Fix crash on resolution change (issue 2393).

Don't free RBSP tables (containing decoded NAL units) on resolution
change, because we actually need this data to decode the frame after
reiniting (with new resolution). Fixed issue 2393.
Signed-off-by: Janne Grunau <janne-ffmpeg@jannau.net>
(cherry picked from commit 91078926)

libavcodec/h264.c

@@ -614,7 +614,7 @@ static void hl_motion(H264Context *h, uint8_t *dest_y, uint8_t *dest_cb, uint8_t
 }
 
 
-static void free_tables(H264Context *h){
+static void free_tables(H264Context *h, int free_rbsp){
     int i;
     H264Context *hx;
     av_freep(&h->intra4x4_pred_mode);
@@ -637,10 +637,12 @@ static void free_tables(H264Context *h){
         av_freep(&hx->top_borders[1]);
         av_freep(&hx->top_borders[0]);
         av_freep(&hx->s.obmc_scratchpad);
+        if (free_rbsp){
         av_freep(&hx->rbsp_buffer[1]);
         av_freep(&hx->rbsp_buffer[0]);
         hx->rbsp_buffer_size[0] = 0;
         hx->rbsp_buffer_size[1] = 0;
+        }
         if (i) av_freep(&h->thread_context[i]);
     }
 }
@@ -748,7 +750,7 @@ int ff_h264_alloc_tables(H264Context *h){
 
     return 0;
 fail:
-    free_tables(h);
+    free_tables(h, 1);
     return -1;
 }
 
@@ -1776,7 +1778,7 @@ static int decode_slice_header(H264Context *h, H264Context *h0){
             || av_cmp_q(h->sps.sar, s->avctx->sample_aspect_ratio))) {
         if(h != h0)
             return -1;   // width / height changed during parallelized decoding
-        free_tables(h);
+        free_tables(h, 0);
         flush_dpb(s->avctx);
         MPV_common_end(s);
     }
@@ -3331,7 +3333,7 @@ av_cold void ff_h264_free_context(H264Context *h)
 {
     int i;
 
-    free_tables(h); //FIXME cleanup init stuff perhaps
+    free_tables(h, 1); //FIXME cleanup init stuff perhaps
 
     for(i = 0; i < MAX_SPS_COUNT; i++)
         av_freep(h->sps_buffers + i);