lavc: add new unsafe_output hwaccel_flag

doc/APIchanges

@@ -14,6 +14,9 @@ libavutil:     2021-04-27
 
 API changes, most recent first:
 
+2022-12-xx - xxxxxxxxxx - lavc 59.55.100 - avcodec.h
+  Add AV_HWACCEL_FLAG_UNSAFE_OUTPUT.
+
 2022-11-xx - xxxxxxxxxx - lavu 57.43.100 - tx.h
   Add AV_TX_FLOAT_DCT, AV_TX_DOUBLE_DCT and AV_TX_INT32_DCT.
 

libavcodec/avcodec.h

@@ -2253,6 +2253,22 @@ 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)
+
 /**
  * @}
  */

libavcodec/options_table.h

@@ -399,6 +399,7 @@ static const AVOption avcodec_options[] = {
 {"ignore_level", "ignore level even if the codec level used is unknown or higher than the maximum supported level reported by the hardware driver", 0, AV_OPT_TYPE_CONST, { .i64 = AV_HWACCEL_FLAG_IGNORE_LEVEL }, INT_MIN, INT_MAX, V | D, "hwaccel_flags" },
 {"allow_high_depth", "allow to output YUV pixel formats with a different chroma sampling than 4:2:0 and/or other than 8 bits per component", 0, AV_OPT_TYPE_CONST, {.i64 = AV_HWACCEL_FLAG_ALLOW_HIGH_DEPTH }, INT_MIN, INT_MAX, V | D, "hwaccel_flags"},
 {"allow_profile_mismatch", "attempt to decode anyway if HW accelerated decoder's supported profiles do not exactly match the stream", 0, AV_OPT_TYPE_CONST, {.i64 = AV_HWACCEL_FLAG_ALLOW_PROFILE_MISMATCH }, INT_MIN, INT_MAX, V | D, "hwaccel_flags"},
+{"unsafe_output", "allow potentially unsafe hwaccel frame output that might require special care to process successfully", 0, AV_OPT_TYPE_CONST, {.i64 = AV_HWACCEL_FLAG_UNSAFE_OUTPUT }, INT_MIN, INT_MAX, V | D, "hwaccel_flags"},
 {"extra_hw_frames", "Number of extra hardware frames to allocate for the user", OFFSET(extra_hw_frames), AV_OPT_TYPE_INT, { .i64 = -1 }, -1, INT_MAX, V|D },
 {"discard_damaged_percentage", "Percentage of damaged samples to discard a frame", OFFSET(discard_damaged_percentage), AV_OPT_TYPE_INT, {.i64 = 95 }, 0, 100, V|D },
 {NULL},

libavcodec/version.h

@@ -29,8 +29,8 @@
 
 #include "version_major.h"
 
-#define LIBAVCODEC_VERSION_MINOR  54
-#define LIBAVCODEC_VERSION_MICRO 101
+#define LIBAVCODEC_VERSION_MINOR  55
+#define LIBAVCODEC_VERSION_MICRO 100
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
                                                LIBAVCODEC_VERSION_MINOR, \