subsdec.c 27.4 KB
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/*****************************************************************************
 * subsdec.c : text subtitles decoder
 *****************************************************************************
 * Copyright (C) 2000-2006 the VideoLAN team
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 * $Id$
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 *
 * Authors: Gildas Bazin <gbazin@videolan.org>
 *          Samuel Hocevar <sam@zoy.org>
 *          Derk-Jan Hartman <hartman at videolan dot org>
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 *          Bernie Purcell <bitmap@videolan.org>
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 *
 * 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
 *****************************************************************************/

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#include "subsdec.h"
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/*****************************************************************************
 * Local prototypes
 *****************************************************************************/
static int  OpenDecoder   ( vlc_object_t * );
static void CloseDecoder  ( vlc_object_t * );

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static subpicture_t   *DecodeBlock   ( decoder_t *, block_t ** );
static subpicture_t   *ParseText     ( decoder_t *, block_t * );
static char           *StripTags      ( char * );
static char           *CreateHtmlSubtitle ( char * );

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/*****************************************************************************
 * Module descriptor.
 *****************************************************************************/
static const char *ppsz_encodings[] = { DEFAULT_NAME, "ASCII", "UTF-8", "",
    "ISO-8859-1", "CP1252", "MacRoman", "MacIceland","ISO-8859-15", "",
    "ISO-8859-2", "CP1250", "MacCentralEurope", "MacCroatian", "MacRomania", "",
    "ISO-8859-5", "CP1251", "MacCyrillic", "MacUkraine", "KOI8-R", "KOI8-U", "KOI8-RU", "",
    "ISO-8859-6", "CP1256", "MacArabic", "",
    "ISO-8859-7", "CP1253", "MacGreek", "",
    "ISO-8859-8", "CP1255", "MacHebrew", "",
    "ISO-8859-9", "CP1254", "MacTurkish", "",
    "ISO-8859-13", "CP1257", "",
    "ISO-2022-JP", "ISO-2022-JP-1", "ISO-2022-JP-2", "EUC-JP", "SHIFT_JIS", "",
    "ISO-2022-CN", "ISO-2022-CN-EXT", "EUC-CN", "EUC-TW", "BIG5", "BIG5-HKSCS", "",
    "ISO-2022-KR", "EUC-KR", "",
    "MacThai", "KOI8-T", "",
    "ISO-8859-3", "ISO-8859-4", "ISO-8859-10", "ISO-8859-14", "ISO-8859-16", "",
    "CP850", "CP862", "CP866", "CP874", "CP932", "CP949", "CP950", "CP1133", "CP1258", "",
    "Macintosh", "",
    "UTF-7", "UTF-16", "UTF-16BE", "UTF-16LE", "UTF-32", "UTF-32BE", "UTF-32LE",
    "C99", "JAVA", "UCS-2", "UCS-2BE", "UCS-2LE", "UCS-4", "UCS-4BE", "UCS-4LE", "",
    "HZ", "GBK", "GB18030", "JOHAB", "ARMSCII-8",
    "Georgian-Academy", "Georgian-PS", "TIS-620", "MuleLao-1", "VISCII", "TCVN",
    "HPROMAN8", "NEXTSTEP" };
/*
SSA supports charset selection.
The following known charsets are used:

0 = Ansi - Western European
1 = default
2 = symbol
3 = invalid
77 = Mac
128 = Japanese (Shift JIS)
129 = Hangul
130 = Johab
134 = GB2312 Simplified Chinese
136 = Big5 Traditional Chinese
161 = Greek
162 = Turkish
163 = Vietnamese
177 = Hebrew
178 = Arabic
186 = Baltic
204 = Russian (Cyrillic)
222 = Thai
238 = Eastern European
254 = PC 437
*/

static int  pi_justification[] = { 0, 1, 2 };
static const char *ppsz_justification_text[] = {N_("Center"),N_("Left"),N_("Right")};

