h2645_parse: allow partial escaping

This ports the fix from 033a533 to the new parser module in prepartion
of using it for the h264 decoder.

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>

libavcodec/h2645_parse.c

@@ -38,7 +38,7 @@ int ff_h2645_extract_rbsp(const uint8_t *src, int length,
     nal->skipped_bytes = 0;
 #define STARTCODE_TEST                                                  \
         if (i + 2 < length && src[i + 1] == 0 && src[i + 2] <= 3) {     \
-            if (src[i + 2] != 3) {                                      \
+            if (src[i + 2] != 3 && src[i + 2] != 0) {                   \
                 /* startcode, so we must be past the end */             \
                 length = i;                                             \
             }                                                           \
@@ -103,7 +103,7 @@ int ff_h2645_extract_rbsp(const uint8_t *src, int length,
         if (src[si + 2] > 3) {
             dst[di++] = src[si++];
             dst[di++] = src[si++];
-        } else if (src[si] == 0 && src[si + 1] == 0) {
+        } else if (src[si] == 0 && src[si + 1] == 0 && src[si + 2] != 0) {
             if (src[si + 2] == 3) { // escape
                 dst[di++] = 0;
                 dst[di++] = 0;