avcodec/h261dec: Make decoder init-threadsafe

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

libavcodec/h261dec.c

@@ -26,6 +26,7 @@
  */
 
 #include "libavutil/avassert.h"
+#include "libavutil/thread.h"
 #include "avcodec.h"
 #include "mpeg_er.h"
 #include "mpegutils.h"
@@ -47,12 +48,8 @@ static VLC h261_mtype_vlc;
 static VLC h261_mv_vlc;
 static VLC h261_cbp_vlc;
 
-static av_cold void h261_decode_init_vlc(H261Context *h)
+static av_cold void h261_decode_init_static(void)
 {
-    static int done = 0;
-
-    if (!done) {
-        done = 1;
         INIT_VLC_STATIC(&h261_mba_vlc, H261_MBA_VLC_BITS, 35,
                         ff_h261_mba_bits, 1, 1,
                         ff_h261_mba_code, 1, 1, 662);
@@ -66,11 +63,11 @@ static av_cold void h261_decode_init_vlc(H261Context *h)
                         &ff_h261_cbp_tab[0][1], 2, 1,
                         &ff_h261_cbp_tab[0][0], 2, 1, 512);
         INIT_FIRST_VLC_RL(ff_h261_rl_tcoeff, 552);
-    }
 }
 
 static av_cold int h261_decode_init(AVCodecContext *avctx)
 {
+    static AVOnce init_static_once = AV_ONCE_INIT;
     H261Context *h          = avctx->priv_data;
     MpegEncContext *const s = &h->s;
 
@@ -81,10 +78,10 @@ static av_cold int h261_decode_init(AVCodecContext *avctx)
     s->low_delay   = 1;
     avctx->pix_fmt = AV_PIX_FMT_YUV420P;
 
-    h261_decode_init_vlc(h);
-
     h->gob_start_code_skipped = 0;
 
+    ff_thread_once(&init_static_once, h261_decode_init_static);
+
     return 0;
 }
 
@@ -684,6 +681,6 @@ AVCodec ff_h261_decoder = {
     .close          = h261_decode_end,
     .decode         = h261_decode_frame,
     .capabilities   = AV_CODEC_CAP_DR1,
-    .caps_internal  = FF_CODEC_CAP_INIT_CLEANUP,
+    .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE | FF_CODEC_CAP_INIT_CLEANUP,
     .max_lowres     = 3,
 };