec;
    const mpeg2_info_t  *p_info;
    bool                b_skip;
    /*
     * Input properties
     */
    mtime_t          i_previous_pts;
    mtime_t          i_current_pts;
    mtime_t          i_previous_dts;
    mtime_t          i_current_dts;
    bool             b_garbage_pic;
    bool             b_after_sequence_header; /* is it the next frame after
                                               * the sequence header ?    */
    bool             b_slice_i;             /* intra-slice refresh stream */
    bool             b_second_field;
    bool             b_preroll;
    /* */
    picture_dpb_t        p_dpb[DPB_COUNT];
    /*
     * Output properties
     */
    decoder_synchro_t *p_synchro;
    int             i_aspect;
    int             i_sar_num;
    int             i_sar_den;
    mtime_t         i_last_frame_pts;
    /* Closed captioning support */
    uint32_t        i_cc_flags;
    mtime_t         i_cc_pts;
    mtime_t         i_cc_dts;
    cc_data_t       cc;
    uint8_t        *p_gop_user_data;
    uint32_t        i_gop_user_data;
};
/*****************************************************************************
 * Local prototypes
 *****************************************************************************/
static int  OpenDecoder( vlc_object_t * );
static void CloseDecoder( vlc_object_t * );
static picture_t *DecodeBlock( decoder_t *, block_t ** );
static block_t   *GetCc( decoder_t *p_dec, bool pb_present[4] );
static picture_t *GetNewPicture( decoder_t * );
static void PutPicture( decoder_t *, picture_t * );
static void GetAR( decoder_t *p_dec );
static void Reset( decoder_t *p_dec );
/* */
static void DpbInit( decoder_t * );
static void DpbClean( decoder_t * );
static picture_t *DpbNewPicture( decoder_t * );
static void DpbUnlinkPicture( decoder_t *, picture_t * );
static int DpbDisplayPicture( decoder_t *, picture_t * );
/*****************************************************************************
 * Module descriptor
 *****************************************************************************/
vlc_module_begin ()
    set_description( N_("MPEG I/II video decoder (using libmpeg2)") )
    set_capability( "decoder", 150 )
    set_category( CAT_INPUT )
    set_subcategory( SUBCAT_INPUT_VCODEC )
    set_callbacks( OpenDecoder, CloseDecoder )
    add_shortcut( "libmpeg2" )
vlc_module_end ()
/*****************************************************************************
 * OpenDecoder: probe the decoder and return score
 *****************************************************************************/
static int OpenDecoder( vlc_object_t *p_this )
{
    decoder_t *p_dec = (decoder_t*)p_this;
    decoder_sys_t *p_sys;
    uint32_t i_accel = 0;
    if( p_dec->fmt_in.i_codec != VLC_FOURCC('m','p','g','v') &&
        p_dec->fmt_in.i_codec != VLC_FOURCC('m','p','g','1') &&
        /* Pinnacle hardware-mpeg1 */
        p_dec->fmt_in.i_codec != VLC_FOURCC('P','I','M','1') &&
        p_dec->fmt_in.i_codec != VLC_FOURCC('m','p','2','v') &&
        p_dec->fmt_in.i_codec != VLC_FOURCC('m','p','g','2') &&
        p_dec->fmt_in.i_codec != VLC_FOURCC('h','d','v','2') )
    {
        return VLC_EGENERIC;
    }
    /* Allocate the memory needed to store the decoder's structure */
    if( ( p_dec->p_sys = p_sys = calloc( 1, sizeof(*p_sys)) ) == NULL )
        return VLC_ENOMEM;
    /* Initialize the thread properties */
    p_sys->p_mpeg2dec = NULL;
    p_sys->p_synchro  = NULL;
    p_sys->p_info     = NULL;
    p_sys->i_current_pts  = 0;
    p_sys->i_previous_pts = 0;
    p_sys->i_current_dts  = 0;
    p_sys->i_previous_dts = 0;
    p_sys->i_aspect = 0;
    p_sys->b_garbage_pic = false;
    p_sys->b_slice_i  = false;
    p_sys->b_second_field = false;
    p_sys->b_skip     = false;
    p_sys->b_preroll = false;
    DpbInit( p_dec );
    p_sys->i_cc_pts = 0;
    p_sys->i_cc_dts = 0;
    p_sys->i_cc_flags = 0;
#if MPEG2_RELEASE >= MPEG2_VERSION (0, 5, 0)
    p_dec->pf_get_cc = GetCc;
    cc_Init( &p_sys->cc );
#endif
    p_sys->p_gop_user_data = NULL;
    p_sys->i_gop_user_data = 0;
#if defined( __i386__ ) || defined( __x86_64__ )
    if( vlc_CPU() & CPU_CAPABILITY_MMX )
    {
        i_accel |= MPEG2_ACCEL_X86_MMX;
    }
    if( vlc_CPU() & CPU_CAPABILITY_3DNOW )
    {
        i_accel |= MPEG2_ACCEL_X86_3DNOW;
    }
