Nvidia NVENC configuration

- configuration
  - nvenc_preset
  - nvenc_delay
  - nvenc_zerolatency
- documentation

This is minimum to have control over encoder and minimize latency.

To minimize latency:
- set preset to ll, llhq or llhp
- set nvenc_delay to -1 (maps to 0)
- set nvenc_zerolatency to 1

Closes #37

README.md

@@ -118,7 +118,9 @@ There are just 4 functions and 3 user-visible data types:
 ```C
 	struct hve_config hardware_config = {WIDTH, HEIGHT, INPUT_WIDTH, INPUT_HEIGHT, FRAMERATE,
 	                                     DEVICE, ENCODER, PIXEL_FORMAT, PROFILE, BFRAMES,
-	                                     BITRATE, QP, GOP_SIZE, COMPRESSION_LEVEL, VAAPI_LOW_POWER};
+	                                     BITRATE, QP, GOP_SIZE, COMPRESSION_LEVEL,
+	                                     VAAPI_LOW_POWER
+	                                     NVENC_PRESET, NVENC_DELAY, NVENC_ZEROLATENCY};
 
 	struct hve *hardware_encoder=hve_init(&hardware_config);
 	struct hve_frame frame = { 0 };

examples/hve_encode_raw_h264.c

@@ -28,8 +28,11 @@ const int BFRAMES=0; //max_b_frames, set to 0 to minimize latency, non-zero to m
 const int BITRATE=0; //average bitrate in VBR mode (bit_rate != 0 and qp == 0)
 const int QP=0; //quantization parameter in CQP mode (qp != 0 and bit_rate == 0)
 const int GOP_SIZE=0; //group of pictures size, 0 for default (determines keyframe period)
-const int COMPRESSION_LEVEL=0; //speed-quality tradeoff, 0 for default, 1 for the highest quality, 7 for the fastest
+const int COMPRESSION_LEVEL=0; //encoder/codec dependent, 0 for default, for VAAPI 1-7 speed-quality tradeoff, 1 highest quality, 7 fastest
 const int VAAPI_LOW_POWER=0; //alternative VAAPI limited low-power encoding path if non-zero
+const char *NVENC_PRESET=NULL; //NVENC and codec specific, NULL / "" or like "default", "slow", "medium", "fast", "hp", "hq", "bd", "ll", "llhq", "llhp", "lossless", "losslesshp"
+const int NVENC_DELAY=0; //NVENC specific delay of frame output, 0 for default, -1 for 0 or positive value, set -1 to minimize latency
+const int NVENC_ZEROLATENCY=0; //NVENC specific no reordering delay if non-zero, enable to minimize latency
 
 int encoding_loop(struct hve *hardware_encoder, FILE *output_file);
 int process_user_input(int argc, char* argv[]);
@@ -45,7 +48,10 @@ int main(int argc, char* argv[])
 	//prepare library data
 	struct hve_config hardware_config = {WIDTH, HEIGHT, INPUT_WIDTH, INPUT_HEIGHT, FRAMERATE,
 	                                     DEVICE, ENCODER, PIXEL_FORMAT, PROFILE, BFRAMES,
-	                                     BITRATE, QP, GOP_SIZE, COMPRESSION_LEVEL, VAAPI_LOW_POWER};
+	                                     BITRATE, QP, GOP_SIZE, COMPRESSION_LEVEL,
+	                                     VAAPI_LOW_POWER,
+	                                     NVENC_PRESET, NVENC_DELAY, NVENC_ZEROLATENCY};
+
 	struct hve *hardware_encoder;
 
 	//prepare file for raw H.264 output

examples/hve_encode_raw_hevc10.c

@@ -28,8 +28,11 @@ const int BFRAMES=0; //max_b_frames, set to 0 to minimize latency, non-zero to m
 const int BITRATE=0; //average bitrate in VBR mode (bit_rate != 0 and qp == 0)
 const int QP=0; //quantization parameter in CQP mode (qp != 0 and bit_rate == 0)
 const int GOP_SIZE=0; //group of pictures size, 0 for default (determines keyframe period)
-const int COMPRESSION_LEVEL=0; //speed-quality tradeoff, 0 for default, 1 for the highest quality, 7 for the fastest
+const int COMPRESSION_LEVEL=0; //encoder/codec dependent, 0 for default, for VAAPI 1-7 speed-quality tradeoff, 1 highest quality, 7 fastest
 const int VAAPI_LOW_POWER=0; //alternative VAAPI limited low-power encoding path if non-zero
+const char *NVENC_PRESET=NULL; //NVENC and codec specific, NULL / "" or like "default", "slow", "medium", "fast", "hp", "hq", "bd", "ll", "llhq", "llhp", "lossless", "losslesshp"
+const int NVENC_DELAY=0; //NVENC specific delay of frame output, 0 for default, -1 for 0 or positive value, set -1 to minimize latency
