[FFmpeg-user] hevc_nvenc pts < dts error on some time_bases

[Louis Letourneau]

Using
ffmpeg version 7.0.2 Copyright (c) 2000-2024 the FFmpeg developers

I keep getting this error:
[mp4 @ 0x60f656ba95c0] pts (1000) < dts (1997) in stream 0

If in my C++ code I try to encode images in timebase 1/60000, framerate
60000/1001 or 60000/1000

I modified the doc/examples/mux.c to force hevc_nvenc and timebases (patch
attached)

If I use 1/60 timbase and 60/1 frame_rate, it all works fine.

ffmpeg command line seems to be able to do it at 59.94 with -vf fps or
forcing with -r

Using libx264 or libx265 works fine.

Any ideas?

Thanks
Louis

--- ../f/ffmpeg-7.0.2/doc/examples/mux.c        2024-08-02 18:55:25.000000000 
-0400
+++ doc/examples/mux.c  2025-01-13 21:25:46.914932469 -0500
@@ -44,7 +44,6 @@
 #include <libswresample/swresample.h>
 
 #define STREAM_DURATION   10.0
-#define STREAM_FRAME_RATE 25 /* 25 images/s */
 #define STREAM_PIX_FMT    AV_PIX_FMT_YUV420P /* default pix_fmt */
 
 #define SCALE_FLAGS SWS_BICUBIC
@@ -131,6 +130,10 @@
 
     /* find the encoder */
     *codec = avcodec_find_encoder(codec_id);
+    if((*codec)->type == AVMEDIA_TYPE_VIDEO) {
+        *codec = avcodec_find_encoder_by_name("hevc_nvenc");
+        codec_id = (*codec)->id;
+    }
     if (!(*codec)) {
         fprintf(stderr, "Could not find encoder for '%s'\n",
                 avcodec_get_name(codec_id));
@@ -184,7 +187,7 @@
          * of which frame timestamps are represented. For fixed-fps content,
          * timebase should be 1/framerate and timestamp increments should be
          * identical to 1. */
-        ost->st->time_base = (AVRational){ 1, STREAM_FRAME_RATE };
+        ost->st->time_base = (AVRational){ 1, 60000 };
         c->time_base       = ost->st->time_base;
 
         c->gop_size      = 12; /* emit one intra frame every twelve frames at 
most */
@@ -504,7 +507,8 @@
         fill_yuv_image(ost->frame, ost->next_pts, c->width, c->height);
     }
 
-    ost->frame->pts = ost->next_pts++;
+    ost->frame->pts = ost->next_pts;
+    ost->next_pts += 1001;
 
     return ost->frame;
 }

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