Update: I can now see this below firmware was released in 2020-7-13, so it isn't new!
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Wondering why then my HikConnect lag issue has resolved itself this week.
My system is set to auto-update so the NVR is now up to v4.40.015 build 200616.
Not read the notes (if any) but whatever was in the updates in the last week has resolved my problem of lagging playback through HikConnect app. I was going to raise here to see if others noticed that playback would freeze through the app (and with events playback). Footage would freeze 10-15 seconds at a time, play for a few seconds than freeze again. I put it down to using H.265+on all my streams and my phone not handling the decode. Not it was the same on other phones I tried Android and Iphone).
Testing this morning, playback for events and normal playback is mostly fluid, maybe with one or two 1 second delays but very much acceptable compared to before.
LiveView still hangs when using HD primary stream (4mp, H.265+ cameras) but I think this was the case previously also. This is easy to deal with by switching to second stream ("Basic" in the app). The playback freezing was a nightmare so will keep testing and I'm hopeful it fully resolved.
Anyone else spotted this?