Low Bitrate?

[pur1337]

Hello everyone,

Recently joined and have been checking out the Dahua cams. Currently thinking of using 4x IPC-T5442TM-AS as a start paired with Blue Iris and a 7700k based system. Low light performance is a must. Planning on running gigabit lines + poe+ to all cams. Space not an issue, 30+ TB at the house.

I've done some digging on Dahua but have not checked out Hikvison yet. Perhaps I am just looking at the wrong cameras.

Can anyone comment on the low bitrate? I notice the IPC-T5442TM-AS only has 8192kbps. I have seen some set bitrate a touch higher, but not more than 10000 kbps or so. I have some experience with Video editing and Gopros, and this bitrate for the resolution (2688×1520(30fps)) seems quite low. I'd like to see something 4-5x that for the resolution. I took a brief look at 4k cams but the bitrate was not much higher.

 

[sebastiantombs]

Keep in mind that these cameras are for surveillance and not for producing movies.

 

[pur1337]

Keep in mind that these cameras are for surveillance and not for producing movies.

I'm not trying to be hostile, but I would just think the resolution is pointless with such low bitrate. From my perspective, bitrate is far more important than the resolution.

 

[samplenhold]

I took a brief look at 4k cams but the bitrate was not much higher.

You will not get good night performance from 4K cams unless you are willing to pay $15k-$20k.

 

[sebastiantombs]

I don't have your experience level, but I will say that 8192bps on a 4MP camera used in surveillance is fine. The entire industry seems quite happy with it. Also keep in mind the frame rates normally used are in the 10 to 15FPS range with an iframe to match.

 

[samplenhold]

I'm not trying to be hostile, but I would just think the resolution is pointless with such low bitrate. From my perspective, bitrate is far more important than the resolution.

Not taken as hostile. Realize that there is a trade off between bit rate/quality and storage size. You can get 20480 out of it if you try. But I have not ever seen much difference and run all of mine at 8192 and 15 FPS. That is just fine for surveillance. Believe me, everyone here is determined to get the best face shot possible.

 

[wittaj]

And keep in mind that these cameras, although are spec'd and capable of these various parameters, real world testing shows if you try to run these cameras at 30fps and high bitrates that you will max out the CPU in the camera and then the camera bugs out just long enough that you miss something. My car is rated for 6,000RPM redline, but I am not gonna run it in 3rd gear on the highway at 6,000RPM...same with these types of cameras - gotta keep them under rated capacity.

Look at all the threads where people came here with a jitter in the video or IVS missing motion and they were running 30FPS and when people tell them to drop the FPS and they dropped the FPS to 15FPS the camera became stable.

Movies for the big screen are shot at 24FPS, so I don't think we need 30FPS for our phones, tablet, and monitors at home LOL. 15FPS for surveillance is fine.

And as pointed out, if you change bitrate to custom then you can go above 8192...

We here are fanatics about producing the best image possible at night of a perp, so believe us when we say if there was a benefit to more FPS and 20k bitrate, we would all be doing it! We are not going for slow motion effects like one can do with a go-pro either.

 

[tigerwillow1]

I'm not trying to be hostile, but I would just think the resolution is pointless with such low bitrate. From my perspective, bitrate is far more important than the resolution.

I mostly agree with you on this, with the exception from my experimenting the resolution isn't totally pointless. When I run a 2MP and 4MP camera at the same bitrate the resolution on the 4MP camera is somewhat better. At a higher bitrate it improves more. If you need better resolution in only part of the image, ROI can make a big difference. It shows what the camera would be capable of at a higher bitrate than we're allowed to set it to. My 5442s' max bitrate is 20,480 kbps. I don't use the very latest firmware, so don't know if that's a factor.

Just for the heck of it I saved some snaps at 8192 and 20480. With the target greater that 50 feet from the camera I don't see much if any improvement at the higher bitrate. Perhaps the pixel resolution is maxed out. In the images below the target is closer and there's a pretty significant improvement in the little details with the higher bitrate. These are crops of about 10% of the full image with a 3.6 mm lens.

 

[pur1337]

I mostly agree with you on this, with the exception from my experimenting the resolution isn't totally pointless. When I run a 2MP and 4MP camera at the same bitrate the resolution on the 4MP camera is somewhat better. At a higher bitrate it improves more. If you need better resolution in only part of the image, ROI can make a big difference. It shows what the camera would be capable of at a higher bitrate than we're allowed to set it to. My 5442s' max bitrate is 20,480 kbps. I don't use the very latest firmware, so don't know if that's a factor.

Just for the heck of it I saved some snaps at 8192 and 20480. With the target greater that 50 feet from the camera I don't see much if any improvement at the higher bitrate. Perhaps the pixel resolution is maxed out. In the images below the target is closer and there's a pretty significant improvement in the little details with the higher bitrate. These are crops of about 10% of the full image with a 3.6 mm lens.

Thanks for chiming in on this. Perhaps I have just not dug through enough threads, but this is good to know. 20,480 kbps would be good enough at (2688×1520). I can live with lower FPS.

Also, great to see such a good community with such fast responses. I think I'll stick around!