#define ENCODING_TEXT N_("Subtitles text encoding")
#define ENCODING_LONGTEXT N_("Set the encoding used in text subtitles")
#define ALIGN_TEXT N_("Subtitles justification")
#define ALIGN_LONGTEXT N_("Set the justification of subtitles")
#define AUTODETECT_UTF8_TEXT N_("UTF-8 subtitles autodetection")
#define AUTODETECT_UTF8_LONGTEXT N_("This enables automatic detection of " \
            "UTF-8 encoding within subtitles files.")
#define FORMAT_TEXT N_("Formatted Subtitles")
#define FORMAT_LONGTEXT N_("Some subtitle formats allow for text formatting. " \
 "VLC partly implements this, but you can choose to disable all formatting.")


vlc_module_begin();
    set_shortname( _("Subtitles"));
    set_description( _("Text subtitles decoder") );
    set_capability( "decoder", 50 );
    set_callbacks( OpenDecoder, CloseDecoder );
    set_category( CAT_INPUT );
    set_subcategory( SUBCAT_INPUT_SCODEC );

    add_integer( "subsdec-align", 0, NULL, ALIGN_TEXT, ALIGN_LONGTEXT,
                 VLC_FALSE );
        change_integer_list( pi_justification, ppsz_justification_text, 0 );
    add_string( "subsdec-encoding", DEFAULT_NAME, NULL,
                ENCODING_TEXT, ENCODING_LONGTEXT, VLC_FALSE );
        change_string_list( ppsz_encodings, 0, 0 );
    add_bool( "subsdec-autodetect-utf8", VLC_TRUE, NULL,
              AUTODETECT_UTF8_TEXT, AUTODETECT_UTF8_LONGTEXT, VLC_FALSE );
    add_bool( "subsdec-formatted", VLC_TRUE, NULL, FORMAT_TEXT, FORMAT_LONGTEXT,
                 VLC_FALSE );
vlc_module_end();

/*****************************************************************************
 * OpenDecoder: probe the decoder and return score
 *****************************************************************************
 * Tries to launch a decoder and return score so that the interface is able
 * to chose.
 *****************************************************************************/
static int OpenDecoder( vlc_object_t *p_this )
{
    decoder_t     *p_dec = (decoder_t*)p_this;
    decoder_sys_t *p_sys;
    vlc_value_t    val;

    if( p_dec->fmt_in.i_codec != VLC_FOURCC('s','u','b','t') &&
        p_dec->fmt_in.i_codec != VLC_FOURCC('s','s','a',' ') )
    {
        return VLC_EGENERIC;
    }

    p_dec->pf_decode_sub = DecodeBlock;

    /* Allocate the memory needed to store the decoder's structure */
    if( ( p_dec->p_sys = p_sys =
          (decoder_sys_t *)calloc(1, sizeof(decoder_sys_t)) ) == NULL )
    {
        msg_Err( p_dec, "out of memory" );
        return VLC_ENOMEM;
    }

    /* init of p_sys */
    p_sys->i_align = 0;
    p_sys->iconv_handle = (vlc_iconv_t)-1;
    p_sys->b_autodetect_utf8 = VLC_FALSE;
    p_sys->b_ass = VLC_FALSE;
    p_sys->i_original_height = -1;
    p_sys->i_original_width = -1;
    TAB_INIT( p_sys->i_ssa_styles, p_sys->pp_ssa_styles );
    TAB_INIT( p_sys->i_images, p_sys->pp_images );

    char *psz_charset = NULL;
    /* First try demux-specified encoding */
    if( p_dec->fmt_in.subs.psz_encoding && *p_dec->fmt_in.subs.psz_encoding )
    {
        psz_charset = strdup (p_dec->fmt_in.subs.psz_encoding);
        msg_Dbg (p_dec, "trying demuxer-specified character encoding: %s",
                 p_dec->fmt_in.subs.psz_encoding ?: "not specified");
    }

    /* Second, try configured encoding */
    if (psz_charset == NULL)
    {
        psz_charset = var_CreateGetNonEmptyString (p_dec, "subsdec-encoding");
        if ((psz_charset != NULL) && !strcasecmp (psz_charset, DEFAULT_NAME))
        {
            free (psz_charset);
            psz_charset = NULL;
        }

        msg_Dbg (p_dec, "trying configured character encoding: %s",
                 psz_charset ?: "not specified");
    }

