[libav-devel] [PATCH] matroskaenc: Produce valid chapter ids

[Martin Storsjö]

From: Michael Niedermayer <michae...@gmx.at>

Chapter ids need to start from 1 or higher in matroska. If
necessary, offset the chapter ids to the valid range.

Based on a patch by Fabian Neundorf.
---
Compared to the previous patch, this keeps the chapter ids intact
if remuxing from matroska (or any other source where the ids are
in the correct range to begin with).
---
 libavformat/matroskaenc.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index 67d2350..b030295 100644
--- a/libavformat/matroskaenc.c
+++ b/libavformat/matroskaenc.c
@@ -101,6 +101,8 @@ typedef struct MatroskaMuxContext {
 
     int reserve_cues_space;
     int64_t cues_pos;
+
+    int chapter_id_offset;
 } MatroskaMuxContext;
 
 
@@ -722,7 +724,7 @@ static int mkv_write_chapters(AVFormatContext *s)
         AVDictionaryEntry *t = NULL;
 
         chapteratom = start_ebml_master(pb, MATROSKA_ID_CHAPTERATOM, 0);
-        put_ebml_uint(pb, MATROSKA_ID_CHAPTERUID, c->id);
+        put_ebml_uint(pb, MATROSKA_ID_CHAPTERUID, c->id + 
mkv->chapter_id_offset);
         put_ebml_uint(pb, MATROSKA_ID_CHAPTERTIMESTART,
                       av_rescale_q(c->start, c->time_base, scale));
         put_ebml_uint(pb, MATROSKA_ID_CHAPTERTIMEEND,
@@ -803,6 +805,7 @@ static int mkv_write_tag(AVFormatContext *s, AVDictionary 
*m, unsigned int eleme
 
 static int mkv_write_tags(AVFormatContext *s)
 {
+    MatroskaMuxContext *mkv = s->priv_data;
     ebml_master tags = {0};
     int i, ret;
 
@@ -829,7 +832,7 @@ static int mkv_write_tags(AVFormatContext *s)
         if (!av_dict_get(ch->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))
             continue;
 
-        ret = mkv_write_tag(s, ch->metadata, 
MATROSKA_ID_TAGTARGETS_CHAPTERUID, ch->id, &tags);
+        ret = mkv_write_tag(s, ch->metadata, 
MATROSKA_ID_TAGTARGETS_CHAPTERUID, ch->id + mkv->chapter_id_offset, &tags);
         if (ret < 0) return ret;
     }
 
@@ -967,6 +970,9 @@ static int mkv_write_header(AVFormatContext *s)
     ret = mkv_write_tracks(s);
     if (ret < 0) return ret;
 
+    for (i = 0; i < s->nb_chapters; i++)
+        mkv->chapter_id_offset = FFMAX(mkv->chapter_id_offset, 1 - 
s->chapters[i]->id);
+
     if (mkv->mode != MODE_WEBM) {
         ret = mkv_write_chapters(s);
         if (ret < 0) return ret;
-- 
1.7.9.4

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