Quelle  image.c   Sprache: C

/*****************************************************************************
 * image.c : wrapper for image reading/writing facilities
 *****************************************************************************
 * Copyright (C) 2004-2007 VLC authors and VideoLAN
 *
 * Author: Gildas Bazin <gbazin@videolan.org>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser 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.
 *****************************************************************************/

/**
 * \file
 * This file contains the functions to handle the image_handler_t type
 */

/*****************************************************************************
 * Preamble
 *****************************************************************************/

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <errno.h>
#include <limits.h>

#include <vlc_common.h>
#include <vlc_codec.h>
#include <vlc_meta.h>
#include <vlc_filter.h>
#include <vlc_es.h>
#include <vlc_image.h>
#include <vlc_stream.h>
#include <vlc_fs.h>
#include <vlc_sout.h>
#include "../libvlc.h"
#include <vlc_modules.h>

struct decoder_owner
{
    decoder_t dec;
    es_format_t fmt_in;
    image_handler_t *p_image;
};

static inline struct decoder_owner *dec_get_owner( decoder_t *p_dec )
{
    return container_of( p_dec, struct decoder_owner, dec );
}

static picture_t *ImageRead( image_handler_t *, block_t *,
                             const es_format_t *,
                             video_format_t * );
static picture_t *ImageReadUrl( image_handler_t *, const char *,
                                video_format_t * );
static block_t *ImageWrite( image_handler_t *, picture_t *,
                            const video_format_t *,
                            vlc_fourcc_t, const video_format_t * );
static int ImageWriteUrl( image_handler_t *, picture_t *,
                          const video_format_t *,
                          vlc_fourcc_t, const video_format_t *,
                          const char * );

static picture_t *ImageConvert( image_handler_t *, picture_t *,
                                const video_format_t *, video_format_t * );

static decoder_t *CreateDecoder( image_handler_t *, const es_format_t * );
static encoder_t *CreateEncoder( vlc_object_t *, const video_format_t *,
                                 vlc_fourcc_t, const video_format_t * );
static filter_t *CreateConverter( vlc_object_t *, const es_format_t *,
                                  struct vlc_video_context *,
                                  const video_format_t * );
static void DeleteConverter( filter_t * );

vlc_fourcc_t image_Type2Fourcc( const char * );
vlc_fourcc_t image_Ext2Fourcc( const char * );
/*static const char *Fourcc2Ext( vlc_fourcc_t );*/

#undef image_HandlerCreate
/**
 * Create an image_handler_t instance
 *
 */
image_handler_t *image_HandlerCreate( vlc_object_t *p_this )
{
    image_handler_t *p_image = calloc( 1, sizeof(image_handler_t) );
    if( !p_image )
        return NULL;

    p_image->p_parent = p_this;

    p_image->pf_read = ImageRead;
    p_image->pf_read_url = ImageReadUrl;
    p_image->pf_write = ImageWrite;
    p_image->pf_write_url = ImageWriteUrl;
    p_image->pf_convert = ImageConvert;

    p_image->outfifo = picture_fifo_New();

    return p_image;
}

/**
 * Delete the image_handler_t instance
 *
 */
void image_HandlerDelete( image_handler_t *p_image )
{
    if( !p_image ) return;

    if( p_image->p_dec != NULL )
    {
        struct decoder_owner *p_owner = dec_get_owner( p_image->p_dec );
        decoder_Clean( p_image->p_dec );
        es_format_Clean( &p_owner->fmt_in );
        vlc_object_delete( p_image->p_dec );
    }
    if( p_image->p_enc )
        vlc_encoder_Destroy( p_image->p_enc );
    if( p_image->p_converter ) DeleteConverter( p_image->p_converter );

    picture_fifo_Delete( p_image->outfifo );

    free( p_image );
    p_image = NULL;
}

/**
 * Read an image
 *
 */

static void ImageQueueVideo( decoder_t *p_dec, picture_t *p_pic )
{
    struct decoder_owner *p_owner = dec_get_owner( p_dec );
    picture_fifo_Lock( p_owner->p_image->outfifo );
    picture_fifo_Push( p_owner->p_image->outfifo, p_pic );
    picture_fifo_Unlock( p_owner->p_image->outfifo );
}

static picture_t *ImageRead( image_handler_t *p_image, block_t *p_block,
                             const es_format_t *p_es_in,
                             video_format_t *p_fmt_out )
{
    picture_t *p_pic = NULL;

    if ( p_es_in->i_cat != VIDEO_ES )
    {
        block_Release(p_block);
        return NULL;
    }

