[FFmpeg-cvslog] avcodec/mpeg4video: Make initializing RLTable thread-safe

[Andreas Rheinhardt]

ffmpeg | branch: master | Andreas Rheinhardt <andreas.rheinhardt at gmail.com> | Thu Dec 10 04:32:17 2020 +0100| [d99707b42a55b2fcfc17b8c9bf3f38c1879dbaa7] | committer: Andreas Rheinhardt

avcodec/mpeg4video: Make initializing RLTable thread-safe

Up until now the RLTable ff_mpeg4_rl_intra was initialized by both mpeg4
decoder and encoder (except the VLCs that are only used by the decoder).
This is an obstacle to making these codecs init-threadsafe, so move
initializing this to a single function that is guarded by a dedicated
AVOnce.

Reviewed-by: Anton Khirnov <anton at khirnov.net>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=d99707b42a55b2fcfc17b8c9bf3f38c1879dbaa7
---

 libavcodec/mpeg4video.c    | 14 +++++++++++++-
 libavcodec/mpeg4video.h    |  3 +--
 libavcodec/mpeg4videodec.c |  8 +++++---
 libavcodec/mpeg4videoenc.c |  2 +-
 4 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/libavcodec/mpeg4video.c b/libavcodec/mpeg4video.c
index 2aaa9f734c..ffeaf822b2 100644
--- a/libavcodec/mpeg4video.c
+++ b/libavcodec/mpeg4video.c
@@ -20,12 +20,24 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#include "libavutil/thread.h"
+
 #include "mpegutils.h"
 #include "mpegvideo.h"
 #include "mpeg4video.h"
 #include "mpeg4data.h"
 
-uint8_t ff_mpeg4_static_rl_table_store[3][2][2 * MAX_RUN + MAX_LEVEL + 3];
+static av_cold void mpeg4_init_rl_intra(void)
+{
+    static uint8_t mpeg4_rl_intra_table[2][2 * MAX_RUN + MAX_LEVEL + 3];
+    ff_rl_init(&ff_mpeg4_rl_intra, mpeg4_rl_intra_table);
+}
+
+av_cold void ff_mpeg4_init_rl_intra(void)
+{
+    static AVOnce init_static_once = AV_ONCE_INIT;
+    ff_thread_once(&init_static_once, mpeg4_init_rl_intra);
+}
 
 int ff_mpeg4_get_video_packet_prefix_length(MpegEncContext *s)
 {
diff --git a/libavcodec/mpeg4video.h b/libavcodec/mpeg4video.h
index e919db87a5..3db6f85153 100644
--- a/libavcodec/mpeg4video.h
+++ b/libavcodec/mpeg4video.h
@@ -129,6 +129,7 @@ extern const int8_t ff_mpeg4_intra_level[102];
 extern const int8_t ff_mpeg4_intra_run[102];
 
 extern RLTable ff_mpeg4_rl_intra;
+void ff_mpeg4_init_rl_intra(void);
 
 /* Note this is identical to the intra rvlc except that it is reordered. */
 extern RLTable ff_rvlc_rl_inter;
@@ -180,8 +181,6 @@ int ff_mpeg4_frame_end(AVCodecContext *avctx, const uint8_t *buf, int buf_size);
  */
 int ff_mpeg4_set_direct_mv(MpegEncContext *s, int mx, int my);
 
-extern uint8_t ff_mpeg4_static_rl_table_store[3][2][2 * MAX_RUN + MAX_LEVEL + 3];
-
 #if 0 //3IV1 is quite rare and it slows things down a tiny bit
 #define IS_3IV1 s->codec_tag == AV_RL32("3IV1")
 #else
diff --git a/libavcodec/mpeg4videodec.c b/libavcodec/mpeg4videodec.c
index de66fe8b83..fc76485dbe 100644
--- a/libavcodec/mpeg4videodec.c
+++ b/libavcodec/mpeg4videodec.c
@@ -3378,9 +3378,11 @@ av_cold void ff_mpeg4videodec_static_init(void) {
     static int done = 0;
 
     if (!done) {
-        ff_rl_init(&ff_mpeg4_rl_intra, ff_mpeg4_static_rl_table_store[0]);
-        ff_rl_init(&ff_rvlc_rl_inter, ff_mpeg4_static_rl_table_store[1]);
-        ff_rl_init(&ff_rvlc_rl_intra, ff_mpeg4_static_rl_table_store[2]);
+        static uint8_t mpeg4_rvlc_rl_tables[2][2][2 * MAX_RUN + MAX_LEVEL + 3];
+
+        ff_mpeg4_init_rl_intra();
+        ff_rl_init(&ff_rvlc_rl_inter, mpeg4_rvlc_rl_tables[0]);
+        ff_rl_init(&ff_rvlc_rl_intra, mpeg4_rvlc_rl_tables[1]);
         INIT_FIRST_VLC_RL(ff_mpeg4_rl_intra, 554);
         INIT_VLC_RL(ff_rvlc_rl_inter, 1072);
         INIT_FIRST_VLC_RL(ff_rvlc_rl_intra, 1072);
diff --git a/libavcodec/mpeg4videoenc.c b/libavcodec/mpeg4videoenc.c
index 7145bfe8ce..4593fe6096 100644
--- a/libavcodec/mpeg4videoenc.c
+++ b/libavcodec/mpeg4videoenc.c
@@ -1285,7 +1285,7 @@ static av_cold int encode_init(AVCodecContext *avctx)
 
         init_uni_dc_tab();
 
-        ff_rl_init(&ff_mpeg4_rl_intra, ff_mpeg4_static_rl_table_store[0]);
+        ff_mpeg4_init_rl_intra();
 
         init_uni_mpeg4_rl_tab(&ff_mpeg4_rl_intra, uni_mpeg4_intra_rl_bits, uni_mpeg4_intra_rl_len);
         init_uni_mpeg4_rl_tab(&ff_h263_rl_inter, uni_mpeg4_inter_rl_bits, uni_mpeg4_inter_rl_len);