avformat/matroskaenc: Avoid allocations for SeekHead

Up until e7ddafd5, the Matroska muxer wrote two SeekHeads: One at the
beginning referencing the main level 1 elements (i.e. not the Clusters)
and one at the end, referencing the Clusters. This second SeekHead was
useless and has therefore been removed. Yet the SeekHead-related
functions and structures are still geared towards this usecase: They
are built around an allocated array of variable size that gets
reallocated every time an element is added to it although the maximum
number of Seek entries is a small compile-time constant, so that one should
rather include the array in the SeekHead structure itself; and said
structure should be contained in the MatroskaMuxContext instead of being
allocated separately.

The earlier code reserved space for a SeekHead with 10 entries, although
we currently write at most 6. Reducing said number implied that every
Matroska/Webm file will be 84 bytes smaller and required to adapt
several FATE tests; furthermore, the reserved amount overestimated the
amount needed for for the SeekHead's length field and how many bytes
need to be reserved to write a EBML Void element, bringing the total
reduction to 89 bytes.

This also fixes a potential segfault: If !mkv->is_live and if the
AVIOContext is initially unseekable when writing the header, the
SeekHead is already written when writing the header and this used to
free the SeekHead-related structures that have been allocated. But if
the AVIOContext happens to be seekable when writing the trailer, it will
be attempted to write the SeekHead again which will lead to segfaults
because the corresponding structures have already been freed.

