movenc: Fix muxing of Apple Quicktime chapters. v3

There is basic support for muxing chapter information into the
Apple Quicktime format already, but there are two errors which
prevent correct detection on the player side.

1) A special apple 'text' atom needs to be included inside the
gmhd atom.

2) The *different* 'text' atom inside the 'stsd' atom needs a
proper header.

With these changes, the chapters are now picked up by Apple
players and reported correctly by tools like mediainfo and mp4chaps.

v3 Update: The stub TextSampleEntry creation is moved to where the
chapter track is created so it's now specific to this track.

Signed-off-by: Philip Langdale <philipl@overt.org>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/movenc.c

@@ -1262,7 +1262,7 @@ static int mov_write_nmhd_tag(AVIOContext *pb)
 
 static int mov_write_gmhd_tag(AVIOContext *pb)
 {
-    avio_wb32(pb, 0x20);   /* size */
+    avio_wb32(pb, 0x4C);   /* size */
     ffio_wfourcc(pb, "gmhd");
     avio_wb32(pb, 0x18);   /* gmin size */
     ffio_wfourcc(pb, "gmin");/* generic media info */
@@ -1273,7 +1273,27 @@ static int mov_write_gmhd_tag(AVIOContext *pb)
     avio_wb16(pb, 0x8000); /* opColor (b?) */
     avio_wb16(pb, 0);      /* balance */
     avio_wb16(pb, 0);      /* reserved */
-    return 0x20;
+
+    /*
+     * This special text atom is required for
+     * Apple Quicktime chapters. The contents
+     * don't appear to be documented, so the
+     * bytes are copied verbatim.
+     */
+    avio_wb32(pb, 0x2C);   /* size */
+    ffio_wfourcc(pb, "text");
+    avio_wb16(pb, 0x01);
+    avio_wb32(pb, 0x00);
+    avio_wb32(pb, 0x00);
+    avio_wb32(pb, 0x00);
+    avio_wb32(pb, 0x01);
+    avio_wb32(pb, 0x00);
+    avio_wb32(pb, 0x00);
+    avio_wb32(pb, 0x00);
+    avio_wb32(pb, 0x00004000);
+    avio_wb16(pb, 0x0000);
+
+    return 0x4C;
 }
 
 static int mov_write_smhd_tag(AVIOContext *pb)
@@ -3052,6 +3072,8 @@ static int mov_write_packet(AVFormatContext *s, AVPacket *pkt)
 // as samples, and a tref pointing from the other tracks to the chapter one.
 static void mov_create_chapter_track(AVFormatContext *s, int tracknum)
 {
+    AVIOContext *pb;
+
     MOVMuxContext *mov = s->priv_data;
     MOVTrack *track = &mov->tracks[tracknum];
     AVPacket pkt = { .stream_index = tracknum, .flags = AV_PKT_FLAG_KEY };
@@ -3063,6 +3085,50 @@ static void mov_create_chapter_track(AVFormatContext *s, int tracknum)
     track->enc = avcodec_alloc_context3(NULL);
     track->enc->codec_type = AVMEDIA_TYPE_SUBTITLE;
 
+    if (avio_open_dyn_buf(&pb) >= 0) {
+        int size;
+        uint8_t *buf;
+
+        /* Stub header (usually for Quicktime chapter track) */
+        // TextSampleEntry
+        avio_wb32(pb, 0x01); // displayFlags
+        avio_w8(pb, 0x00);   // horizontal justification
+        avio_w8(pb, 0x00);   // vertical justification
+        avio_w8(pb, 0x00);   // bgColourRed
+        avio_w8(pb, 0x00);   // bgColourGreen
+        avio_w8(pb, 0x00);   // bgColourBlue
+        avio_w8(pb, 0x00);   // bgColourAlpha
+        // BoxRecord
+        avio_wb16(pb, 0x00); // defTextBoxTop
+        avio_wb16(pb, 0x00); // defTextBoxLeft
+        avio_wb16(pb, 0x00); // defTextBoxBottom
+        avio_wb16(pb, 0x00); // defTextBoxRight
+        // StyleRecord
+        avio_wb16(pb, 0x00); // startChar
+        avio_wb16(pb, 0x00); // endChar
+        avio_wb16(pb, 0x01); // fontID
+        avio_w8(pb, 0x00);   // fontStyleFlags
+        avio_w8(pb, 0x00);   // fontSize
+        avio_w8(pb, 0x00);   // fgColourRed
+        avio_w8(pb, 0x00);   // fgColourGreen
+        avio_w8(pb, 0x00);   // fgColourBlue
+        avio_w8(pb, 0x00);   // fgColourAlpha
+        // FontTableBox
+        avio_wb32(pb, 0x0D); // box size
+        ffio_wfourcc(pb, "ftab"); // box atom name
+        avio_wb16(pb, 0x01); // entry count
+        // FontRecord
+        avio_wb16(pb, 0x01); // font ID
+        avio_w8(pb, 0x00);   // font name length
+
+        if ((size = avio_close_dyn_buf(pb, &buf)) > 0) {
+            track->enc->extradata = buf;
+            track->enc->extradata_size = size;
+        } else {
+            av_free(&buf);
+        }
+    }
+
     for (i = 0; i < s->nb_chapters; i++) {
         AVChapter *c = s->chapters[i];
         AVDictionaryEntry *t;