16 replies to this topic

[jameswilson]

I have been putting a new dvr through its paces over the last few weeks. (ill do the jokes ) I have always avoided anything higher then 2CIF due to interlace issues and general poor performance at D1 on any PAL camera (obviously decent IP cams are ok at this res) But seeing how this thing i have performs at D1 i think im changing my mind. I know there is an increased storage demand etc but as ive previously said id rather have 2-5 fps of real quality then 12 fps of poor. As a compromise i have been using the video motion detector to increase framerate as req (suprisingly it even keeps the pre alarm at full framerate) Anyway Genuine question what do you lot tend to set your dvrs on and why? Neednt say machine type if you dont want to.

Ill start
DM Digi sprite 2's
4 ish fps per cam. Not dynamic fps but do use the interleave function and 2 CIF.

[Adi]

6 fps @ d1 record all the time, i used to do motion only.

think i changed due to recommendations on here.

[mma]

I also set it up on around 6 fps on d1. I never use motion only. Have missed incidents in the past. I think its better to have a higher quality than higher frame rate. Would recommend using a dvr were you can set up each cameras frame rate individually so higher rates for areas such as entrances to car parks with fast moving objects. No use installing high res cameras if you don't record at a high quality.

[alterEGO]

mma, on 18 October 2010 - 10:05 PM, said:

Would recommend using a dvr were you can set up each cameras frame rate individually so higher rates for areas such as entrances to car parks with fast moving objects. No use installing high res cameras if you don't record at a high quality.

Don't they all do this anyway these days?

Normally 5 fps ish, normally D1, 2cif on some of last years machines.

[jameswilson]

I always assumed 2cif was the best that could be achieved. Can some of you using D1 do me a favour and export some footage at D1 with movement in the scene?

[hpotter]

depends on dvr eg jpeg or h264, cams used, and view.

been meaning to link up a sprite2 & alienU to play together, see if have time over w/end.

[jnealon]

Sorry for bringing up an old post

Have any of your opinions changed in the last year. I usually use anything from 8-12fps @ D1.
At what frame rate do you reach saturation, I used to think 16fps was the cut-off point where anything beyond that wasn't noticeable


I have an audit for EN50132 next month ant want to be prepared for every question, one being why don't I record in realtime

[jameswilson]

i dont think you get much benefit of anything above 12 fps.
However if the view is wide then fps is less important.
I posted this a bit ago which does a good job of showing fps vs captured images at a set target speed.

Attached Files

•  FramesPerSec_Metric.pdf   893.46K   14 downloads

[fozzies]

According to a secured by design policeman i met in west london last month, they will be looking for a min of 12fps at D1 in the near future....
Cant complain at that, think of all the extra storage and the quality of the 16 ch dvr needed to acheive that

[fozzies]

Thinking back, he didnt state d1, just the 12 fps. unable to edit my post so had to repost

[jameswilson]

problem is d1 at a sh1te bitrate is worse then cif. also some dvr's dont tell the truth about their actual framerate, and lets be honest how would an installer test. You select 12 fps you assume thats what its doing.
It can be tested but not easily, id be curious to know how many installers do actually check the claims.

[fozzies]

Surely d1 is the best record level possible? cant say ive ever seen cif better , cif is something like 320* 200 pixels, whereas d1 is 720*480 ish. thats something like 4 times the quality( hope my maths hasnt let me down here). I guess there may be some compression that could destroy that quality, but uncompressed d1 has to be king. i guess it entirely depends on the dvr in question

[jameswilson]

id agree but a lot of dvr's have a limited max bi rate. They look great live but movement causes artefacts that on the cheap units are worse then recording at cif.
its not as simple as resolution. Its like comparing engine sizes. some have more power than others you cant compare on specs alone without being aware of the things the specs dont tell you.
h264 is a complicated recording system. Its not just about res and framerate. I have done some research on it and you can see that on a review i did here.
Your final comment is bang on though ie it depends on the dvr and all the factors that go into it. It may run constant bit rate, it may run variable bit rate. You need to know it upper limit on bitrate and wether its hard ware or software etc. a member here digital witness knows far more on this than i do.

[fozzies]

I guess the moral here is to ignore the £500 hbl specials and stick to dm etc.
Only time ive ever seen any bad d1 recordings is when i was once called in to comment on a "professional"instalation, but that dvr had chinese hyroglyphics on the front of it!

[jameswilson]

its not just dm, there are some units that dont have a main brand name that can out perform the dm. But most of them are shockingly bad imo. but look good on specs

[jnealon]

From what I'm hearing installers only record realtime because they can and the equipment will do it.
Has anyone ever been in a situation where they missed something due to low fps, usually it's down to quality of the images and not quantity

[mma]

jnealon, on 14 September 2011 - 06:07 AM, said:

From what I'm hearing installers only record realtime because they can and the equipment will do it.
Has anyone ever been in a situation where they missed something due to low fps, usually it's down to quality of the images and not quantity

I agree. Have had times were the images were useless because of a low resolution. Normally because the customer changed their mind on how long they want to record for. Only ever missed an incident due to fps in the days when you could get 50 fps across the board on a 16 channel dvr.