    if( vlc_CPU() & CPU_CAPABILITY_MMXEXT )
    {
        i_accel |= MPEG2_ACCEL_X86_MMXEXT;
    }
#elif defined( __powerpc__ ) || defined( __ppc__ ) || defined( __ppc64__ )
    if( vlc_CPU() & CPU_CAPABILITY_ALTIVEC )
    {
        i_accel |= MPEG2_ACCEL_PPC_ALTIVEC;
    }
#else
    /* If we do not know this CPU, trust libmpeg2's feature detection */
    i_accel = MPEG2_ACCEL_DETECT;
#endif
    /* Set CPU acceleration features */
    mpeg2_accel( i_accel );
    /* Initialize decoder */
    p_sys->p_mpeg2dec = mpeg2_init();
    if( p_sys->p_mpeg2dec == NULL)
    {
        msg_Err( p_dec, "mpeg2_init() failed" );
        free( p_sys );
        return VLC_EGENERIC;
    }
    p_sys->p_info = mpeg2_info( p_sys->p_mpeg2dec );
    p_dec->pf_decode_video = DecodeBlock;
    p_dec->fmt_out.i_cat = VIDEO_ES;
    p_dec->fmt_out.i_codec = 0;
    return VLC_SUCCESS;
}
/*****************************************************************************
 * RunDecoder: the libmpeg2 decoder
 *****************************************************************************/
static picture_t *DecodeBlock( decoder_t *p_dec, block_t **pp_block )
{
    decoder_sys_t   *p_sys = p_dec->p_sys;
    mpeg2_state_t   state;
    picture_t       *p_pic;
    block_t *p_block;
    if( !pp_block || !*pp_block )
        return NULL;
    p_block = *pp_block;
    if( p_block->i_flags & (BLOCK_FLAG_DISCONTINUITY | BLOCK_FLAG_CORRUPTED) )
        Reset( p_dec );
    while( 1 )
    {
        state = mpeg2_parse( p_sys->p_mpeg2dec );
        switch( state )
        {
        case STATE_SEQUENCE:
        {
            /* */
            DpbClean( p_dec );
            /* */
            mpeg2_custom_fbuf( p_sys->p_mpeg2dec, 1 );
            /* Set the first 2 reference frames */
            p_sys->i_aspect = 0;
            GetAR( p_dec );
            for( int i = 0; i < 2; i++ )
            {
                picture_t *p_picture = DpbNewPicture( p_dec );
                if( !p_picture )
                {
                    Reset( p_dec );
                    block_Release( p_block );
                    return NULL;
                }
                PutPicture( p_dec, p_picture );
            }
            if( p_sys->p_synchro )
                decoder_SynchroRelease( p_sys->p_synchro );
            if( p_sys->p_info->sequence->frame_period <= 0 )
                p_sys->p_synchro = NULL;
            else
                p_sys->p_synchro =
                decoder_SynchroInit( p_dec, (uint32_t)(UINT64_C(1001000000) *
                                27 / p_sys->p_info->sequence->frame_period) );
            p_sys->b_after_sequence_header = true;
            break;
        }
        case STATE_GOP:
            /* There can be userdata in a GOP. It needs to be remembered for the next picture. */
            if( p_sys->p_info->user_data_len > 2 )
            {
                free( p_sys->p_gop_user_data );
                p_sys->p_gop_user_data = calloc( p_sys->p_info->user_data_len, sizeof(uint8_t) );
                if( p_sys->p_gop_user_data )
                {
                    p_sys->i_gop_user_data = p_sys->p_info->user_data_len;
                    memcpy( p_sys->p_gop_user_data, p_sys->p_info->user_data, p_sys->p_info->user_data_len );
                }
            }
            break;
        case STATE_PICTURE:
        {
            const mpeg2_info_t *p_info = p_sys->p_info;
            const mpeg2_picture_t *p_current = p_info->current_picture;
            mtime_t i_pts, i_dts;
            if( p_sys->b_after_sequence_header &&
                (p_current->flags &
                    PIC_MASK_CODING_TYPE) == PIC_FLAG_CODING_TYPE_P )
            {
                /* Intra-slice refresh. Simulate a blank I picture. */
                msg_Dbg( p_dec, "intra-slice refresh stream" );
                decoder_SynchroNewPicture( p_sys->p_synchro,
                                           I_CODING_TYPE, 2, 0, 0,
                                           p_info->sequence->flags & SEQ_FLAG_LOW_DELAY );
                decoder_SynchroDecode( p_sys->p_synchro );
                decoder_SynchroEnd( p_sys->p_synchro, I_CODING_TYPE, 0 );
                p_sys->b_slice_i = true;
            }
            p_sys->b_after_sequence_header = false;
#ifdef PIC_FLAG_PTS
            i_pts = p_current->flags & PIC_FLAG_PTS ?