    /* Check if we can reuse the current decoder */
    if( p_image->p_dec &&
        p_image->p_dec->fmt_in->i_codec != p_es_in->video.i_chroma )
    {
        struct decoder_owner *p_owner = dec_get_owner( p_image->p_dec );
        decoder_Clean( p_image->p_dec );
        es_format_Clean( &p_owner->fmt_in );
        vlc_object_delete( p_image->p_dec );
        p_image->p_dec = NULL;
    }

    /* Start a decoder */
    if( !p_image->p_dec )
    {
        p_image->p_dec = CreateDecoder( p_image, p_es_in );
        if( !p_image->p_dec )
        {
            block_Release(p_block);
            return NULL;
        }
        if( p_image->p_dec->fmt_out.i_cat != VIDEO_ES )
        {
            struct decoder_owner *p_owner = dec_get_owner( p_image->p_dec );
            decoder_Clean( p_image->p_dec );
            es_format_Clean( &p_owner->fmt_in );
            vlc_object_delete( p_image->p_dec );
            p_image->p_dec = NULL;
            block_Release(p_block);
            return NULL;
        }
    }

    p_block->i_pts = p_block->i_dts = vlc_tick_now();
    int ret = p_image->p_dec->pf_decode( p_image->p_dec, p_block );
    if( ret == VLCDEC_SUCCESS )
    {
        /* Drain */
        p_image->p_dec->pf_decode( p_image->p_dec, NULL );

        picture_fifo_Lock( p_image->outfifo );
        p_pic = picture_fifo_Pop( p_image->outfifo );

        unsigned lostcount = 0;
        picture_t *lostpic;
        while( ( lostpic = picture_fifo_Pop( p_image->outfifo ) ) != NULL )
        {
            picture_Release( lostpic );
            lostcount++;
        }
        picture_fifo_Unlock( p_image->outfifo );

        if( lostcount > 0 )
            msg_Warn( p_image->p_parent, "Image decoder output more than one "
                      "picture (%u)", lostcount );
    }

    if( p_pic == NULL )
    {
        msg_Warn( p_image->p_parent, "no image decoded" );
        return 0;
    }

    if( !p_fmt_out->i_chroma )
        p_fmt_out->i_chroma = p_image->p_dec->fmt_out.video.i_chroma;
    if( !p_fmt_out->i_width && p_fmt_out->i_height )
        p_fmt_out->i_width = (int64_t)p_image->p_dec->fmt_out.video.i_width *
                             p_image->p_dec->fmt_out.video.i_sar_num *
                             p_fmt_out->i_height /
                             p_image->p_dec->fmt_out.video.i_height /
                             p_image->p_dec->fmt_out.video.i_sar_den;

    if( !p_fmt_out->i_height && p_fmt_out->i_width )
        p_fmt_out->i_height = (int64_t)p_image->p_dec->fmt_out.video.i_height *
                              p_image->p_dec->fmt_out.video.i_sar_den *
                              p_fmt_out->i_width /
                              p_image->p_dec->fmt_out.video.i_width /
                              p_image->p_dec->fmt_out.video.i_sar_num;
    if( !p_fmt_out->i_width )
        p_fmt_out->i_width = p_image->p_dec->fmt_out.video.i_width;
    if( !p_fmt_out->i_height )
        p_fmt_out->i_height = p_image->p_dec->fmt_out.video.i_height;
    if( !p_fmt_out->i_visible_width )
        p_fmt_out->i_visible_width = p_fmt_out->i_width;
    if( !p_fmt_out->i_visible_height )
        p_fmt_out->i_visible_height = p_fmt_out->i_height;
    if( p_fmt_out->transfer == TRANSFER_FUNC_UNDEF )
        p_fmt_out->transfer = p_image->p_dec->fmt_out.video.transfer;
    if( p_fmt_out->primaries == COLOR_PRIMARIES_UNDEF )
        p_fmt_out->primaries = p_image->p_dec->fmt_out.video.primaries;
    if( p_fmt_out->space == COLOR_SPACE_UNDEF )
        p_fmt_out->space = p_image->p_dec->fmt_out.video.space;

