Universal Text Subtitle Support Initial Implementation

- Patch by davidfstr ... Thanks!
- Adds support for reading TEXT subtitle tracks from file inputs
- Tested combinations:
-- MKV UTF-8 -> MKV UTF-8 (passthru)
-- MKV UTF-8 -> MP4 TX3G (upconvert)
-- MP4 TX3G -> MKV UTF-8 (downconvert)
-- MP4 TX3G -> MP4 TX3G (downconvert to UTF-8 then upconvert)
- Further explained here http://forum.handbrake.fr/viewtopic.php?f=4&t=16099 

git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@3283 b64f7644-9d1e-0410-96f1-a4d463321fa5

8 files changed, 463 insertions, 10 deletions

diff --git a/libhb/common.h b/libhb/common.h
index 33c3da2f7..cdb4d9fe1 100644
--- a/libhb/common.h
+++ b/libhb/common.h
@@ -125,6 +125,8 @@ struct hb_subtitle_config_s
     enum subdest { RENDERSUB, PASSTHRUSUB } dest;
     int  force;
     int  default_track; 
+    
+    /* SRT subtitle tracks only */
     char src_filename[128];
     char src_codeset[40];
     int64_t offset;
@@ -465,6 +467,35 @@ struct hb_chapter_s
     char     title[1024];
 };
 
+/*
+ * A subtitle track.
+ * 
+ * Required fields when a demuxer creates a subtitle track are:
+ * > id
+ *     - ID of this track
+ *     - must be unique for all tracks within a single job,
+ *       since it is used to look up the appropriate in-FIFO with GetFifoForId()
+ * > format
+ *     - format of the packets the subtitle decoder work-object sends to sub->fifo_raw
+ *     - for passthru subtitles, is also the format of the final packets sent to sub->fifo_out
+ *     - PICTURESUB for banded 8-bit YAUV pixels
+ *     - TEXTSUB for UTF-8 text marked up with <b>, <i>, or <u>
+ *     - read by the muxers, and by the subtitle burn-in logic in the hb_sync_video work-object
+ * > source
+ *     - used to create the appropriate subtitle decoder work-object in do_job()
+ * > config.dest
+ *     - whether to render the subtitle on the video track (RENDERSUB) or 
+ *       to pass it through its own subtitle track in the output container (PASSTHRUSUB)
+ *     - for legacy compatibility, all newly created VOBSUB tracks should default to RENDERSUB
+ *     - since only VOBSUBs are renderable (as of 2010-04-25), all other newly created
+ *       subtitle track types should default to PASSTHRUSUB
+ * > lang
+ *     - user-readable description of the subtitle track
+ *     - may correspond to the language of the track (see the 'iso639_2' field)
+ *     - may correspond to the type of track (see the 'type' field; ex: "Closed Captions")
+ * > iso639_2
+ *     - language code for the subtitle, or "und" if unknown
+ */
 struct hb_subtitle_s
 {
     int  id;
@@ -473,7 +504,7 @@ struct hb_subtitle_s
     hb_subtitle_config_t config;
 