                ( ( p_current->pts ==
                    (uint32_t)p_sys->i_current_pts ) ?
                  p_sys->i_current_pts : p_sys->i_previous_pts ) : 0;
            i_dts = 0;
            /* Hack to handle demuxers which only have DTS timestamps */
            if( !i_pts && !p_block->i_pts && p_block->i_dts > 0 )
            {
                if( p_info->sequence->flags & SEQ_FLAG_LOW_DELAY ||
                    (p_current->flags &
                      PIC_MASK_CODING_TYPE) == PIC_FLAG_CODING_TYPE_B )
                {
                    i_pts = p_block->i_dts;
                }
            }
            p_block->i_pts = p_block->i_dts = 0;
            /* End hack */
#else /* New interface */
            i_pts = p_current->flags & PIC_FLAG_TAGS ?
                ( ( p_current->tag == (uint32_t)p_sys->i_current_pts ) ?
                            p_sys->i_current_pts : p_sys->i_previous_pts ) : 0;
            i_dts = p_current->flags & PIC_FLAG_TAGS ?
                ( ( p_current->tag2 == (uint32_t)p_sys->i_current_dts ) ?
                            p_sys->i_current_dts : p_sys->i_previous_dts ) : 0;
#endif
            /* If nb_fields == 1, it is a field picture, and it will be
             * followed by another field picture for which we won't call
             * decoder_SynchroNewPicture() because this would have other
             * problems, so we take it into account here.
             * This kind of sucks, but I didn't think better. --Meuuh
             */
            decoder_SynchroNewPicture( p_sys->p_synchro,
                                       p_current->flags & PIC_MASK_CODING_TYPE,
                                       p_current->nb_fields == 1 ? 2 :
                                       p_current->nb_fields, i_pts, i_dts,
                                       p_info->sequence->flags & SEQ_FLAG_LOW_DELAY );
            bool b_skip = false;
            if( !p_dec->b_pace_control && !p_sys->b_preroll &&
                !(p_sys->b_slice_i
                   && ((p_current->flags
                         & PIC_MASK_CODING_TYPE) == PIC_FLAG_CODING_TYPE_P))
                   && !decoder_SynchroChoose( p_sys->p_synchro,
                              p_current->flags
                                & PIC_MASK_CODING_TYPE,
                              /*p_sys->p_vout->render_time*/ 0 /*FIXME*/,
                              p_info->sequence->flags & SEQ_FLAG_LOW_DELAY ) )
            {
                b_skip = true;
            }
            p_pic = NULL;
            if( !b_skip )
            {
                p_pic = DpbNewPicture( p_dec );
                if( !p_pic )
                {
                    Reset( p_dec );
                    p_pic = DpbNewPicture( p_dec );
                    if( !p_pic )
                    {
                        mpeg2_reset( p_sys->p_mpeg2dec, 1 );
                        block_Release( p_block );
                        return NULL;
                    }
                }
            }
            if( b_skip || !p_pic )
            {
                mpeg2_skip( p_sys->p_mpeg2dec, 1 );
                p_sys->b_skip = true;
                decoder_SynchroTrash( p_sys->p_synchro );
                PutPicture( p_dec, NULL );
                if( !b_skip )
                {
                    block_Release( p_block );
                    return NULL;
                }
            }
            else
            {
                mpeg2_skip( p_sys->p_mpeg2dec, 0 );
                p_sys->b_skip = false;
                decoder_SynchroDecode( p_sys->p_synchro );
                PutPicture( p_dec, p_pic );
            }
            if( p_info->user_data_len > 2 || p_sys->i_gop_user_data > 2 )
            {
                p_sys->i_cc_pts = i_pts;
                p_sys->i_cc_dts = i_dts;
                if( (p_current->flags
                             & PIC_MASK_CODING_TYPE) == PIC_FLAG_CODING_TYPE_P )
                    p_sys->i_cc_flags = BLOCK_FLAG_TYPE_P;
                else if( (p_current->flags
                             & PIC_MASK_CODING_TYPE) == PIC_FLAG_CODING_TYPE_B )
                    p_sys->i_cc_flags = BLOCK_FLAG_TYPE_B;
                else p_sys->i_cc_flags = BLOCK_FLAG_TYPE_I;
                if( p_sys->i_gop_user_data > 2 )
                {
                    /* We now have picture info for any cached user_data out of the gop */
