vcomp/lavc: h264_nvenc: fix pulsation w intra-refr

Avoid pulsation with inra-refresh by repeating the missing SPS/PPS with
header inseter.

Unfortunately this is doesn't work well with HEVC because it seems that
the NVIDIA encoder keeps the reference almost forever in specific cases,
eg. `testcard:patt=text`. However, it _may_ work under some circumstances.

Author: MartinPulec

.github/scripts/Linux/ffmpeg-patches/0001-NVENC_INFINITE_GOPLENGTH-is-useless-for-UltraGrid-up.patch

@@ -24,14 +24,6 @@ diff --git a/libavcodec/nvenc.c b/libavcodec/nvenc.c
 index 0b6417674e..70adc26f08 100644
 --- a/libavcodec/nvenc.c
 +++ b/libavcodec/nvenc.c
-@@ -1173,7 +1173,6 @@ static av_cold int nvenc_setup_h264_config(AVCodecContext *avctx)
-         h264->enableIntraRefresh = 1;
-         h264->intraRefreshPeriod = cc->gopLength;
-         h264->intraRefreshCnt = cc->gopLength - 1;
--        cc->gopLength = NVENC_INFINITE_GOPLENGTH;
- #ifdef NVENC_HAVE_SINGLE_SLICE_INTRA_REFRESH
-         h264->singleSliceIntraRefresh = ctx->single_slice_intra_refresh;
- #endif
 @@ -1294,7 +1293,6 @@ static av_cold int nvenc_setup_hevc_config(AVCodecContext *avctx)
          hevc->enableIntraRefresh = 1;
          hevc->intraRefreshPeriod = cc->gopLength;

src/video_compress/libavcodec.cpp

@@ -1997,16 +1997,30 @@ static void configure_nvenc(AVCodecContext *codec_ctx, struct setparam_param *pa
         }
 
         check_av_opt_set(codec_ctx->priv_data, "forced-idr", 1);
+
+        const bool h264 = codec_ctx->codec_id == AV_CODEC_ID_H264;
 #ifdef PATCHED_FF_NVENC_NO_INFINITE_GOP
         const bool patched_ff = true;
 #else
         const bool patched_ff = false;
-        if (param->periodic_intra != 0) {
+        if (!h264 && param->periodic_intra != 0) {
                 LOG(LOG_LEVEL_WARNING) << MOD_NAME "FFmpeg not patched, " << (param->periodic_intra != 1 ? "not " : "") << "enabling Intra Refresh.\n";
         }
 #endif
+        if (h264 && param->periodic_intra != 0) {
+                if (param->header_inserter_req == -1) {
+                        MSG(INFO,
+                            "Auto-enabling header inserter for H.264 when "
+                            "intra-refresh used.\n");
+                        param->header_inserter_req = 1;
+                }
+                param->periodic_intra = 1;
+        }
+        if (!h264 && patched_ff && param->periodic_intra != 0) {
+                param->periodic_intra = 1;
+        }
 
-        if ((patched_ff && param->periodic_intra != 0) || param->periodic_intra == 1) {
+        if (param->periodic_intra == 1) {
                 incomp_feature_warn(INCOMP_INTRA_REFRESH, param->periodic_intra);
                 check_av_opt_set<int>(codec_ctx->priv_data, "intra-refresh", 1);
         }
@@ -2021,10 +2035,10 @@ static void configure_nvenc(AVCodecContext *codec_ctx, struct setparam_param *pa
         double lavc_rc_buffer_size_factor = DEFAULT_NVENC_RC_BUF_SIZE_FACTOR;
         if (const char *val = get_commandline_param("lavc-rc-buffer-size-factor")) {
                 lavc_rc_buffer_size_factor = stof(val);
-        } else {
+        } else if (!h264) {
                 LOG(LOG_LEVEL_WARNING)
                     << MOD_NAME
-                    "To reduce NVENC pulsation, you can try \"--param "
+                    "To reduce NVENC HEVC/AV1 pulsation, you can try \"--param "
                     "lavc-rc-buffer-size-factor=0\""
                     " or a small number. 0 or higher value (than default "
                     << DEFAULT_NVENC_RC_BUF_SIZE_FACTOR