     enum subtype { PICTURESUB, TEXTSUB } format;
-    enum subsource { VOBSUB, SRTSUB, CC608SUB, CC708SUB } source;
+    enum subsource { VOBSUB, SRTSUB, CC608SUB, /*unused*/CC708SUB, UTF8SUB, TX3GSUB } source;
     char lang[1024];
     char iso639_2[4];
     uint8_t type; /* Closed Caption, Childrens, Directors etc */
@@ -693,6 +724,8 @@ extern hb_work_object_t hb_decvobsub;
 extern hb_work_object_t hb_encvobsub;
 extern hb_work_object_t hb_deccc608;
 extern hb_work_object_t hb_decsrtsub;
+extern hb_work_object_t hb_decutf8sub;
+extern hb_work_object_t hb_dectx3gsub;
 extern hb_work_object_t hb_render;
 extern hb_work_object_t hb_encavcodec;
 extern hb_work_object_t hb_encx264;
diff --git a/libhb/dectx3gsub.c b/libhb/dectx3gsub.c
new file mode 100644
index 000000000..fe413ad98
--- /dev/null
+++ b/libhb/dectx3gsub.c
@@ -0,0 +1,240 @@
+/* 
+   This file is part of the HandBrake source code.
+   Homepage: <http://handbrake.fr/>.
+   It may be used under the terms of the GNU General Public License. */
+
+/*
+ * Converts TX3G subtitles to UTF-8 subtitles with limited HTML-style markup (<b>, <i>, <u>).
+ * 
+ * TX3G == MPEG 4, Part 17 (ISO/IEC 14496-17) == 3GPP Timed Text (26.245)
+ * A full reference to the format can be found here:
+ * http://www.3gpp.org/ftp/Specs/html-info/26245.htm
+ * 
+ * @author David Foster (davidfstr)
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include "hb.h"
+
+typedef enum {
+    BOLD        = 0x1,
+    ITALIC      = 0x2,
+    UNDERLINE   = 0x4
+} FaceStyleFlag;
+
+#define NUM_FACE_STYLE_FLAGS 3
+#define MAX_OPEN_TAG_SIZE 3     // "<b>"
+#define MAX_CLOSE_TAG_SIZE 4    // "</b>"
+
+typedef struct {
+    uint16_t startChar;       // NOTE: indices in terms of *character* (not: byte) positions
+    uint16_t endChar;
+    uint16_t fontID;
+    uint8_t faceStyleFlags;   // FaceStyleFlag
+    uint8_t fontSize;
+    uint32_t textColorRGBA;
+} StyleRecord;
+
+// NOTE: None of these macros check for buffer overflow
+#define READ_U8()       *pos;                                                       pos += 1;
+#define READ_U16()      (pos[0] << 8) | pos[1];                                     pos += 2;
+#define READ_U32()      (pos[0] << 24) | (pos[1] << 16) | (pos[2] << 8) | pos[3];   pos += 4;
+#define READ_ARRAY(n)   pos;                                                        pos += n;
+
+#define WRITE_CHAR(c)       {dst[0]=c;                                              dst += 1;}
+#define WRITE_START_TAG(c)  {dst[0]='<'; dst[1]=c;   dst[2]='>';                    dst += 3;}
+#define WRITE_END_TAG(c)    {dst[0]='<'; dst[1]='/'; dst[2]=c; dst[3]='>';          dst += 4;}
+
+#define FOURCC(str)    ((((uint32_t) str[0]) << 24) | \
+                        (((uint32_t) str[1]) << 16) | \
+                        (((uint32_t) str[2]) << 8) | \
+                        (((uint32_t) str[3]) << 0))
+#define IS_10xxxxxx(c) ((c & 0xC0) == 0x80)
+
+static hb_buffer_t *tx3g_decode_to_utf8( hb_buffer_t *in )
+{
+    uint8_t *pos = in->data;
+    uint8_t *end = in->data + in->size;
+    
+    uint16_t numStyleRecords = 0;
+    
+    uint8_t *startStyle;
+    uint8_t *endStyle;
+    
+    /*
+     * Parse the packet as a TX3G TextSample.
+     * 
+     * Look for a single StyleBox ('styl') and read all contained StyleRecords.
+     * Ignore all other box types.
+     * 
+     * NOTE: Buffer overflows on read are not checked.
+     */
+    uint16_t textLength = READ_U16();
+    uint8_t *text = READ_ARRAY(textLength);
+    startStyle = calloc( textLength, 1 );
+    endStyle = calloc( textLength, 1 );
+    while ( pos < end ) {
+        /*
+         * Read TextSampleModifierBox
+         */
+        uint32_t size = READ_U32();
+        if ( size == 0 ) {
+            size = pos - end;   // extends to end of packet
+        }
+        if ( size == 1 ) {
+            hb_log( "dectx3gsub: TextSampleModifierBox has unsupported large size" );
+            break;
+        }
+        uint32_t type = READ_U32();
+        if ( type == FOURCC("uuid") ) {
+            hb_log( "dectx3gsub: TextSampleModifierBox has unsupported extended type" );
