Audio Slowly Desynchronizing When Segmenting

Question

I use ffmpeg's ability to segment video while I record so I can record constantly without my hard drive filling up.

It works really well, expect the audio desynchronizes from the video when the file segments. The video seems to be uninterrupted but I can actually hear a tiny jump in the audio when I join segments later on. One would think that ffmpeg would store packets in a queue during segmentation so nothing is lost but that doesn't seem to be the case... Any way I could force it to do something like that?

Here is my current block:

ffmpeg -y -thread_queue_size 5096 -f dshow -video_size 3440x1440 -rtbufsize 2147.48M -framerate 100 -pixel_format nv12 ^
-itsoffset 00:00:00.012 -i video="Video (00 Pro Capture HDMI 4K+)" -thread_queue_size 5096 -guess_layout_max 0 -f dshow ^
-rtbufsize 2147.48M -i audio="SPDIF/ADAT (1+2) (RME Fireface UC)" -map 0:0,1:0 -map 1:0 -c:v h264_nvenc -preset: llhp ^
-pix_fmt nv12 -b:v 250M -minrate 250M -maxrate 250M -bufsize 250M -b:a 384k -ac 2 -r 100 -vsync 1 ^
-max_muxing_queue_size 5096 -segment_time 600 -segment_wrap 9 -f segment C:\Users\djcim\Videos\PC\PC\PC%02d.mp4 

I am delaying the video stream because right out the gate it's a little bit ahead of the audio.

PS: aresample or async seem to have no effect or at least not a desirable one.

Answer 1

Using -reset_timestamps in conjunction with encoding .ts instead of .mp4 has mostly solved this issue. -reset_timestamps does not appear to work when encoding .mp4, not sure why, maybe a bug?

I say mostly because audio still drifts around a frame after the first segment, but not exponentially. I find audio de-synced by one frame acceptable. Although I should mention now when I try to concat the clips back together I have audio drift issues, not always, but sometimes. Using aresample=async=250 fixes the drift after concat but you can hear the audio stretch a bit when doing so. Can't expect everything to work perfectly.

ffmpeg - y -thread_queue_size 9999 -indexmem 9999 -guess_layout_max 0 -f dshow -video_size 3440x1440 -rtbufsize 2147.48M ^
-framerate 200 -pixel_format nv12 -i video="Video (00 Pro Capture HDMI 4K+)":audio="SPDIF/ADAT (1+2) (RME Fireface UC)" ^
-map 0:0,0:1 -map 0:1 -flags +cgop -force_key_frames expr:gte(t,n_forced*2) -c:v h264_nvenc -preset: llhp -pix_fmt nv12 ^
-b:v 250M -minrate 250M -maxrate 250M -bufsize 250M -c:a aac -ar 44100 -b:a 384k -ac 2 -r 100 ^
-af "atrim=0.038, asetpts=PTS-STARTPTS, aresample=async=250" -vsync 1 -ss 00:00:01.096 -max_muxing_queue_size 9999 ^
-f segment -segment_time 600 -segment_wrap 9 -reset_timestamps 1 C:\Users\djcim\Videos\PC\PC\PC%02d.ts