                    cc_Extract( &p_sys->cc, &p_sys->p_gop_user_data[0], p_sys->i_gop_user_data );
                    p_sys->i_gop_user_data = 0;
                }
                /* Extract the CC from the user_data of the picture */
                if( p_info->user_data_len > 2 )
                    cc_Extract( &p_sys->cc, &p_info->user_data[0], p_info->user_data_len );
            }
        }
        break;
        case STATE_BUFFER:
            if( !p_block->i_buffer )
            {
                block_Release( p_block );
                return NULL;
            }
            if( (p_block->i_flags & (BLOCK_FLAG_DISCONTINUITY
                                      | BLOCK_FLAG_CORRUPTED)) &&
                p_sys->p_synchro &&
                p_sys->p_info->sequence &&
                p_sys->p_info->sequence->width != (unsigned)-1 )
            {
                decoder_SynchroReset( p_sys->p_synchro );
                if( p_sys->p_info->current_fbuf != NULL &&
                    p_sys->p_info->current_fbuf->id != NULL )
                {
                    p_sys->b_garbage_pic = true;
                }
                if( p_sys->b_slice_i )
                {
                    decoder_SynchroNewPicture( p_sys->p_synchro,
                                               I_CODING_TYPE, 2, 0, 0,
                                               p_sys->p_info->sequence->flags &
                                                            SEQ_FLAG_LOW_DELAY );
                    decoder_SynchroDecode( p_sys->p_synchro );
                    decoder_SynchroEnd( p_sys->p_synchro, I_CODING_TYPE, 0 );
                }
            }
            if( p_block->i_flags & BLOCK_FLAG_PREROLL )
            {
                p_sys->b_preroll = true;
            }
            else if( p_sys->b_preroll )
            {
                p_sys->b_preroll = false;
                if( p_sys->p_synchro )
                    decoder_SynchroReset( p_sys->p_synchro );
            }
#ifdef PIC_FLAG_PTS
            if( p_block->i_pts )
            {
                mpeg2_pts( p_sys->p_mpeg2dec, (uint32_t)p_block->i_pts );
#else /* New interface */
            if( p_block->i_pts || p_block->i_dts )
            {
                mpeg2_tag_picture( p_sys->p_mpeg2dec,
                                   (uint32_t)p_block->i_pts,
                                   (uint32_t)p_block->i_dts );
#endif
                p_sys->i_previous_pts = p_sys->i_current_pts;
                p_sys->i_current_pts = p_block->i_pts;
                p_sys->i_previous_dts = p_sys->i_current_dts;
                p_sys->i_current_dts = p_block->i_dts;
            }
            mpeg2_buffer( p_sys->p_mpeg2dec, p_block->p_buffer,
                          p_block->p_buffer + p_block->i_buffer );
            p_block->i_buffer = 0;
            break;
#if MPEG2_RELEASE >= MPEG2_VERSION (0, 5, 0)
        case STATE_SEQUENCE_MODIFIED:
            GetAR( p_dec );
            break;
#endif
        case STATE_PICTURE_2ND:
            p_sys->b_second_field = true;
            break;
        case STATE_INVALID_END:
        case STATE_END:
        case STATE_SLICE:
            p_pic = NULL;
            if( p_sys->p_info->display_fbuf &&
                p_sys->p_info->display_fbuf->id )
            {
                p_pic = p_sys->p_info->display_fbuf->id;
                if( DpbDisplayPicture( p_dec, p_pic ) )
                    p_pic = NULL;
                decoder_SynchroEnd( p_sys->p_synchro,
                                    p_sys->p_info->display_picture->flags & PIC_MASK_CODING_TYPE,
                                    p_sys->b_garbage_pic );
                if( p_pic )
                {
                    p_pic->date = decoder_SynchroDate( p_sys->p_synchro );
                    if( p_sys->b_garbage_pic )
                        p_pic->date = 0; /* ??? */
                    p_sys->b_garbage_pic = false;
                }
            }
            if( p_sys->p_info->discard_fbuf &&
                p_sys->p_info->discard_fbuf->id )
            {
                DpbUnlinkPicture( p_dec, p_sys->p_info->discard_fbuf->id );
            }
            /* For still frames */
            if( state == STATE_END && p_pic )
                p_pic->b_force = true;
            if( p_pic )
            {
                /* Avoid frames with identical timestamps.