    /* Third, try "local" encoding with optional UTF-8 autodetection */
    if (psz_charset == NULL)
    {
        psz_charset = strdup (GetFallbackEncoding ());
        msg_Dbg (p_dec, "trying default character encoding: %s",
                 psz_charset ?: "not specified");

        if (var_CreateGetBool (p_dec, "subsdec-autodetect-utf8"))
        {
            msg_Dbg (p_dec, "using automatic UTF-8 detection");
            p_sys->b_autodetect_utf8 = VLC_TRUE;
        }
    }

    if (psz_charset == NULL)
    {
        psz_charset = strdup ("UTF-8");
        msg_Dbg (p_dec, "trying hard-coded character encoding: %s",
                 psz_charset ?: "error");
    }

    if (psz_charset == NULL)
    {
        free (p_sys);
        return VLC_ENOMEM;
    }

    if (strcasecmp (psz_charset, "UTF-8") && strcasecmp (psz_charset, "utf8"))
    {
        p_sys->iconv_handle = vlc_iconv_open ("UTF-8", psz_charset);
        if (p_sys->iconv_handle == (vlc_iconv_t)(-1))
            msg_Err (p_dec, "cannot convert from %s: %s", psz_charset,
                     strerror (errno));
    }
    free (psz_charset);

    var_Create( p_dec, "subsdec-align", VLC_VAR_INTEGER | VLC_VAR_DOINHERIT );
    var_Get( p_dec, "subsdec-align", &val );
    p_sys->i_align = val.i_int;

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    if( p_dec->fmt_in.i_codec == VLC_FOURCC('s','s','a',' ')
     && var_CreateGetBool( p_dec, "subsdec-formatted" ) )
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    {
        if( p_dec->fmt_in.i_extra > 0 )
            ParseSSAHeader( p_dec );
    }

    return VLC_SUCCESS;
}

/****************************************************************************
 * DecodeBlock: the whole thing
 ****************************************************************************
 * This function must be fed with complete subtitles units.
 ****************************************************************************/
static subpicture_t *DecodeBlock( decoder_t *p_dec, block_t **pp_block )
{
    subpicture_t *p_spu = NULL;

    if( !pp_block || *pp_block == NULL ) return NULL;

    p_spu = ParseText( p_dec, *pp_block );

    block_Release( *pp_block );
    *pp_block = NULL;

    return p_spu;
}

/*****************************************************************************
 * CloseDecoder: clean up the decoder
 *****************************************************************************/
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;

    if( p_sys->iconv_handle != (vlc_iconv_t)-1 )
        vlc_iconv_close( p_sys->iconv_handle );

    if( p_sys->pp_ssa_styles )
    {
        int i;
        for( i = 0; i < p_sys->i_ssa_styles; i++ )
        {
            if( !p_sys->pp_ssa_styles[i] )
                continue;

            if( p_sys->pp_ssa_styles[i]->psz_stylename )
                free( p_sys->pp_ssa_styles[i]->psz_stylename );
            if( p_sys->pp_ssa_styles[i]->font_style.psz_fontname )
                free( p_sys->pp_ssa_styles[i]->font_style.psz_fontname );
            if( p_sys->pp_ssa_styles[i] )
                free( p_sys->pp_ssa_styles[i] );
        }
        TAB_CLEAN( p_sys->i_ssa_styles, p_sys->pp_ssa_styles );
    }
    if( p_sys->pp_images )
    {
        int i;
        for( i = 0; i < p_sys->i_images; i++ )
        {
            if( !p_sys->pp_images[i] )
                continue;

            if( p_sys->pp_images[i]->p_pic )
                p_sys->pp_images[i]->p_pic->pf_release( p_sys->pp_images[i]->p_pic );
            if( p_sys->pp_images[i]->psz_filename )
                free( p_sys->pp_images[i]->psz_filename );

            free( p_sys->pp_images[i] );
        }
        TAB_CLEAN( p_sys->i_images, p_sys->pp_images );
    }

    free( p_sys );
}

/*****************************************************************************
 * ParseText: parse an text subtitle packet and send it to the video output
 *****************************************************************************/
static subpicture_t *ParseText( decoder_t *p_dec, block_t *p_block )
{
    decoder_sys_t *p_sys = p_dec->p_sys;
    subpicture_t *p_spu = NULL;
    char *psz_subtitle = NULL;
    video_format_t fmt;