+            break;
+        }
+        
+        if ( type == FOURCC("styl") ) {
+            // Found a StyleBox. Parse the contained StyleRecords
+            
+            if ( numStyleRecords != 0 ) {
+                hb_log( "dectx3gsub: found additional StyleBoxes on subtitle; skipping" );
+                READ_ARRAY(size);
+                continue;
+            }
+            
+            numStyleRecords = READ_U16();
+            
+            int i;
+            for (i=0; i<numStyleRecords; i++) {
+                StyleRecord curRecord;
+                curRecord.startChar         = READ_U16();
+                curRecord.endChar           = READ_U16();
+                curRecord.fontID            = READ_U16();
+                curRecord.faceStyleFlags    = READ_U8();
+                curRecord.fontSize          = READ_U8();
+                curRecord.textColorRGBA     = READ_U32();
+                
+                startStyle[curRecord.startChar] |= curRecord.faceStyleFlags;
+                endStyle[curRecord.endChar]     |= curRecord.faceStyleFlags;
+            }
+        } else {
+            // Found some other kind of TextSampleModifierBox. Skip it.
+            READ_ARRAY(size);
+        }
+    }
+    
+    /*
+     * Copy text to output buffer, and add HTML markup for the style records
+     */
+    int maxOutputSize = textLength + (numStyleRecords * NUM_FACE_STYLE_FLAGS * (MAX_OPEN_TAG_SIZE + MAX_CLOSE_TAG_SIZE));
+    hb_buffer_t *out = hb_buffer_init( maxOutputSize );
+    uint8_t *dst = out->data;
+    int charIndex = 0;
+    for ( pos = text, end = text + textLength; pos < end; pos++ ) {
+        if (IS_10xxxxxx(*pos)) {
+            // Is a non-first byte of a multi-byte UTF-8 character
+            WRITE_CHAR(*pos);
+            continue;   // ...without incrementing 'charIndex'
+        }
+        
+        uint8_t plusStyles = startStyle[charIndex];
+        uint8_t minusStyles = endStyle[charIndex];
+        
+        if (minusStyles & UNDERLINE)
+            WRITE_END_TAG('u');
+        if (minusStyles & ITALIC)
+            WRITE_END_TAG('i');
+        if (minusStyles & BOLD)
+            WRITE_END_TAG('b');
+        
+        if (plusStyles & BOLD)
+            WRITE_START_TAG('b');
+        if (plusStyles & ITALIC)
+            WRITE_START_TAG('i');
+        if (plusStyles & UNDERLINE)
+            WRITE_START_TAG('u');
+        
+        WRITE_CHAR(*pos);
+        charIndex++;
+    }
+    
+    // Trim output buffer to the actual amount of data written
+    out->size = dst - out->data;
+    
+    // Copy metadata from the input packet to the output packet
+    out->start = in->start;
+    out->stop = in->stop;
+    
+    free( startStyle );
+    free( endStyle );
+    
+    return out;
+}
+
+#undef READ_U8
+#undef READ_U16
+#undef READ_U32
+#undef READ_ARRAY
+
+#undef WRITE_CHAR
+#undef WRITE_START_TAG
+#undef WRITE_END_TAG
+
+static int dectx3gInit( hb_work_object_t * w, hb_job_t * job )
+{
+    return 0;
+}
+
+static int dectx3gWork( hb_work_object_t * w, hb_buffer_t ** buf_in,
+                        hb_buffer_t ** buf_out )
+{
+    hb_buffer_t * in = *buf_in;
+    hb_buffer_t * out = NULL;
+    
+    // Warn if the subtitle's duration has not been passed through by the demuxer,
+    // which will prevent the subtitle from displaying at all
+    if ( in->stop == 0 ) {
+        hb_log( "dectx3gsub: subtitle packet lacks duration" );
+    }
+    
+    if ( in->size > 0 ) {
+        out = tx3g_decode_to_utf8(in);
+    } else {
+        out = hb_buffer_init( 0 );
+    }
+    
+    // We shouldn't be storing the extra NULL character,
+    // but the MP4 muxer expects this, unfortunately.
+    if ( out->size > 0 && out->data[out->size - 1] != '\0' ) {
+        // NOTE: out->size remains unchanged
+        hb_buffer_realloc( out, out->size + 1 );
+        out->data[out->size] = '\0';
+    }
+    
+    // If the input packet was non-empty, do not pass through
+    // an empty output packet (even if the subtitle was empty),
+    // as this would be interpreted as an end-of-stream