                 * Especially needed for still frames in DVD menus. */
                if( p_sys->i_last_frame_pts == p_pic->date )
                    p_pic->date++;
                p_sys->i_last_frame_pts = p_pic->date;
                return p_pic;
            }
            break;
        case STATE_INVALID:
        {
            msg_Err( p_dec, "invalid picture encountered" );
            /* I don't think we have anything to do, but well without
             * docs ... */
            break;
        }
        default:
            break;
        }
    }
    /* Never reached */
    return NULL;
}
/*****************************************************************************
 * CloseDecoder: libmpeg2 decoder destruction
 *****************************************************************************/
static void CloseDecoder( vlc_object_t *p_this )
{
    decoder_t *p_dec = (decoder_t *)p_this;
    decoder_sys_t *p_sys = p_dec->p_sys;
    DpbClean( p_dec );
    free( p_sys->p_gop_user_data );
    if( p_sys->p_synchro ) decoder_SynchroRelease( p_sys->p_synchro );
    if( p_sys->p_mpeg2dec ) mpeg2_close( p_sys->p_mpeg2dec );
    free( p_sys );
}
/*****************************************************************************
 * Reset: reset the decoder state
 *****************************************************************************/
static void Reset( decoder_t *p_dec )
{
    decoder_sys_t *p_sys = p_dec->p_sys;
    cc_Flush( &p_sys->cc );
    mpeg2_reset( p_sys->p_mpeg2dec, 0 );
    DpbClean( p_dec );
}
/*****************************************************************************
 * GetNewPicture: Get a new picture from the vout and set the buf struct
 *****************************************************************************/
static picture_t *GetNewPicture( decoder_t *p_dec )
{
    decoder_sys_t *p_sys = p_dec->p_sys;
    picture_t *p_pic;
    p_dec->fmt_out.video.i_width = p_sys->p_info->sequence->width;
    p_dec->fmt_out.video.i_visible_width =
        p_sys->p_info->sequence->picture_width;
    p_dec->fmt_out.video.i_height = p_sys->p_info->sequence->height;
    p_dec->fmt_out.video.i_visible_height =
        p_sys->p_info->sequence->picture_height;
    p_dec->fmt_out.video.i_aspect = p_sys->i_aspect;
    p_dec->fmt_out.video.i_sar_num = p_sys->i_sar_num;
    p_dec->fmt_out.video.i_sar_den = p_sys->i_sar_den;
    if( p_sys->p_info->sequence->frame_period > 0 )
    {
        p_dec->fmt_out.video.i_frame_rate =
            (uint32_t)( (uint64_t)1001000000 * 27 /
                        p_sys->p_info->sequence->frame_period );
        p_dec->fmt_out.video.i_frame_rate_base = 1001;
    }
    p_dec->fmt_out.i_codec =
        ( p_sys->p_info->sequence->chroma_height <
          p_sys->p_info->sequence->height ) ?