    /* We cannot display a subpicture with no date */
    if( p_block->i_pts == 0 )
    {
        msg_Warn( p_dec, "subtitle without a date" );
        return NULL;
    }

    /* Check validity of packet data */
    /* An "empty" line containing only \0 can be used to force
       and ephemer picture from the screen */
    if( p_block->i_buffer < 1 )
    {
        msg_Warn( p_dec, "no subtitle data" );
        return NULL;
    }

    /* Should be resiliant against bad subtitles */
    psz_subtitle = strndup( (const char *)p_block->p_buffer,
                            p_block->i_buffer );
    if( psz_subtitle == NULL )
        return NULL;

    if( p_sys->iconv_handle == (vlc_iconv_t)-1 )
    {
        if (EnsureUTF8( psz_subtitle ) == NULL)
        {
            msg_Err( p_dec, _("failed to convert subtitle encoding.\n"
                     "Try manually setting a character-encoding "
                     "before you open the file.") );
        }
    }
    else
    {

        if( p_sys->b_autodetect_utf8 )
        {
            if( IsUTF8( psz_subtitle ) == NULL )
            {
                msg_Dbg( p_dec, "invalid UTF-8 sequence: "
                         "disabling UTF-8 subtitles autodetection" );
                p_sys->b_autodetect_utf8 = VLC_FALSE;
            }
        }

        if( !p_sys->b_autodetect_utf8 )
        {
            size_t inbytes_left = strlen( psz_subtitle );
            size_t outbytes_left = 6 * inbytes_left;
            char *psz_new_subtitle = malloc( outbytes_left + 1 );
            char *psz_convert_buffer_out = psz_new_subtitle;
            const char *psz_convert_buffer_in = psz_subtitle;

            size_t ret = vlc_iconv( p_sys->iconv_handle,
                                    &psz_convert_buffer_in, &inbytes_left,
                                    &psz_convert_buffer_out, &outbytes_left );

            *psz_convert_buffer_out++ = '\0';
            free( psz_subtitle );

            if( ( ret == (size_t)(-1) ) || inbytes_left )
            {
                free( psz_new_subtitle );
                msg_Err( p_dec, _("failed to convert subtitle encoding.\n"
                        "Try manually setting a character-encoding "
                                "before you open the file.") );
                return NULL;
            }

            psz_subtitle = realloc( psz_new_subtitle,
                                    psz_convert_buffer_out - psz_new_subtitle );
        }
    }

    /* Create the subpicture unit */
    p_spu = p_dec->pf_spu_buffer_new( p_dec );
    if( !p_spu )
    {
        msg_Warn( p_dec, "can't get spu buffer" );
        if( psz_subtitle ) free( psz_subtitle );
        return NULL;
    }

    p_spu->b_pausable = VLC_TRUE;

    /* Create a new subpicture region */
    memset( &fmt, 0, sizeof(video_format_t) );
    fmt.i_chroma = VLC_FOURCC('T','E','X','T');
    fmt.i_aspect = 0;
    fmt.i_width = fmt.i_height = 0;
    fmt.i_x_offset = fmt.i_y_offset = 0;
    p_spu->p_region = p_spu->pf_create_region( VLC_OBJECT(p_dec), &fmt );
    if( !p_spu->p_region )
    {
        msg_Err( p_dec, "cannot allocate SPU region" );
        if( psz_subtitle ) free( psz_subtitle );
        p_dec->pf_spu_buffer_del( p_dec, p_spu );
        return NULL;
    }

