avformat/matroskaenc: Don't waste bytes writing level 1 elements

Up until now, the length field of most level 1 elements has been written
using eight bytes, although it is known in advance how much space the
content of said elements will take up so that it would be possible to
determine the minimal amount of bytes for the length field. This
commit changes this.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: James Almer <jamrial@gmail.com>

1 files changed, 14 insertions, 15 deletions

diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index 15164bd87c..441315e2d5 100644
--- a/libavformat/matroskaenc.c
+++ b/libavformat/matroskaenc.c
@@ -60,7 +60,7 @@
 typedef struct ebml_master {
     int64_t         pos;                ///< absolute offset in the containing AVIOContext where the size field starts
                                         ///< for level 1 elements or else where the master's elements start
-    int             sizebytes;          ///< how many bytes were reserved/shall be used for the size
+    int             sizebytes;          ///< how many bytes were reserved for the size
 } ebml_master;
 
 typedef struct mkv_seekhead_entry {
@@ -334,15 +334,15 @@ static void end_ebml_master(AVIOContext *pb, ebml_master master)
 }
 
 static int start_ebml_master_crc32(AVIOContext *pb, AVIOContext **dyn_cp, MatroskaMuxContext *mkv,
-                                   ebml_master *master, uint32_t elementid, uint64_t expectedsize)
+                                   ebml_master *master, uint32_t elementid)
 {
-    int ret, bytes = expectedsize ? ebml_num_size(expectedsize) : 8;
+    int ret;
 
     if ((ret = avio_open_dyn_buf(dyn_cp)) < 0)
         return ret;
 
     put_ebml_id(pb, elementid);
-    *master = (ebml_master) { avio_tell(pb), bytes };
+    *master = (ebml_master) { avio_tell(pb), 0 };
     if (mkv->write_crc)
         put_ebml_void(*dyn_cp, 6); /* Reserve space for CRC32 so position/size calculations using avio_tell() take it into account */
 
@@ -356,7 +356,7 @@ static void end_ebml_master_crc32(AVIOContext *pb, AVIOContext **dyn_cp, Matrosk
     int size, skip = 0;
 
     size = avio_close_dyn_buf(*dyn_cp, &buf);
-    put_ebml_num(pb, size, master.sizebytes);
+    put_ebml_num(pb, size, 0);
     if (mkv->write_crc) {
         skip = 6; /* Skip reserved 6-byte long void element from the dynamic buffer. */
         AV_WL32(crc, av_crc(av_crc_get_table(AV_CRC_32_IEEE_LE), UINT32_MAX, buf + skip, size - skip) ^ UINT32_MAX);
@@ -377,7 +377,7 @@ static void end_ebml_master_crc32_preliminary(AVIOContext *pb, AVIOContext **dyn
     uint8_t *buf;
     int size = avio_get_dyn_buf(*dyn_cp, &buf);
 
-    put_ebml_num(pb, size, master.sizebytes);
+    put_ebml_num(pb, size, 0);
     avio_write(pb, buf, size);
 }
 
@@ -502,8 +502,7 @@ static int64_t mkv_write_seekhead(AVIOContext *pb, MatroskaMuxContext *mkv)
         }
     }
 
-    if (start_ebml_master_crc32(pb, &dyn_cp, mkv, &metaseek, MATROSKA_ID_SEEKHEAD,
-                                seekhead->reserved_size) < 0) {
+    if (start_ebml_master_crc32(pb, &dyn_cp, mkv, &metaseek, MATROSKA_ID_SEEKHEAD) < 0) {
         currentpos = -1;
         goto fail;
     }
@@ -578,7 +577,7 @@ static int64_t mkv_write_cues(AVFormatContext *s, mkv_cues *cues, mkv_track *tra
     int i, j, ret;
 
     currentpos = avio_tell(pb);
-    ret = start_ebml_master_crc32(pb, &dyn_cp, mkv, &cues_element, MATROSKA_ID_CUES, 0);
+    ret = start_ebml_master_crc32(pb, &dyn_cp, mkv, &cues_element, MATROSKA_ID_CUES);
     if (ret < 0)
         return ret;
 