+    if ( in->size > 0 && out->size == 0 ) {
+        hb_buffer_close(&out);
+    }
+    
+    // Dispose the input packet, as it is no longer needed
+    hb_buffer_close(&in);
+    
+    *buf_in = NULL;
+    *buf_out = out;
+    return HB_WORK_OK;
+}
+
+static void dectx3gClose( hb_work_object_t * w )
+{
+    // nothing
+}
+
+hb_work_object_t hb_dectx3gsub =
+{
+    WORK_DECTX3GSUB,
+    "TX3G Subtitle Decoder",
+    dectx3gInit,
+    dectx3gWork,
+    dectx3gClose
+};
diff --git a/libhb/decutf8sub.c b/libhb/decutf8sub.c
new file mode 100644
index 000000000..dcd05d4fc
--- /dev/null
+++ b/libhb/decutf8sub.c
@@ -0,0 +1,64 @@
+/* 
+   This file is part of the HandBrake source code.
+   Homepage: <http://handbrake.fr/>.
+   It may be used under the terms of the GNU General Public License. */
+
+/*
+ * Decoder for UTF-8 subtitles obtained from file input-sources.
+ * 
+ * Input and output packet format is UTF-8 encoded text,
+ * with limited HTML-style markup (only <b>, <i>, and <u>).
+ * 
+ * @author David Foster (davidfstr)
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include "hb.h"
+
+static int decutf8Init( hb_work_object_t * w, hb_job_t * job )
+{
+    return 0;
+}
+
+static int decutf8Work( hb_work_object_t * w, hb_buffer_t ** buf_in,
+                        hb_buffer_t ** buf_out )
+{
+    hb_buffer_t * in = *buf_in;
+    hb_buffer_t * out = NULL;
+
+    // Pass the packets through without modification
+    out = in;
+
+    // Warn if the subtitle's duration has not been passed through by the demuxer,
+    // which will prevent the subtitle from displaying at all
+    if ( out->stop == 0 ) {
+        hb_log( "decutf8sub: subtitle packet lacks duration" );
+    }
+    
+    // We shouldn't be storing the extra NULL character,
+    // but the MP4 muxer expects this, unfortunately.
+    if ( out->size > 0 && out->data[out->size - 1] != '\0' ) {
+        // NOTE: out->size remains unchanged
+        hb_buffer_realloc( out, out->size + 1 );
+        out->data[out->size] = '\0';
+    }
+    
+    *buf_in = NULL;
+    *buf_out = out;
+    return HB_WORK_OK;
+}
+
+static void decutf8Close( hb_work_object_t * w )
+{
+    // nothing
+}
+
+hb_work_object_t hb_decutf8sub =
+{
+    WORK_DECUTF8SUB,
+    "UTF-8 Subtitle Decoder",
+    decutf8Init,
+    decutf8Work,
+    decutf8Close
+};
diff --git a/libhb/hb.c b/libhb/hb.c
index acdce5597..0c951f41d 100644
--- a/libhb/hb.c
+++ b/libhb/hb.c
@@ -276,6 +276,8 @@ hb_handle_t * hb_init( int verbose, int update_check )
     hb_register( &hb_encvobsub );
     hb_register( &hb_deccc608 );
     hb_register( &hb_decsrtsub );
+    hb_register( &hb_decutf8sub );
+    hb_register( &hb_dectx3gsub );
 	hb_register( &hb_render );
 	hb_register( &hb_encavcodec );
 	hb_register( &hb_encx264 );
@@ -377,6 +379,8 @@ hb_handle_t * hb_init_dl( int verbose, int update_check )
     hb_register( &hb_encvobsub );
     hb_register( &hb_deccc608 );
     hb_register( &hb_decsrtsub );
+    hb_register( &hb_decutf8sub );
+    hb_register( &hb_dectx3gsub );
 	hb_register( &hb_render );
 	hb_register( &hb_encavcodec );
 	hb_register( &hb_encx264 );
diff --git a/libhb/internal.h b/libhb/internal.h
index dd922dc46..dd217507d 100644
--- a/libhb/internal.h
+++ b/libhb/internal.h
@@ -38,19 +38,25 @@ void hb_set_state( hb_handle_t *, hb_state_t * );
 /***********************************************************************
  * fifo.c
  **********************************************************************/
+/*
+ * Holds a packet of data that is moving through the transcoding process.
+ * 
+ * May have metadata associated with it via extra fields
+ * that are conditionally used depending on the type of packet.
+ */
 struct hb_buffer_s
 {
-    int           size;
-    int           alloc;
-    uint8_t *     data;
-    int           cur;
+    int           size;     // size of this packet
+    int           alloc;    // used internally by the packet allocator (hb_buffer_init)
+    uint8_t *     data;     // packet data
+    int           cur;      // used internally by packet lists (hb_list_t)
 