    /* Check if we need chroma conversion or resizing */
    if( !video_format_IsSameChroma( &p_image->p_dec->fmt_out.video, p_fmt_out ) ||
        p_image->p_dec->fmt_out.video.i_width != p_fmt_out->i_width ||
        p_image->p_dec->fmt_out.video.i_height != p_fmt_out->i_height )
    {
        if( p_image->p_converter &&
            ( !video_format_IsSameChroma( &p_image->p_converter->fmt_in.video,
                                          &p_image->p_dec->fmt_out.video ) ||
              !video_format_IsSameChroma( &p_image->p_converter->fmt_out.video, p_fmt_out ) ) )
        {
            /* We need to restart a new filter */
            DeleteConverter( p_image->p_converter );
            p_image->p_converter = NULL;
        }

        /* Start a filter */
        if( !p_image->p_converter )
        {
            p_image->p_converter =
                CreateConverter( p_image->p_parent, &p_image->p_dec->fmt_out,
                                 picture_GetVideoContext(p_pic), p_fmt_out );

            if( !p_image->p_converter )
            {
                picture_Release( p_pic );
                return NULL;
            }
        }
        else
        {
            /* Filters should handle on-the-fly size changes */
            es_format_Clean( &p_image->p_converter->fmt_in );
            es_format_Copy( &p_image->p_converter->fmt_in, &p_image->p_dec->fmt_out );
            video_format_Clean( &p_image->p_converter->fmt_out.video );
            video_format_Copy( &p_image->p_converter->fmt_out.video, p_fmt_out);
        }

        p_pic = p_image->p_converter->ops->filter_video( p_image->p_converter, p_pic );
        assert(p_pic == NULL || !picture_HasChainedPics(p_pic)); // no chaining
    }
    else
    {
        video_format_Clean( p_fmt_out );
        video_format_Copy( p_fmt_out, &p_image->p_dec->fmt_out.video );
    }

    return p_pic;
}

static picture_t *ImageReadUrl( image_handler_t *p_image, const char *psz_url,
                                video_format_t *p_fmt_out )
{
    block_t *p_block;
    picture_t *p_pic;
    stream_t *p_stream = NULL;
    uint64_t i_size;

    p_stream = vlc_stream_NewURL( p_image->p_parent, psz_url );

    if( !p_stream )
    {
        msg_Dbg( p_image->p_parent, "could not open %s for reading",
                 psz_url );
        return NULL;
    }

    if( vlc_stream_GetSize( p_stream, &i_size ) || i_size > SSIZE_MAX )
    {
        msg_Dbg( p_image->p_parent, "could not read %s", psz_url );
        goto error;
    }

    p_block = vlc_stream_Block( p_stream, i_size );
    if( p_block == NULL )
        goto error;

    vlc_fourcc_t i_chroma = 0;
    char *psz_mime = stream_MimeType( p_stream );
    if( psz_mime != NULL )
    {
        i_chroma = image_Mime2Fourcc( psz_mime );
        free( psz_mime );
    }
    if( !i_chroma )
    {
       /* Try to guess format from file name */
       i_chroma = image_Ext2Fourcc( psz_url );
    }
    vlc_stream_Delete( p_stream );


    es_format_t fmtin;
    es_format_Init( &fmtin, VIDEO_ES, i_chroma );
    p_pic = ImageRead( p_image, p_block, &fmtin, p_fmt_out );

    es_format_Clean( &fmtin );

    return p_pic;
error:
    vlc_stream_Delete( p_stream );
    return NULL;
}

/**
 * Write an image
 *
 */

static block_t *ImageWrite( image_handler_t *p_image, picture_t *p_pic,
                            const video_format_t *p_fmt_in,
                            vlc_fourcc_t codec, const video_format_t *p_fmt_out )
{
    /* Check if we can reuse the current encoder */
    if( p_image->p_enc &&
        ( p_image->p_enc->fmt_out.i_codec != codec ||
          p_image->p_enc->fmt_out.video.i_width != p_fmt_out->i_width ||
          p_image->p_enc->fmt_out.video.i_height != p_fmt_out->i_height ) )
    {
        vlc_encoder_Destroy( p_image->p_enc );
        p_image->p_enc = 0;
    }