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

8 files changed, 35 insertions, 35 deletions

diff --git a/tests/ref/fate/aac-autobsf-adtstoasc b/tests/ref/fate/aac-autobsf-adtstoasc
index 9bf9dfe78f..45b68b62bd 100644
--- a/tests/ref/fate/aac-autobsf-adtstoasc
+++ b/tests/ref/fate/aac-autobsf-adtstoasc
@@ -1,5 +1,5 @@
-b09fc2f554712adbf84fe7899eb679d4 *tests/data/fate/aac-autobsf-adtstoasc.matroska
-6695 tests/data/fate/aac-autobsf-adtstoasc.matroska
+d10b73732b32f6b2f08885b40c41c77f *tests/data/fate/aac-autobsf-adtstoasc.matroska
+6606 tests/data/fate/aac-autobsf-adtstoasc.matroska
 #extradata 0:        2, 0x0030001c
 #tb 0: 1/1000
 #media_type 0: audio
diff --git a/tests/ref/fate/binsub-mksenc b/tests/ref/fate/binsub-mksenc
index 4b13ef217a..3266501de6 100644
--- a/tests/ref/fate/binsub-mksenc
+++ b/tests/ref/fate/binsub-mksenc
@@ -1 +1 @@
-a5811caa0caba3a3f9a449b91569745c
+03d376cc2e8622e7af540d4d9809dbf7
diff --git a/tests/ref/fate/rgb24-mkv b/tests/ref/fate/rgb24-mkv
index b9db53f592..43b4ee2e19 100644
--- a/tests/ref/fate/rgb24-mkv
+++ b/tests/ref/fate/rgb24-mkv
@@ -1,5 +1,5 @@
-ffe2c21083d56764aaae7945fd146326 *tests/data/fate/rgb24-mkv.matroska
-58305 tests/data/fate/rgb24-mkv.matroska
+92861b36a8220a3dae10d91cba614892 *tests/data/fate/rgb24-mkv.matroska
+58216 tests/data/fate/rgb24-mkv.matroska
 #tb 0: 1/10
 #media_type 0: video
 #codec_id 0: rawvideo
diff --git a/tests/ref/lavf-fate/av1.mkv b/tests/ref/lavf-fate/av1.mkv
index 242c63a541..bd8ae6eefa 100644
--- a/tests/ref/lavf-fate/av1.mkv
+++ b/tests/ref/lavf-fate/av1.mkv
@@ -1,3 +1,3 @@
-6604d339d44864be58b8580fe2fb52cc *tests/data/lavf-fate/lavf.av1.mkv
-55725 tests/data/lavf-fate/lavf.av1.mkv
+be4903a6a6710043383c8f38a535a8d3 *tests/data/lavf-fate/lavf.av1.mkv
+55636 tests/data/lavf-fate/lavf.av1.mkv
 tests/data/lavf-fate/lavf.av1.mkv CRC=0x7c27cc15
diff --git a/tests/ref/lavf/mka b/tests/ref/lavf/mka
index a244893cf2..e8239442e9 100644
--- a/tests/ref/lavf/mka
+++ b/tests/ref/lavf/mka
@@ -1,3 +1,3 @@
-a91bfdb08ff5a1e62b039748d16b07f7 *tests/data/lavf/lavf.mka
-43652 tests/data/lavf/lavf.mka
+58936d3ad4eb1372bd2e5845963fe17c *tests/data/lavf/lavf.mka
+43563 tests/data/lavf/lavf.mka
 tests/data/lavf/lavf.mka CRC=0x3a1da17e
diff --git a/tests/ref/lavf/mkv b/tests/ref/lavf/mkv
index 05999b79fb..4d73fbf39d 100644
--- a/tests/ref/lavf/mkv
+++ b/tests/ref/lavf/mkv
@@ -1,3 +1,3 @@
-3cddd26ed41f34925d3f34acabab174e *tests/data/lavf/lavf.mkv
-320555 tests/data/lavf/lavf.mkv
+6ec6d6a058a85bf616e0b981bb8e383f *tests/data/lavf/lavf.mkv
+320466 tests/data/lavf/lavf.mkv
 tests/data/lavf/lavf.mkv CRC=0xec6c3c68
diff --git a/tests/ref/lavf/mkv_attachment b/tests/ref/lavf/mkv_attachment
index 230dff369a..2e9711483f 100644
--- a/tests/ref/lavf/mkv_attachment
+++ b/tests/ref/lavf/mkv_attachment
@@ -1,3 +1,3 @@
-4a25c53150c09537cd4fcbff8f8f14ff *tests/data/lavf/lavf.mkv_attachment
-472706 tests/data/lavf/lavf.mkv_attachment
+41b4f132ada6e0faedf92e909526a899 *tests/data/lavf/lavf.mkv_attachment
+472617 tests/data/lavf/lavf.mkv_attachment
 tests/data/lavf/lavf.mkv_attachment CRC=0xec6c3c68
diff --git a/tests/ref/seek/lavf-mkv b/tests/ref/seek/lavf-mkv
index 6ed1f3a763..223e098829 100644
--- a/tests/ref/seek/lavf-mkv
+++ b/tests/ref/seek/lavf-mkv
@@ -1,48 +1,48 @@
-ret: 0         st: 1 flags:1 dts: 0.000000 pts: 0.000000 pos:    803 size:   208
+ret: 0         st: 1 flags:1 dts: 0.000000 pts: 0.000000 pos:    714 size:   208
 ret: 0         st:-1 flags:0  ts:-1.000000
-ret: 0         st: 0 flags:1 dts: 0.011000 pts: 0.011000 pos:   1019 size: 27837
+ret: 0         st: 0 flags:1 dts: 0.011000 pts: 0.011000 pos:    930 size: 27837
 ret: 0         st:-1 flags:1  ts: 1.894167
-ret: 0         st: 0 flags:1 dts: 0.971000 pts: 0.971000 pos: 292435 size: 27834
+ret: 0         st: 0 flags:1 dts: 0.971000 pts: 0.971000 pos: 292346 size: 27834
 ret: 0         st: 0 flags:0  ts: 0.788000
-ret: 0         st: 0 flags:1 dts: 0.971000 pts: 0.971000 pos: 292435 size: 27834
