lavc NVENC: use param lavc-rc-buffer-size-factor if set

+ hint

Author: MartinPulec

src/video_compress/libavcodec.cpp

@@ -106,7 +106,7 @@ static constexpr const int DEFAULT_GOP_SIZE = 20;
 static constexpr int DEFAULT_SLICE_COUNT = 32;
 static constexpr string_view DONT_SET_PRESET = "dont_set_preset";
 
-#define DEFAULT_RC_BUF_SIZE_FACTOR 2.5
+#define DEFAULT_X26X_RC_BUF_SIZE_FACTOR 2.5
 
 namespace {
 
@@ -1761,7 +1761,7 @@ static void configure_amf([[maybe_unused]] AVCodecContext *codec_ctx, [[maybe_un
 ADD_TO_PARAM("lavc-h264-interlaced-dct", "* lavc-h264-interlaced-dct\n"
                  "  Use interlaced DCT for H.264\n");
 ADD_TO_PARAM("lavc-rc-buffer-size-factor", "* lavc-rc-buffer-size-factor=<val>\n"
-                 "  Multiplier how much can individual frame overshot average size (default: " TOSTRING(DEFAULT_RC_BUF_SIZE_FACTOR) ").\n");
+                 "  Multiplier how much can individual frame overshot average size (default x264/5: " TOSTRING(DEFAULT_X26X_RC_BUF_SIZE_FACTOR) ", nvenc: 1).\n");
 static void configure_x264_x265(AVCodecContext *codec_ctx, struct setparam_param *param)
 {
         const char *tune = codec_ctx->codec->id == AV_CODEC_ID_H264 ? "zerolatency,fastdecode" : "zerolatency"; // x265 supports only single tune parameter
@@ -1771,7 +1771,7 @@ static void configure_x264_x265(AVCodecContext *codec_ctx, struct setparam_param
         codec_ctx->rc_max_rate = codec_ctx->bit_rate;
         //codec_ctx->rc_min_rate = s->codec_ctx->bit_rate / 4 * 3;
         //codec_ctx->rc_buffer_aggressivity = 1.0;
-        double lavc_rc_buffer_size_factor = DEFAULT_RC_BUF_SIZE_FACTOR;
+        double lavc_rc_buffer_size_factor = DEFAULT_X26X_RC_BUF_SIZE_FACTOR;
         if (const char *val = get_commandline_param("lavc-rc-buffer-size-factor")) {
                 lavc_rc_buffer_size_factor = stof(val);
         }
@@ -1890,6 +1890,12 @@ static void configure_nvenc(AVCodecContext *codec_ctx, struct setparam_param *pa
         check_av_opt_set<const char *>(codec_ctx->priv_data, "b_ref_mode", "disabled", 0);
         codec_ctx->rc_max_rate = codec_ctx->bit_rate;
         codec_ctx->rc_buffer_size = codec_ctx->rc_max_rate / param->desc.fps;
+        if (const char *val = get_commandline_param("lavc-rc-buffer-size-factor")) {
+                codec_ctx->rc_buffer_size *= stof(val);
+        } else {
+                log_msg(LOG_LEVEL_WARNING, MOD_NAME "To reduce NVENC pulsation, you can try \"--param lavc-rc-buffer-size-factor=0\""
+                                       " or a small number. 0 or higher value (than default 1) may cause frame drops on receiver.\n");
+        }
 }
 
 static void configure_svt(AVCodecContext *codec_ctx, struct setparam_param *param)