    /* Start an encoder */
    if( !p_image->p_enc )
    {
        p_image->p_enc = CreateEncoder( p_image->p_parent,
                                        p_fmt_in, codec, p_fmt_out );
        if( !p_image->p_enc ) return NULL;
    }

    /* We'll release the picture at the end or during conversion. */
    picture_Hold(p_pic);

    /* Check if we need chroma conversion or resizing */
    if( !video_format_IsSameChroma(&p_image->p_enc->fmt_in.video, p_fmt_in) ||
        p_image->p_enc->fmt_in.video.i_width != p_fmt_in->i_width ||
        p_image->p_enc->fmt_in.video.i_height != p_fmt_in->i_height )
    {

        if( p_image->p_converter &&
            ( !video_format_IsSameChroma( &p_image->p_converter->fmt_in.video, p_fmt_in ) ||
              !video_format_IsSameChroma( &p_image->p_converter->fmt_out.video,
                                          &p_image->p_enc->fmt_in.video ) ) )
        {
            /* We need to restart a new filter */
            DeleteConverter( p_image->p_converter );
            p_image->p_converter = NULL;
        }

        /* Start a filter */
        if( !p_image->p_converter )
        {
            es_format_t fmt_in;
            es_format_Init( &fmt_in, VIDEO_ES, p_fmt_in->i_chroma );
            fmt_in.video = *p_fmt_in;

            p_image->p_converter =
                CreateConverter( p_image->p_parent, &fmt_in,
                                 picture_GetVideoContext(p_pic), &p_image->p_enc->fmt_in.video );

            if( !p_image->p_converter )
            {
                picture_Release(p_pic);
                return NULL;
            }
        }
        else
        {
            /* Filters should handle on-the-fly size changes */
            es_format_Clean( &p_image->p_converter->fmt_in );
            es_format_InitFromVideo( &p_image->p_converter->fmt_in, p_fmt_in );
            es_format_Clean( &p_image->p_converter->fmt_out );
            es_format_Copy( &p_image->p_converter->fmt_out, &p_image->p_enc->fmt_in );
        }

        /* Hold the picture there to let the caller release its own picture,
         * since filters will consume the picture. */
        p_pic = p_image->p_converter->ops->filter_video( p_image->p_converter, p_pic );
        assert(p_pic == NULL || !picture_HasChainedPics(p_pic)); // no chaining
    }

    block_t *p_block = NULL;
    if (p_pic != NULL)
    {
        p_block = vlc_encoder_EncodeVideo(p_image->p_enc, p_pic);
        picture_Release(p_pic);
    }

    if( !p_block )
    {
        msg_Dbg( p_image->p_parent, "no image encoded" );
        return 0;
    }

    return p_block;
}

static int ImageWriteUrl( image_handler_t *p_image, picture_t *p_pic,
                          const video_format_t *p_fmt_in,
                          vlc_fourcc_t codec, const video_format_t *p_fmt_out,
                          const char *psz_url )
{
    block_t *p_block;
    FILE *file;
    video_format_t fmt_out = *p_fmt_out;

    if( !codec )
    {
        /* Try to guess format from file name */
        codec = image_Ext2Fourcc( psz_url );
    }

    file = vlc_fopen( psz_url, "wb" );
    if( !file )
    {
        msg_Err( p_image->p_parent, "%s: %s", psz_url, vlc_strerror_c(errno) );
        return VLC_EGENERIC;
    }

    p_block = ImageWrite( p_image, p_pic, p_fmt_in, codec, &fmt_out );

    int err = 0;
    if( p_block )
    {
        if( fwrite( p_block->p_buffer, p_block->i_buffer, 1, file ) != 1 )
            err = errno;
        block_Release( p_block );
    }

    if( fclose( file ) && !err )
        err = errno;

    if( err )
    {
       errno = err;
       msg_Err( p_image->p_parent, "%s: %s", psz_url, vlc_strerror_c(errno) );
    }