+const int NVENC_ZEROLATENCY=0; //NVENC specific no reordering delay if non-zero, enable to minimize latency
 
 int encoding_loop(struct hve *hardware_encoder, FILE *output_file);
 int process_user_input(int argc, char* argv[]);
@@ -45,7 +48,9 @@ int main(int argc, char* argv[])
 	//prepare library data
 	struct hve_config hardware_config = {WIDTH, HEIGHT, INPUT_WIDTH, INPUT_HEIGHT, FRAMERATE,
 	                                     DEVICE, ENCODER, PIXEL_FORMAT, PROFILE, BFRAMES,
-	                                     BITRATE, QP, GOP_SIZE, COMPRESSION_LEVEL, VAAPI_LOW_POWER};
+	                                     BITRATE, QP, GOP_SIZE, COMPRESSION_LEVEL,
+	                                     VAAPI_LOW_POWER,
+	                                     NVENC_PRESET, NVENC_DELAY, NVENC_ZEROLATENCY};
 	struct hve *hardware_encoder;
 
 	//prepare file for raw HEVC output

hve.c

@@ -128,12 +128,21 @@ struct hve *hve_init(const struct hve_config *config)
 
 	AVDictionary *opts = NULL;
 
-	if(config->qp && av_dict_set_int(&opts, "qp", config->qp, 0) < 0)
+	if(config->qp && (av_dict_set_int(&opts, "qp", config->qp, 0) < 0))
 		return hve_close_and_return_null(h, "failed to initialize option dictionary (qp)");
 
-	if(config->vaapi_low_power && av_dict_set_int(&opts, "low_power", config->vaapi_low_power != 0, 0) < 0)
+	if(config->vaapi_low_power && (av_dict_set_int(&opts, "low_power", config->vaapi_low_power != 0, 0) < 0))
 		return hve_close_and_return_null(h, "failed to initialize option dictionary (low_power)");
 
+	if(config->nvenc_preset && config->nvenc_preset[0] != '\0' && (av_dict_set(&opts, "preset", config->nvenc_preset, 0) < 0))
+		return hve_close_and_return_null(h, "failed to initialize option dictionary (NVENC preset)");
+
+	if(config->nvenc_delay && (av_dict_set_int(&opts, "delay", (config->nvenc_delay > 0) ? config->nvenc_delay : 0, 0) < 0))
+		return hve_close_and_return_null(h, "failed to initialize option dictionary (NVENC delay)");
+
+	if(config->nvenc_zerolatency && (av_dict_set_int(&opts, "zerolatency", config->nvenc_zerolatency != 0 , 0) < 0))
+		return hve_close_and_return_null(h, "failed to initialize option dictionary (NVENC zerolatency)");
+
 	if((err = avcodec_open2(h->avctx, codec, &opts)) < 0)
 	{
 		av_dict_free(&opts);

hve.h

@@ -156,6 +156,24 @@ struct hve;
  * For the details on loading HuC see:
  * <a href="https://github.com/bmegli/hardware-video-encoder/wiki/GuC-and-HuC">Loading GuC and HuC</a>
  *
+ * The nvenc_preset is encoding preset to use, may be codec specific.
+ *
+ * The default is medium ("default", "" or NULL string)
+ *
+ * Typicall values: "default", "slow", "medium", "fast", "hp", "hq", "bd", "ll", "llhq", "llhp", "lossless", "losslesshp"
+ *
+ * You may check available presets (H.264 example)
+ * @code
+ * ffmpeg -h encoder=h264_nvenc -hide_banner
+ * @endcode
+ *
+ * The nvenc_delay is delay for frame output by given amount of frames.
+ * 0 leaves defaults (which is INT_MAX in FFmpeg nvenc), -1 sets 0.
+ * Set to -1 (maps to 0) if you explicitly need low latency.
+ *
+ * The nvenc_zerolatency is NVENC specific for no reordering delay.
+ * Set to non-zero if you need low latency.
+ *
  * @see hve_init
  */
 struct hve_config
@@ -175,6 +193,9 @@ struct hve_config
 	int gop_size; //!<  group of pictures size, 0 for default, -1 for intra only
 	int compression_level; //!< encoder/codec dependent, 0 for default, for VAAPI 1-7 speed-quality tradeoff, 1 highest quality, 7 fastest
 	int vaapi_low_power; //!< VAAPI specific alternative limited low-power encoding if non-zero
+	const char *nvenc_preset; //!< NVENC and codec specific, NULL / "" or like "default", "slow", "medium", "fast", "hp", "hq", "bd", "ll", "llhq", "llhp", "lossless", "losslesshp"
+	int nvenc_delay; //NVENC specific delay of frame output, 0 for default, -1 for 0 or positive value, set -1 to minimize latency
+	int nvenc_zerolatency; //NVENC specific no reordering delay if non-zero, enable to minimize latency
 };
 
 /**