lavc: add new unsafe_output hwaccel_flag

1 files changed, 16 insertions, 0 deletions

diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index 3edd8e2636..0ac581d660 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -2254,6 +2254,22 @@ typedef struct AVHWAccel {
 #define AV_HWACCEL_FLAG_ALLOW_PROFILE_MISMATCH (1 << 2)
 
 /**
+ * Some hardware decoders (namely nvdec) can either output direct decoder
+ * surfaces, or make an on-device copy and return said copy.
+ * There is a hard limit on how many decoder surfaces there can be, and it
+ * cannot be accurately guessed ahead of time.
+ * For some processing chains, this can be okay, but others will run into the
+ * limit and in turn produce very confusing errors that require fine tuning of
+ * more or less obscure options by the user, or in extreme cases cannot be
+ * resolved at all without inserting an avfilter that forces a copy.
+ *
+ * Thus, the hwaccel will by default make a copy for safety and resilience.
+ * If a users really wants to minimize the amount of copies, they can set this
+ * flag and ensure their processing chain does not exhaust the surface pool.
+ */
+#define AV_HWACCEL_FLAG_UNSAFE_OUTPUT (1 << 3)
+
+/**
  * @}
  */