    return err ? VLC_EGENERIC : VLC_SUCCESS;
}

/**
 * Convert an image to a different format
 *
 */

static picture_t *ImageConvert( image_handler_t *p_image, picture_t *p_pic,
                                const video_format_t *p_fmt_in,
                                video_format_t *p_fmt_out )
{
    if( !p_fmt_out->i_width && !p_fmt_out->i_height &&
        p_fmt_out->i_sar_num && p_fmt_out->i_sar_den &&
        p_fmt_out->i_sar_num * p_fmt_in->i_sar_den !=
        p_fmt_out->i_sar_den * p_fmt_in->i_sar_num )
    {
        p_fmt_out->i_width =
            p_fmt_in->i_sar_num * (int64_t)p_fmt_out->i_sar_den *
            p_fmt_in->i_width / p_fmt_in->i_sar_den / p_fmt_out->i_sar_num;
        p_fmt_out->i_visible_width =
            p_fmt_in->i_sar_num * (int64_t)p_fmt_out->i_sar_den *
            p_fmt_in->i_visible_width / p_fmt_in->i_sar_den /
            p_fmt_out->i_sar_num;
    }

    if( !p_fmt_out->i_chroma ) p_fmt_out->i_chroma = p_fmt_in->i_chroma;
    if( !p_fmt_out->i_width )
        p_fmt_out->i_width = p_fmt_out->i_visible_width = p_fmt_in->i_width;
    if( !p_fmt_out->i_height )
        p_fmt_out->i_height = p_fmt_out->i_visible_height = p_fmt_in->i_height;
    if( !p_fmt_out->i_sar_num ) p_fmt_out->i_sar_num = p_fmt_in->i_sar_num;
    if( !p_fmt_out->i_sar_den ) p_fmt_out->i_sar_den = p_fmt_in->i_sar_den;

    if( p_image->p_converter &&
        ( !video_format_IsSameChroma( &p_image->p_converter->fmt_in.video, p_fmt_in ) ||
          !video_format_IsSameChroma( &p_image->p_converter->fmt_out.video, p_fmt_out ) ) )
    {
        /* We need to restart a new filter */
        DeleteConverter( p_image->p_converter );
        p_image->p_converter = NULL;
    }

    /* Start a filter */
    if( !p_image->p_converter )
    {
        es_format_t fmt_in;
        es_format_Init( &fmt_in, VIDEO_ES, p_fmt_in->i_chroma );
        fmt_in.video = *p_fmt_in;

        p_image->p_converter =
            CreateConverter( p_image->p_parent, &fmt_in,
                             picture_GetVideoContext(p_pic), p_fmt_out );

        if( !p_image->p_converter )
        {
            return NULL;
        }
    }
    else
    {
        /* Filters should handle on-the-fly size changes */
        es_format_Clean( &p_image->p_converter->fmt_in );
        es_format_InitFromVideo( &p_image->p_converter->fmt_in, p_fmt_in );
        es_format_Clean( &p_image->p_converter->fmt_out );
        es_format_InitFromVideo( &p_image->p_converter->fmt_out, p_fmt_out );
    }

    picture_Hold( p_pic );

    p_pic = p_image->p_converter->ops->filter_video( p_image->p_converter, p_pic );
    assert(p_pic == NULL || !picture_HasChainedPics(p_pic)); // no chaining
    return p_pic;
}

/**
 * Misc functions
 *
 */
static const struct
{
    vlc_fourcc_t i_codec;
    const char psz_ext[7];