        VLC_FOURCC('I','4','2','0') : VLC_FOURCC('I','4','2','2');
    /* Get a new picture */
    p_pic = decoder_NewPicture( p_dec );
    if( p_pic == NULL )
        return NULL;
    p_pic->b_progressive = p_sys->p_info->current_picture != NULL ?
        p_sys->p_info->current_picture->flags & PIC_FLAG_PROGRESSIVE_FRAME : 1;
    p_pic->b_top_field_first = p_sys->p_info->current_picture != NULL ?
        p_sys->p_info->current_picture->flags & PIC_FLAG_TOP_FIELD_FIRST : 1;
    p_pic->i_nb_fields = p_sys->p_info->current_picture != NULL ?
        p_sys->p_info->current_picture->nb_fields : 2;
    return p_pic;
}
/*****************************************************************************
 * GetCc: Retrieves the Closed Captions for the CC decoder.
 *****************************************************************************/
static block_t *GetCc( decoder_t *p_dec, bool pb_present[4] )
{
    decoder_sys_t   *p_sys = p_dec->p_sys;
    block_t         *p_cc = NULL;
    int i;
    for( i = 0; i < 4; i++ )
        pb_present[i] = p_sys->cc.pb_present[i];
    if( p_sys->cc.i_data <= 0 )
        return NULL;
    p_cc = block_New( p_dec, p_sys->cc.i_data);
    if( p_cc )
    {
        memcpy( p_cc->p_buffer, p_sys->cc.p_data, p_sys->cc.i_data );
        p_cc->i_dts =
        p_cc->i_pts = p_sys->cc.b_reorder ? p_sys->i_cc_pts : p_sys->i_cc_dts;
        p_cc->i_flags = ( p_sys->cc.b_reorder  ? p_sys->i_cc_flags : BLOCK_FLAG_TYPE_P ) & ( BLOCK_FLAG_TYPE_I|BLOCK_FLAG_TYPE_P|BLOCK_FLAG_TYPE_B);
    }
    cc_Flush( &p_sys->cc );
    return p_cc;
}
/*****************************************************************************
 * GetAR: Get aspect ratio
 *****************************************************************************/
static void GetAR( decoder_t *p_dec )
{
    decoder_sys_t *p_sys = p_dec->p_sys;
    int i_old_aspect = p_sys->i_aspect;
    /* Check whether the input gave a particular aspect ratio */
    if( p_dec->fmt_in.video.i_aspect )
    {
        p_sys->i_aspect = p_dec->fmt_in.video.i_aspect;
    }
    else
    {
        /* Use the value provided in the MPEG sequence header */
        if( p_sys->p_info->sequence->pixel_height > 0 )
        {
            p_sys->i_aspect =
                ((uint64_t)p_sys->p_info->sequence->picture_width) *
                p_sys->p_info->sequence->pixel_width *
                VOUT_ASPECT_FACTOR /
                p_sys->p_info->sequence->picture_height /
                p_sys->p_info->sequence->pixel_height;
            p_sys->i_sar_num = p_sys->p_info->sequence->pixel_width;
            p_sys->i_sar_den = p_sys->p_info->sequence->pixel_height;
        }
        else
        {
            /* Invalid aspect, assume 4:3.
             * This shouldn't happen and if it does it is a bug
             * in libmpeg2 (likely triggered by an invalid stream) */
            p_sys->i_aspect = VOUT_ASPECT_FACTOR * 4 / 3;
            p_sys->i_sar_num = p_sys->p_info->sequence->picture_height * 4;
            p_sys->i_sar_den = p_sys->p_info->sequence->picture_width * 3;
        }
    }
    if( p_sys->i_aspect == i_old_aspect )
        return;
    if( p_sys->p_info->sequence->frame_period > 0 )
        msg_Dbg( p_dec,
                 "%dx%d (display %d,%d), aspect %d, sar %i:%i, %u.%03u fps",
                 p_sys->p_info->sequence->picture_width,
                 p_sys->p_info->sequence->picture_height,
                 p_sys->p_info->sequence->display_width,
                 p_sys->p_info->sequence->display_height,
                 p_sys->i_aspect, p_sys->i_sar_num, p_sys->i_sar_den,
                 (uint32_t)((uint64_t)1001000000 * 27 /
                     p_sys->p_info->sequence->frame_period / 1001),