    /* Decode and format the subpicture unit */
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    if( p_dec->fmt_in.i_codec != VLC_FOURCC('s','s','a',' ') )
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    {
        /* Normal text subs, easy markup */
        p_spu->p_region->i_align = SUBPICTURE_ALIGN_BOTTOM | p_sys->i_align;
        p_spu->i_x = p_sys->i_align ? 20 : 0;
        p_spu->i_y = 10;

        /* Remove formatting from string */

        p_spu->p_region->psz_text = StripTags( psz_subtitle );
        if( var_CreateGetBool( p_dec, "subsdec-formatted" ) )
        {
            p_spu->p_region->psz_html = CreateHtmlSubtitle( psz_subtitle );
        }

        p_spu->i_start = p_block->i_pts;
        p_spu->i_stop = p_block->i_pts + p_block->i_length;
        p_spu->b_ephemer = (p_block->i_length == 0);
        p_spu->b_absolute = VLC_FALSE;
    }
    else
    {
        /* Decode SSA/USF strings */
        if( p_dec->fmt_in.i_codec == VLC_FOURCC('s','s','a',' ') )
            ParseSSAString( p_dec, psz_subtitle, p_spu );

        p_spu->i_start = p_block->i_pts;
        p_spu->i_stop = p_block->i_pts + p_block->i_length;
        p_spu->b_ephemer = (p_block->i_length == 0);
        p_spu->b_absolute = VLC_FALSE;
        p_spu->i_original_picture_width = p_sys->i_original_width;
        p_spu->i_original_picture_height = p_sys->i_original_height;
    }
    if( psz_subtitle ) free( psz_subtitle );

    return p_spu;
}

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char* GotoNextLine( char *psz_text )
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{
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    char *p_newline = psz_text;
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    while( p_newline[0] != '\0' )
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    {
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        if( p_newline[0] == '\n' || p_newline[0] == '\r' )
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        {
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            p_newline++;
            while( p_newline[0] == '\n' || p_newline[0] == '\r' )
                p_newline++;
            break;
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        }
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        else p_newline++;
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    }
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    return p_newline;
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}

/* Function now handles tags which has attribute values, and tries
 * to deal with &' commands too. It no longer modifies the string
 * in place, so that the original text can be reused
 */
static char *StripTags( char *psz_subtitle )
{
    char *psz_text_start;
    char *psz_text;

    psz_text = psz_text_start = malloc( strlen( psz_subtitle ) + 1 );
    if( !psz_text_start )
        return NULL;

    while( *psz_subtitle )
    {
        if( *psz_subtitle == '<' )
        {
            if( strncasecmp( psz_subtitle, "<br/>", 5 ) == 0 )
                *psz_text++ = '\n';

            psz_subtitle += strcspn( psz_subtitle, ">" );
        }
        else if( *psz_subtitle == '&' )
        {
            if( !strncasecmp( psz_subtitle, "&lt;", 4 ))
            {
                *psz_text++ = '<';
                psz_subtitle += strcspn( psz_subtitle, ";" );
            }
            else if( !strncasecmp( psz_subtitle, "&gt;", 4 ))
            {
                *psz_text++ = '>';
                psz_subtitle += strcspn( psz_subtitle, ";" );
            }
            else if( !strncasecmp( psz_subtitle, "&amp;", 5 ))
            {
                *psz_text++ = '&';
                psz_subtitle += strcspn( psz_subtitle, ";" );
            }
            else if( !strncasecmp( psz_subtitle, "&quot;", 6 ))
            {
                *psz_text++ = '\"';
                psz_subtitle += strcspn( psz_subtitle, ";" );
            }
            else
            {
                /* Assume it is just a normal ampersand */
                *psz_text++ = '&';
            }
        }
        else
        {
            *psz_text++ = *psz_subtitle;
        }

        psz_subtitle++;
    }
    *psz_text = '\0';
    psz_text_start = realloc( psz_text_start, strlen( psz_text_start ) + 1 );