+ret: 0         st: 0 flags:1 dts: 0.971000 pts: 0.971000 pos: 292346 size: 27834
 ret: 0         st: 0 flags:1  ts:-0.317000
-ret: 0         st: 0 flags:1 dts: 0.011000 pts: 0.011000 pos:   1019 size: 27837
+ret: 0         st: 0 flags:1 dts: 0.011000 pts: 0.011000 pos:    930 size: 27837
 ret:-1         st: 1 flags:0  ts: 2.577000
 ret: 0         st: 1 flags:1  ts: 1.471000
-ret: 0         st: 1 flags:1 dts: 0.993000 pts: 0.993000 pos: 320276 size:   209
+ret: 0         st: 1 flags:1 dts: 0.993000 pts: 0.993000 pos: 320187 size:   209
 ret: 0         st:-1 flags:0  ts: 0.365002
-ret: 0         st: 0 flags:1 dts: 0.491000 pts: 0.491000 pos: 146987 size: 27925
+ret: 0         st: 0 flags:1 dts: 0.491000 pts: 0.491000 pos: 146898 size: 27925
 ret: 0         st:-1 flags:1  ts:-0.740831
-ret: 0         st: 0 flags:1 dts: 0.011000 pts: 0.011000 pos:   1019 size: 27837
+ret: 0         st: 0 flags:1 dts: 0.011000 pts: 0.011000 pos:    930 size: 27837
 ret:-1         st: 0 flags:0  ts: 2.153000
 ret: 0         st: 0 flags:1  ts: 1.048000
-ret: 0         st: 0 flags:1 dts: 0.971000 pts: 0.971000 pos: 292435 size: 27834
+ret: 0         st: 0 flags:1 dts: 0.971000 pts: 0.971000 pos: 292346 size: 27834
 ret: 0         st: 1 flags:0  ts:-0.058000
-ret: 0         st: 1 flags:1 dts: 0.000000 pts: 0.000000 pos:    803 size:   208
+ret: 0         st: 1 flags:1 dts: 0.000000 pts: 0.000000 pos:    714 size:   208
 ret: 0         st: 1 flags:1  ts: 2.836000
-ret: 0         st: 1 flags:1 dts: 0.993000 pts: 0.993000 pos: 320276 size:   209
+ret: 0         st: 1 flags:1 dts: 0.993000 pts: 0.993000 pos: 320187 size:   209
 ret:-1         st:-1 flags:0  ts: 1.730004
 ret: 0         st:-1 flags:1  ts: 0.624171
-ret: 0         st: 0 flags:1 dts: 0.491000 pts: 0.491000 pos: 146987 size: 27925
+ret: 0         st: 0 flags:1 dts: 0.491000 pts: 0.491000 pos: 146898 size: 27925
 ret: 0         st: 0 flags:0  ts:-0.482000
-ret: 0         st: 0 flags:1 dts: 0.011000 pts: 0.011000 pos:   1019 size: 27837
+ret: 0         st: 0 flags:1 dts: 0.011000 pts: 0.011000 pos:    930 size: 27837
 ret: 0         st: 0 flags:1  ts: 2.413000
-ret: 0         st: 0 flags:1 dts: 0.971000 pts: 0.971000 pos: 292435 size: 27834
+ret: 0         st: 0 flags:1 dts: 0.971000 pts: 0.971000 pos: 292346 size: 27834
 ret:-1         st: 1 flags:0  ts: 1.307000
 ret: 0         st: 1 flags:1  ts: 0.201000
-ret: 0         st: 1 flags:1 dts: 0.000000 pts: 0.000000 pos:    803 size:   208
+ret: 0         st: 1 flags:1 dts: 0.000000 pts: 0.000000 pos:    714 size:   208
 ret: 0         st:-1 flags:0  ts:-0.904994
-ret: 0         st: 0 flags:1 dts: 0.011000 pts: 0.011000 pos:   1019 size: 27837
+ret: 0         st: 0 flags:1 dts: 0.011000 pts: 0.011000 pos:    930 size: 27837
 ret: 0         st:-1 flags:1  ts: 1.989173
-ret: 0         st: 0 flags:1 dts: 0.971000 pts: 0.971000 pos: 292435 size: 27834
+ret: 0         st: 0 flags:1 dts: 0.971000 pts: 0.971000 pos: 292346 size: 27834
 ret: 0         st: 0 flags:0  ts: 0.883000
-ret: 0         st: 0 flags:1 dts: 0.971000 pts: 0.971000 pos: 292435 size: 27834
+ret: 0         st: 0 flags:1 dts: 0.971000 pts: 0.971000 pos: 292346 size: 27834
 ret: 0         st: 0 flags:1  ts:-0.222000
-ret: 0         st: 0 flags:1 dts: 0.011000 pts: 0.011000 pos:   1019 size: 27837
+ret: 0         st: 0 flags:1 dts: 0.011000 pts: 0.011000 pos:    930 size: 27837
 ret:-1         st: 1 flags:0  ts: 2.672000
 ret: 0         st: 1 flags:1  ts: 1.566000
-ret: 0         st: 1 flags:1 dts: 0.993000 pts: 0.993000 pos: 320276 size:   209
+ret: 0         st: 1 flags:1 dts: 0.993000 pts: 0.993000 pos: 320187 size:   209
 ret: 0         st:-1 flags:0  ts: 0.460008
-ret: 0         st: 0 flags:1 dts: 0.491000 pts: 0.491000 pos: 146987 size: 27925
+ret: 0         st: 0 flags:1 dts: 0.491000 pts: 0.491000 pos: 146898 size: 27925
 ret: 0         st:-1 flags:1  ts:-0.645825
-ret: 0         st: 0 flags:1 dts: 0.011000 pts: 0.011000 pos:   1019 size: 27837
+ret: 0         st: 0 flags:1 dts: 0.011000 pts: 0.011000 pos:    930 size: 27837