                 (uint32_t)((uint64_t)1001000000 * 27 /
                     p_sys->p_info->sequence->frame_period % 1001) );
    else
        msg_Dbg( p_dec, "bad frame period" );
}
/*****************************************************************************
 * PutPicture: Put a picture_t in mpeg2 context
 *****************************************************************************/
static void PutPicture( decoder_t *p_dec, picture_t *p_picture )
{
    decoder_sys_t *p_sys = p_dec->p_sys;
    /* */
    uint8_t *pp_buf[3];
    for( int j = 0; j < 3; j++ )
        pp_buf[j] = p_picture ? p_picture->p[j].p_pixels : NULL;
    mpeg2_set_buf( p_sys->p_mpeg2dec, pp_buf, p_picture );
    /* Completly broken API, why the hell does it suppose
     * the stride of the chroma planes ! */
    if( p_picture )
        mpeg2_stride( p_sys->p_mpeg2dec, p_picture->p[Y_PLANE].i_pitch );
}
/**
 * Initialize a virtual Decoded Picture Buffer to workaround
 * libmpeg2 deficient API
 */
static void DpbInit( decoder_t *p_dec )
{
    decoder_sys_t *p_sys = p_dec->p_sys;
    for( int i = 0; i < DPB_COUNT; i++ )
        p_sys->p_dpb[i].p_picture = NULL;
}
/**
 * Empty and reset the current DPB
 */
static void DpbClean( decoder_t *p_dec )
{
    decoder_sys_t *p_sys = p_dec->p_sys;
    for( int i = 0; i < DPB_COUNT; i++ )
    {
        picture_dpb_t *p = &p_sys->p_dpb[i];
        if( !p->p_picture )
            continue;
        if( p->b_linked )
            decoder_UnlinkPicture( p_dec, p->p_picture );
        if( !p->b_displayed )
            decoder_DeletePicture( p_dec, p->p_picture );
        p->p_picture = NULL;
    }
}
/**
 * Retreive a picture and reserve a place in the DPB
 */
static picture_t *DpbNewPicture( decoder_t *p_dec )
{
    decoder_sys_t *p_sys = p_dec->p_sys;
    picture_dpb_t *p;
    int i;
    for( i = 0; i < DPB_COUNT; i++ )
    {
        p = &p_sys->p_dpb[i];
        if( !p->p_picture )
            break;
    }
    if( i >= DPB_COUNT )
    {
        msg_Err( p_dec, "Leaking picture" );
        return NULL;
    }
    p->p_picture = GetNewPicture( p_dec );
    if( p->p_picture )
    {
        decoder_LinkPicture( p_dec, p->p_picture );
        p->b_linked = true;
        p->b_displayed = false;
        p->p_picture->date = 0;
    }
    return p->p_picture;
}
static picture_dpb_t *DpbFindPicture( decoder_t *p_dec, picture_t *p_picture )
{
    decoder_sys_t *p_sys = p_dec->p_sys;
    for( int i = 0; i < DPB_COUNT; i++ )
    {
        picture_dpb_t *p = &p_sys->p_dpb[i];
        if( p->p_picture == p_picture )
            return p;
    }
    return NULL;
}
/**
 * Unlink the provided picture and ensure that the decoder
 * does not own it anymore.
 */
static void DpbUnlinkPicture( decoder_t *p_dec, picture_t *p_picture )
{
    picture_dpb_t *p = DpbFindPicture( p_dec, p_picture );
    /* XXX it is needed to workaround libmpeg2 bugs */
    if( !p || !p->b_linked )
    {
        msg_Err( p_dec, "DpbUnlinkPicture called on an invalid picture" );
        return;
    }
    assert( p && p->b_linked );
    decoder_UnlinkPicture( p_dec, p->p_picture );
    p->b_linked = false;
    if( !p->b_displayed )
        decoder_DeletePicture( p_dec, p->p_picture );
    p->p_picture = NULL;
}
/**
 * Mark the provided picture as displayed.
 */
static int DpbDisplayPicture( decoder_t *p_dec, picture_t *p_picture )
{
    picture_dpb_t *p = DpbFindPicture( p_dec, p_picture );
    /* XXX it is needed to workaround libmpeg2 bugs */
    if( !p || p->b_displayed || !p->b_linked )
    {
        msg_Err( p_dec, "DpbDisplayPicture called on an invalid picture" );
        return VLC_EGENERIC;
    }
    assert( p && !p->b_displayed && p->b_linked );
    p->b_displayed = true;
    return VLC_SUCCESS;
}

						