} ext_table[] =
{
    { VLC_CODEC_JPEG,              "jpeg" },
    { VLC_CODEC_JPEG,              "jpg"  },
    { VLC_CODEC_JPEGLS,            "ljpg" },
    { VLC_CODEC_BPG,               "bpg" },
    { VLC_CODEC_PNG,               "png" },
    { VLC_CODEC_PGM,               "pgm" },
    { VLC_CODEC_PGMYUV,            "pgmyuv" },
    { VLC_FOURCC('p','b','m',' '), "pbm" },
    { VLC_FOURCC('p','a','m',' '), "pam" },
    { VLC_CODEC_TARGA,             "tga" },
    { VLC_CODEC_BMP,               "bmp" },
    { VLC_CODEC_FARBFELD,          "farb" },
    { VLC_CODEC_PNM,               "pnm" },
    { VLC_FOURCC('x','p','m',' '), "xpm" },
    { VLC_FOURCC('x','c','f',' '), "xcf" },
    { VLC_CODEC_PCX,               "pcx" },
    { VLC_CODEC_GIF,               "gif" },
    { VLC_CODEC_QOI,               "qoi" },
    { VLC_CODEC_SVG,               "svg" },
    { VLC_CODEC_TIFF,              "tif" },
    { VLC_CODEC_TIFF,              "tiff" },
    { VLC_CODEC_WEBP,              "webp" },
    { VLC_FOURCC('l','b','m',' '), "lbm" },
    { VLC_CODEC_PPM,               "ppm" },
};

vlc_fourcc_t image_Type2Fourcc( const char *psz_type )
{
    for( unsigned i = 0; i < ARRAY_SIZE(ext_table); i++ )
        if( !strcasecmp( ext_table[i].psz_ext, psz_type ) )
            return ext_table[i].i_codec;

    return 0;
}

vlc_fourcc_t image_Ext2Fourcc( const char *psz_name )
{
    psz_name = strrchr( psz_name, '.' );
    if( !psz_name ) return 0;
    psz_name++;

    return image_Type2Fourcc( psz_name );
}

static const struct
{
    vlc_fourcc_t i_codec;
    const char *psz_mime;
} mime_table[] =
{
    { VLC_CODEC_BMP,               "image/bmp" },
    { VLC_CODEC_BMP,               "image/x-bmp" },
    { VLC_CODEC_BMP,               "image/x-bitmap" },
    { VLC_CODEC_BMP,               "image/x-ms-bmp" },
    { VLC_CODEC_PNM,               "image/x-portable-anymap" },
    { VLC_CODEC_PNM,               "image/x-portable-bitmap" },
    { VLC_CODEC_PNM,               "image/x-portable-graymap" },
    { VLC_CODEC_PNM,               "image/x-portable-pixmap" },
    { VLC_CODEC_GIF,               "image/gif" },
    { VLC_CODEC_JPEG,              "image/jpeg" },
    { VLC_CODEC_BPG,               "image/bpg" },
    { VLC_CODEC_FARBFELD,          "image/farbfeld" },
    { VLC_CODEC_PCX,               "image/pcx" },
    { VLC_CODEC_PNG,               "image/png" },
    { VLC_CODEC_QOI,               "image/qoi" },
    { VLC_CODEC_SVG,               "image/svg+xml" },
    { VLC_CODEC_TIFF,              "image/tiff" },
    { VLC_CODEC_TARGA,             "image/x-tga" },
    { VLC_CODEC_WEBP,              "image/webp" },
    { VLC_FOURCC('x','p','m',' '), "image/x-xpixmap" },
    { 0, NULL }
};

vlc_fourcc_t image_Mime2Fourcc( const char *psz_mime )
{
    for( int i = 0; mime_table[i].i_codec; i++ )
        if( !strcmp( psz_mime, mime_table[i].psz_mime ) )
            return mime_table[i].i_codec;
    return 0;
}

static vlc_decoder_device * image_get_device( decoder_t *p_dec )
{
    VLC_UNUSED(p_dec);
    return NULL; // no hardware decoding for now
}

static decoder_t *CreateDecoder( image_handler_t *p_image, const es_format_t *fmt )
{
    decoder_t *p_dec;
    struct decoder_owner *p_owner;

    p_owner = vlc_custom_create( p_image->p_parent, sizeof( *p_owner ), "image decoder" );
    if( p_owner == NULL )
        return NULL;
    p_dec = &p_owner->dec;
    p_owner->p_image = p_image;

    decoder_Init( p_dec, &p_owner->fmt_in, fmt );

    static const struct decoder_owner_callbacks dec_cbs =
    {
        .video = {
            .get_device = image_get_device,
            .queue = ImageQueueVideo,
        },
    };
    p_dec->cbs = &dec_cbs;