    return psz_text_start;
}

/* Try to respect any style tags present in the subtitle string. The main
 * problem here is a lack of adequate specs for the subtitle formats.
 * SSA/ASS and USF are both detail spec'ed -- but they are handled elsewhere.
 * SAMI has a detailed spec, but extensive rework is needed in the demux
 * code to prevent all this style information being excised, as it presently
 * does.
 * That leaves the others - none of which were (I guess) originally intended
 * to be carrying style information. Over time people have used them that way.
 * In the absence of specifications from which to work, the tags supported
 * have been restricted to the simple set permitted by the USF DTD, ie. :
 *  Basic: <br>, <i>, <b>, <u>
 *  Extended: <font>
 *    Attributes: face
 *                family
 *                size
 *                color
 *                outline-color
 *                shadow-color
 *                outline-level
 *                shadow-level
 *                back-color
 *                alpha
 * There is also the further restriction that the subtitle be well-formed
 * as an XML entity, ie. the HTML sentence:
 *        <b><i>Bold and Italics</b></i>
 * doesn't qualify because the tags aren't nested one inside the other.
 * <text> tags are automatically added to the output to ensure
 * well-formedness.
 * If the text doesn't qualify for any reason, a NULL string is
 * returned, and the rendering engine will fall back to the
 * plain text version of the subtitle.
 */
static char *CreateHtmlSubtitle( char *psz_subtitle )
{
    char    psz_tagStack[ 100 ];
    size_t  i_buf_size     = strlen( psz_subtitle ) + 100;
    char   *psz_html_start = malloc( i_buf_size );

    psz_tagStack[ 0 ] = '\0';

    if( psz_html_start != NULL )
    {
        char *psz_html = psz_html_start;

        strcpy( psz_html, "<text>" );
        psz_html += 6;

        while( *psz_subtitle )
        {
            if( *psz_subtitle == '\n' )
            {
                strcpy( psz_html, "<br/>" );
                psz_html += 5;
                psz_subtitle++;
            }
            else if( *psz_subtitle == '<' )
            {
                if( !strncasecmp( psz_subtitle, "<br/>", 5 ))
                {
                    strcpy( psz_html, "<br/>" );
                    psz_html += 5;
                    psz_subtitle += 5;
                }
                else if( !strncasecmp( psz_subtitle, "<b>", 3 ) )
                {
                    strcpy( psz_html, "<b>" );
                    strcat( psz_tagStack, "b" );
                    psz_html += 3;
                    psz_subtitle += 3;
                }
                else if( !strncasecmp( psz_subtitle, "<i>", 3 ) )
                {
                    strcpy( psz_html, "<i>" );
                    strcat( psz_tagStack, "i" );
                    psz_html += 3;
                    psz_subtitle += 3;
                }
                else if( !strncasecmp( psz_subtitle, "<u>", 3 ) )
                {
                    strcpy( psz_html, "<u>" );
                    strcat( psz_tagStack, "u" );
                    psz_html += 3;
                    psz_subtitle += 3;
                }
                else if( !strncasecmp( psz_subtitle, "<font ", 6 ))
                {
                    const char *psz_attribs[] = { "face=\"", "family=\"", "size=\"",
                            "color=\"", "outline-color=\"", "shadow-color=\"",
                            "outline-level=\"", "shadow-level=\"", "back-color=\"",
                            "alpha=\"", NULL };

                    strcpy( psz_html, "<font " );
                    strcat( psz_tagStack, "f" );
                    psz_html += 6;
                    psz_subtitle += 6;

                    while( *psz_subtitle != '>' )
                    {
                        int  k;

                        for( k=0; psz_attribs[ k ]; k++ )
                        {
                            int i_len = strlen( psz_attribs[ k ] );

                            if( !strncasecmp( psz_subtitle, psz_attribs[ k ], i_len ))
                            {
                                i_len += strcspn( psz_subtitle + i_len, "\"" ) + 1;

                                strncpy( psz_html, psz_subtitle, i_len );
                                psz_html += i_len;
                                psz_subtitle += i_len;
                                break;
                            }
                        }
                        if( psz_attribs[ k ] == NULL )
                        {
                            /* Jump over unrecognised tag */
                            int i_len = strcspn( psz_subtitle, "\"" ) + 1;

