lavc: Introduce AVCodec internal capabilities

This field is designed for marking codec properties useful to lavc internals.
Two internal capabilities are added:
 - FF_CODEC_CAP_INIT_THREADSAFE: codec can be opened without locks;
 - FF_CODEC_CAP_INIT_CLEANUP: codec frees memory if initialization fails.

libavcodec/avcodec.h

@@ -2924,6 +2924,11 @@ typedef struct AVCodec {
      * Will be called when seeking
      */
     void (*flush)(AVCodecContext *);
+    /**
+     * Internal codec capabilities.
+     * See FF_CODEC_CAP_* in internal.h
+     */
+    int caps_internal;
 } AVCodec;
 
 /**

libavcodec/internal.h

@@ -33,6 +33,16 @@
 #include "avcodec.h"
 #include "config.h"
 
+/**
+ * Codec is thread safe.
+ */
+#define FF_CODEC_CAP_INIT_THREADSAFE        (1 << 0)
+/**
+ * Codec cleans up memory on init failure.
+ */
+#define FF_CODEC_CAP_INIT_CLEANUP           (1 << 1)
+
+
 #define FF_SANE_NB_CHANNELS 63U
 
 #define FF_SIGNBIT(x) (x >> CHAR_BIT * sizeof(x) - 1)

libavcodec/utils.c

@@ -1049,7 +1049,8 @@ int attribute_align_arg avcodec_open2(AVCodecContext *avctx, const AVCodec *code
     }
 
     entangled_thread_counter++;
-    if (entangled_thread_counter != 1) {
+    if (entangled_thread_counter != 1 &&
+        !(codec->caps_internal & FF_CODEC_CAP_INIT_THREADSAFE)) {
         av_log(avctx, AV_LOG_ERROR,
                "Insufficient thread locking. At least %d threads are "
                "calling avcodec_open2() at the same time right now.\n",
@@ -1286,6 +1287,10 @@ end:
 
     return ret;
 free_and_end:
+    if (avctx->codec &&
+        (avctx->codec->caps_internal & FF_CODEC_CAP_INIT_CLEANUP))
+        avctx->codec->close(avctx);
+
     av_dict_free(&tmp);
     av_freep(&avctx->priv_data);
     if (avctx->internal) {