@@ -1454,7 +1453,7 @@ static int mkv_write_tracks(AVFormatContext *s)
     if (ret < 0)
         return ret;
 
-    ret = start_ebml_master_crc32(pb, &mkv->tracks_bc, mkv, &mkv->tracks_master, MATROSKA_ID_TRACKS, 0);
+    ret = start_ebml_master_crc32(pb, &mkv->tracks_bc, mkv, &mkv->tracks_master, MATROSKA_ID_TRACKS);
     if (ret < 0)
         return ret;
 
@@ -1490,7 +1489,7 @@ static int mkv_write_chapters(AVFormatContext *s)
     ret = mkv_add_seekhead_entry(mkv->seekhead, MATROSKA_ID_CHAPTERS, avio_tell(pb));
     if (ret < 0) return ret;
 
-    ret = start_ebml_master_crc32(pb, &dyn_cp, mkv, &chapters, MATROSKA_ID_CHAPTERS, 0);
+    ret = start_ebml_master_crc32(pb, &dyn_cp, mkv, &chapters, MATROSKA_ID_CHAPTERS);
     if (ret < 0) return ret;
 
     editionentry = start_ebml_master(dyn_cp, MATROSKA_ID_EDITIONENTRY, 0);
@@ -1581,7 +1580,7 @@ static int mkv_write_tag_targets(AVFormatContext *s, uint32_t elementid,
         ret = mkv_add_seekhead_entry(mkv->seekhead, MATROSKA_ID_TAGS, avio_tell(s->pb));
         if (ret < 0) return ret;
 
-        start_ebml_master_crc32(s->pb, &mkv->tags_bc, mkv, tags, MATROSKA_ID_TAGS, 0);
+        start_ebml_master_crc32(s->pb, &mkv->tags_bc, mkv, tags, MATROSKA_ID_TAGS);
     }
     pb = mkv->tags_bc;
 
@@ -1748,7 +1747,7 @@ static int mkv_write_attachments(AVFormatContext *s)
     ret = mkv_add_seekhead_entry(mkv->seekhead, MATROSKA_ID_ATTACHMENTS, avio_tell(pb));
     if (ret < 0) return ret;
 
-    ret = start_ebml_master_crc32(pb, &dyn_cp, mkv, &attachments, MATROSKA_ID_ATTACHMENTS, 0);
+    ret = start_ebml_master_crc32(pb, &dyn_cp, mkv, &attachments, MATROSKA_ID_ATTACHMENTS);
     if (ret < 0) return ret;
 
     for (i = 0; i < s->nb_streams; i++) {
@@ -1907,7 +1906,7 @@ static int mkv_write_header(AVFormatContext *s)
     ret = mkv_add_seekhead_entry(mkv->seekhead, MATROSKA_ID_INFO, avio_tell(pb));
     if (ret < 0) goto fail;
 
-    ret = start_ebml_master_crc32(pb, &mkv->info_bc, mkv, &mkv->info, MATROSKA_ID_INFO, 0);
+    ret = start_ebml_master_crc32(pb, &mkv->info_bc, mkv, &mkv->info, MATROSKA_ID_INFO);
     if (ret < 0)
         return ret;
     pb = mkv->info_bc;
@@ -2400,7 +2399,7 @@ static int mkv_write_packet_internal(AVFormatContext *s, AVPacket *pkt, int add_
 
     if (mkv->cluster_pos == -1) {
         mkv->cluster_pos = avio_tell(s->pb);
-        ret = start_ebml_master_crc32(s->pb, &mkv->cluster_bc, mkv, &mkv->cluster, MATROSKA_ID_CLUSTER, 0);
+        ret = start_ebml_master_crc32(s->pb, &mkv->cluster_bc, mkv, &mkv->cluster, MATROSKA_ID_CLUSTER);
         if (ret < 0)
             return ret;
         put_ebml_uint(mkv->cluster_bc, MATROSKA_ID_CLUSTERTIMECODE, FFMAX(0, ts));