     int64_t       sequence;
 
-    int           id;
-    int64_t       start;
-    int64_t       stop;
-    int           new_chap;
+    int           id;           // ID of the track that the packet comes from
+    int64_t       start;        // Video and subtitle packets: start time of frame/subtitle
+    int64_t       stop;         // Video and subtitle packets: stop time of frame/subtitle
+    int           new_chap;     // Video packets: ???
 
 #define HB_FRAME_IDR    0x01
 #define HB_FRAME_I      0x02
@@ -66,13 +72,20 @@ struct hb_buffer_s
     /* Holds the output PTS from x264, for use by b-frame offsets in muxmp4.c */
     int64_t     renderOffset;
 
+    // VOB subtitle packets:
+    //   Location and size of the subpicture.
     int           x;
     int           y;
     int           width;
     int           height;
 
+    // Video packets (after processing by the hb_sync_video work-object):
+    //   A (copy of a) VOB subtitle packet that needs to be burned into this video packet by the hb_render work-object.
+    //   Subtitles that are simply passed thru are NOT attached to the associated video packets.
     hb_buffer_t * sub;
 
+    // Packets in a list:
+    //   the next packet in the list
     hb_buffer_t * next;
 };
 
@@ -285,6 +298,8 @@ enum
     WORK_DECCC608,
     WORK_DECVOBSUB,
     WORK_DECSRTSUB,
+    WORK_DECUTF8SUB,
+    WORK_DECTX3GSUB,
     WORK_ENCVOBSUB,
     WORK_RENDER,
     WORK_ENCAVCODEC,
diff --git a/libhb/stream.c b/libhb/stream.c
index caed365cd..4b1bd98eb 100644
--- a/libhb/stream.c
+++ b/libhb/stream.c
@@ -2831,6 +2831,56 @@ static void add_ffmpeg_audio( hb_title_t *title, hb_stream_t *stream, int id )
     }
 }
 
+static void add_ffmpeg_subtitle( hb_title_t *title, hb_stream_t *stream, int id )
+{
+    AVStream *st = stream->ffmpeg_ic->streams[id];
+    AVCodecContext *codec = st->codec;
+    
+    hb_subtitle_t *subtitle = calloc( 1, sizeof(*subtitle) );
+    
+    subtitle->id = id;
+    
+    switch ( codec->codec_id )
+    {
+        // TODO(davidfstr): get universal VOB sub input working
+        /*
+        case CODEC_ID_DVD_SUBTITLE:
+            subtitle->format = PICTURESUB;
+            subtitle->source = VOBSUB;
+            subtitle->config.dest = RENDERSUB;  // By default render (burn-in) the VOBSUB.
+            break;
+        */
+        case CODEC_ID_TEXT:
+            subtitle->format = TEXTSUB;
+            subtitle->source = UTF8SUB;
+            subtitle->config.dest = PASSTHRUSUB;
+            break;
+        case CODEC_ID_MOV_TEXT: // TX3G
+            subtitle->format = TEXTSUB;
+            subtitle->source = TX3GSUB;
+            subtitle->config.dest = PASSTHRUSUB;
+            break;
+        // TODO(davidfstr): implement SSA subtitle support
+        /*
+        case CODEC_ID_SSA:
+            subtitle->format = TEXTSUB;
+            subtitle->source = SSASUB;
+            subtitle->config.dest = PASSTHRUSUB;
+            break;
+        */
+        default:
+            hb_log("add_ffmpeg_subtitle: unknown subtitle stream type: 0x%x", (int) codec->codec_id);
+            free(subtitle);
+            return;
+    }
+    
+    iso639_lang_t *language = lang_for_code2( st->language );
+    strcpy( subtitle->lang, language->eng_name );
+    strncpy( subtitle->iso639_2, language->iso639_2, 4 );
+    
+    hb_list_add(title->list_subtitle, subtitle);
+}
+
 static hb_title_t *ffmpeg_title_scan( hb_stream_t *stream )
 {
     AVFormatContext *ic = stream->ffmpeg_ic;
@@ -2887,6 +2937,10 @@ static hb_title_t *ffmpeg_title_scan( hb_stream_t *stream )
         {
             add_ffmpeg_audio( title, stream, i );
         }
+        else if ( ic->streams[i]->codec->codec_type == CODEC_TYPE_SUBTITLE )
+        {
+            add_ffmpeg_subtitle( title, stream, i );
+        }
     }
 