                            i_len += strcspn( psz_subtitle + i_len, "\"" ) + 1;
                            psz_subtitle += i_len;
                        }
                        while (*psz_subtitle == ' ')
                            *psz_html++ = *psz_subtitle++;
                    }
                    *psz_html++ = *psz_subtitle++;
                }
                else if( !strncmp( psz_subtitle, "</", 2 ))
                {
                    vlc_bool_t  b_match     = VLC_FALSE;
                    int         i_len       = strlen( psz_tagStack ) - 1;
                    char       *psz_lastTag = NULL;

                    if( i_len >= 0 )
                    {
                        psz_lastTag = psz_tagStack + i_len;
                        i_len = 0;

                        switch( *psz_lastTag )
                        {
                            case 'b':
                                b_match = !strncasecmp( psz_subtitle, "</b>", 4 );
                                i_len   = 4;
                                break;
                            case 'i':
                                b_match = !strncasecmp( psz_subtitle, "</i>", 4 );
                                i_len   = 4;
                                break;
                            case 'u':
                                b_match = !strncasecmp( psz_subtitle, "</u>", 4 );
                                i_len   = 4;
                                break;
                            case 'f':
                                b_match = !strncasecmp( psz_subtitle, "</font>", 7 );
                                i_len   = 7;
                                break;
                        }
                    }
                    if( ! b_match )
                    {
                        /* Not well formed -- kill everything */
                        free( psz_html_start );
                        psz_html_start = NULL;
                        break;
                    }
                    *psz_lastTag = '\0';
                    strncpy( psz_html, psz_subtitle, i_len );
                    psz_html += i_len;
                    psz_subtitle += i_len;
                }
                else
                {
                    psz_subtitle += strcspn( psz_subtitle, ">" );
                }
            }
            else if( *psz_subtitle == '&' )
            {
                if( !strncasecmp( psz_subtitle, "&lt;", 4 ))
                {
                    strcpy( psz_html, "&lt;" );
                    psz_html += 4;
                    psz_subtitle += 4;
                }
                else if( !strncasecmp( psz_subtitle, "&gt;", 4 ))
                {
                    strcpy( psz_html, "&gt;" );
                    psz_html += 4;
                    psz_subtitle += 4;
                }
                else if( !strncasecmp( psz_subtitle, "&amp;", 5 ))
                {
                    strcpy( psz_html, "&amp;" );
                    psz_html += 5;
                    psz_subtitle += 5;
                }
                else
                {
                    strcpy( psz_html, "&amp;" );
                    psz_html += 5;
                    psz_subtitle++;
                }
            }
            else
            {
                *psz_html = *psz_subtitle;
                if( psz_html > psz_html_start )
                {
                    /* Check for double whitespace */
                    if((( *psz_html == ' ' ) ||
                        ( *psz_html == '\t' )) &&
                       (( *(psz_html-1) == ' ' ) ||
                        ( *(psz_html-1) == '\t' )))
                    {
                        strcpy( psz_html, NO_BREAKING_SPACE );
                        psz_html += strlen( NO_BREAKING_SPACE ) - 1;
                    }
                }
                psz_html++;
                psz_subtitle++;
            }

            if( ( size_t )( psz_html - psz_html_start ) > i_buf_size - 10 )
            {
                int i_len = psz_html - psz_html_start;

                i_buf_size += 100;
                psz_html_start = realloc( psz_html_start, i_buf_size );
                psz_html = psz_html_start + i_len;
                *psz_html = '\0';
            }
        }
        strcpy( psz_html, "</text>" );
        psz_html += 7;

        if( psz_tagStack[ 0 ] != '\0' )
        {
            /* Not well formed -- kill everything */
            free( psz_html_start );
            psz_html_start = NULL;
        }
        else if( psz_html_start )
        {
            /* Shrink the memory requirements */
            psz_html_start = realloc( psz_html_start,  psz_html - psz_html_start + 1 );
        }
    }
    return psz_html_start;
}