    /* Find a suitable decoder module */
    p_dec->p_module = module_need_var( p_dec, "video decoder", "codec" );
    if( !p_dec->p_module )
    {
        msg_Err( p_dec, "no suitable decoder module for fourcc `%4.4s'. "
                 "VLC probably does not support this image format.",
                 (char*)&p_dec->fmt_in->i_codec );

        decoder_Clean( p_dec );
        es_format_Clean( &p_owner->fmt_in );
        vlc_object_delete( p_dec );
        p_dec = NULL;
    }

    return p_dec;
}


static encoder_t *CreateEncoder( vlc_object_t *p_this, const video_format_t *fmt_in,
                                 vlc_fourcc_t codec, const video_format_t *fmt_out )
{
    encoder_t *p_enc;

    p_enc = sout_EncoderCreate( p_this, sizeof(encoder_t) );
    if( p_enc == NULL )
        return NULL;

    p_enc->p_module = NULL;
    es_format_InitFromVideo( &p_enc->fmt_in, fmt_in );

    if( fmt_out->i_width > 0 && fmt_out->i_height > 0 )
    {
        p_enc->fmt_in.video.i_width = fmt_out->i_width;
        p_enc->fmt_in.video.i_height = fmt_out->i_height;

        if( fmt_out->i_visible_width > 0 && fmt_out->i_visible_height > 0 )
        {
            p_enc->fmt_in.video.i_visible_width = fmt_out->i_visible_width;
            p_enc->fmt_in.video.i_visible_height = fmt_out->i_visible_height;
        }
        else
        {
            p_enc->fmt_in.video.i_visible_width = fmt_out->i_width;
            p_enc->fmt_in.video.i_visible_height = fmt_out->i_height;
        }
    }

    p_enc->fmt_in.video.i_frame_rate = 25;
    p_enc->fmt_in.video.i_frame_rate_base = 1;

    es_format_InitFromVideo( &p_enc->fmt_out, fmt_out );
    p_enc->fmt_out.i_codec = codec;
    p_enc->fmt_out.video.i_chroma = 0;
    p_enc->fmt_out.video.i_width = p_enc->fmt_in.video.i_width;
    p_enc->fmt_out.video.i_height = p_enc->fmt_in.video.i_height;
    p_enc->ops = NULL;

    /* Find a suitable decoder module */
    p_enc->p_module = module_need( p_enc, "image encoder", NULL, false );
    if( !p_enc->p_module )
    {
        msg_Err( p_enc, "no suitable encoder module for fourcc `%4.4s'.\n"
                 "VLC probably does not support this image format.",
                 (char*)&p_enc->fmt_out.i_codec );

        vlc_encoder_Destroy( p_enc );
        return NULL;
    }
    assert( p_enc->ops != NULL );

    return p_enc;
}

static filter_t *CreateConverter( vlc_object_t *p_this,
                                  const es_format_t *p_fmt_in,
                                  struct vlc_video_context *p_vctx_in,
                                  const video_format_t *p_fmt_out )
{
    filter_t *p_filter;

    p_filter = vlc_custom_create( p_this, sizeof(filter_t), "filter" );

    es_format_Copy( &p_filter->fmt_in, p_fmt_in );
    es_format_Copy( &p_filter->fmt_out, p_fmt_in );
    video_format_Copy( &p_filter->fmt_out.video, p_fmt_out );

    /* whatever the input offset, write at offset 0 in the target image */
    p_filter->fmt_out.video.i_x_offset = 0;
    p_filter->fmt_out.video.i_y_offset = 0;

    p_filter->fmt_out.i_codec = p_fmt_out->i_chroma;
    p_filter->vctx_in = p_vctx_in;
    p_filter->p_module = vlc_filter_LoadModule( p_filter, "video converter", NULL, false );

    if( !p_filter->p_module )
    {
        msg_Dbg( p_filter, "no video converter found" );
        DeleteConverter( p_filter );
        return NULL;
    }
    assert( p_filter->ops != NULL );

    return p_filter;
}

static void DeleteConverter( filter_t * p_filter )
{
    vlc_filter_UnloadModule( p_filter );

    es_format_Clean( &p_filter->fmt_in );
    es_format_Clean( &p_filter->fmt_out );

    vlc_object_delete(p_filter);
}