     title->container_name = strdup( ic->iformat->name );
@@ -3074,6 +3128,26 @@ static int ffmpeg_read( hb_stream_t *stream, hb_buffer_t *buf )
     {
         buf->renderOffset = buf->start;
     }
+    
+    /* 
+     * Fill out buf->stop for subtitle packets
+     * 
+     * libavcodec's MKV demuxer stores the duration of UTF-8 (TEXT) subtitles
+     * in the 'convergence_duration' field for some reason.
+     * 
+     * Other subtitles' durations are stored in the 'duration' field.
+     */
+    enum CodecID ffmpeg_pkt_codec = stream->ffmpeg_ic->streams[stream->ffmpeg_pkt->stream_index]->codec->codec_id;
+    if ( ffmpeg_pkt_codec == CODEC_ID_TEXT ) {
+        int64_t ffmpeg_pkt_duration = stream->ffmpeg_pkt->convergence_duration;
+        int64_t buf_duration = av_to_hb_pts( ffmpeg_pkt_duration, tsconv );
+        buf->stop = buf->start + buf_duration;
+    }
+    if ( ffmpeg_pkt_codec == CODEC_ID_MOV_TEXT ) {
+        int64_t ffmpeg_pkt_duration = stream->ffmpeg_pkt->duration;
+        int64_t buf_duration = av_to_hb_pts( ffmpeg_pkt_duration, tsconv );
+        buf->stop = buf->start + buf_duration;
+    }
 
     /*
      * Check to see whether this video buffer is on a chapter
diff --git a/libhb/sync.c b/libhb/sync.c
index a36b37b5b..36017801b 100644
--- a/libhb/sync.c
+++ b/libhb/sync.c
@@ -564,7 +564,9 @@ int syncVideoWork( hb_work_object_t * w, hb_buffer_t ** buf_in,
          */
         if( subtitle->source == CC608SUB ||
             subtitle->source == CC708SUB ||
-            subtitle->source == SRTSUB )
+            subtitle->source == SRTSUB ||
+            subtitle->source == UTF8SUB ||
+            subtitle->source == TX3GSUB)
         {
             /*
              * Rewrite timestamps on subtitles that came from Closed Captions
diff --git a/libhb/work.c b/libhb/work.c
index d2c8ac66b..838e50702 100644
--- a/libhb/work.c
+++ b/libhb/work.c
@@ -308,6 +308,8 @@ void hb_display_job_info( hb_job_t * job )
             hb_log( " * subtitle track %i, %s (id %x) %s [%s] -> %s ", subtitle->track, subtitle->lang, subtitle->id,
                     subtitle->format == PICTURESUB ? "Picture" : "Text",
                     subtitle->source == VOBSUB ? "VOBSUB" : 
+                    subtitle->source == UTF8SUB ? "UTF-8" : 
+                    subtitle->source == TX3GSUB ? "TX3G" : 
                     ((subtitle->source == CC608SUB ||
                       subtitle->source == CC708SUB) ? "CC" : "SRT"),
                     subtitle->config.dest == RENDERSUB ? "Render/Burn in" : "Pass-Through");
@@ -795,6 +797,25 @@ static void do_job( hb_job_t * job, int cpu_count )
                 w->subtitle = subtitle;
                 hb_list_add( job->list_work, w );
             }
+            
+            if( !job->indepth_scan && subtitle->source == UTF8SUB )
+            {
+                w = hb_get_work( WORK_DECUTF8SUB );
+                w->fifo_in  = subtitle->fifo_in;
+                w->fifo_out = subtitle->fifo_raw;
+                hb_list_add( job->list_work, w );
+            }
+            
+            if( !job->indepth_scan && subtitle->source == TX3GSUB )
+            {
+                // TODO(davidfstr): For MP4 containers, an alternate work-object
+                //                  should be used that just passes the packets through,
+                //                  instead of downconverting to UTF-8 subtitles.
+                w = hb_get_work( WORK_DECTX3GSUB );
+                w->fifo_in  = subtitle->fifo_in;
+                w->fifo_out = subtitle->fifo_raw;
+                hb_list_add( job->list_work, w );
+            }
 
             if( !job->indepth_scan && 
                 subtitle->format == PICTURESUB