Guide: Fitting Dual Camera Dvr System Focus Mk2 & Mk2.5

[salsheikh]

H.264 is a codec and bit for bit, is actually very good at delivering good results at reasonable file sizes, depending on bit depth, FPS and Resolution....

to be honest, if your recording 1080p at a combined bit depth of 20Mbps with H264 you wont get that amount of recording done.

I have a 64GB card, and two cameras recording at 1080p, 30FPS and 11Mbps on one stream and 9Mbps on the other, its full in about 4 hours.

4 hours?

this is 780p recording at 30/15fps (doesnt state Mbps) and i have a 32gb card - i dont know if a 64gb one will work in it....

[Dee_82]

1280 x 720 = 921,000 pixels
at 12bit per pixel = 11,052,000 bits per frame, or 1.4MB (MegaBytes per frame)
x 30fps 331,560,000 bits per second Or 41.4MBps (MegaBytes per second)
331.5Mbps = 41.4MBps

That is pure uncompressed RAW data, the codec will compress the image which is where the bitrate comes in
considering the best hardware cant achieve much more than around 20Mbps (and a bluray film is no much more than this 19-35Mbps) achieving 331Mbps is impossible so compression reduces this to a more reasonable level, the more compression the lower the bit rate and the lower the file size.


With a bit of maths, you can work this backwards to see file sizes, image size isn't as important when it comes to file size, bit rate is king. But the available detail is less on a lower resolution

If your getting nearly 9 hours of footage on a 32GB card that comes to about 7Mbps

7/8 (8 bits to byte) = 0.88MBps
0.88MBps x 60 seconds = 52.5MB per min
52.5MB x 60 Min = 3150MB per hour (3.1GB)
3.1GB x 9 hours = 28.3GB

although a 32GB card says its 32, its usable size a bit less than that.


If you knew the bit rate then you could work out the max storage size.

Uncompressed actual bit rate compression ratio Detail different
1920 x 1080 = 186 MBps 11Mbps 94%
1280 x 720 = 41.4MBps 7Mbps 83% 78% less detail

So based on that, you should find that whilst your image is compressed slightly less, 83% as apposed o my 94% you also need to keep in mind that a 720p image has 78% less detail or pixels,

in theory whilst 720 has less artefacts from compression, it will also contain less detail.

codec type has a huge amount to do with compression though so the numbers will only take you so far

The reason mine is only 4 hours is firstly because there is two streams, secondly about 30% of the storage space is reserved for motion / events, this doesn't get recorded over by normal driving so prevents you losing stuff by mistake and finally because its recording at approx 36% higher bit rate

actually I'm not sure why I detailed all that but there you have it, if you wanted to know, now you know lol

[Dee_82]

I ballsed up the compression ratio, ill correct it later, but whilst figure is wrong the idea is still the same, 720p videos will be compressed less but contain less detail

[salsheikh]

Er im looking for the ford owners forum.....this appears to be clever buggers forum!

I'm out

[Lenny]

I've edit this guide thismorning to transfer all images from the image host Photobucket over to the forum,

This means the images will now display forever without me having to pay a monthly fee to Photobucket.

The forum didn't host images back when I created the guides.

I plan to transfer all images in each of my guide's as I get the time across the coming weeks. 👍

[gloves]

Perhaps someone else has mentioned but you can make the hole for the USB port socket with a 28mm circular hole saw which cost a few pounds and connects to any drill.
Even if you already have a dremel i wouldn't bother with it because the hole saw makes a lovely perfect circle straight away.

[BigLen]

2 hours ago, gloves said:

Perhaps someone else has mentioned but you can make the hole for the USB port socket with a 28mm circular hole saw which cost a few pounds and connects to any drill.
Even if you already have a dremel i wouldn't bother with it because the hole saw makes a lovely perfect circle straight away.

Thanks for recommending the size; I didn't have a 28mm holesaw to hand at the time and had to improvise using the Dremel.

However the flange on the usb socket unit covers the imperfected circle.

[gloves]

1 minute ago, BigLen said:

Thanks for recommending the size; I didn't have a 28mm holesaw to hand at the time and had to improvise using the Dremel.

However the flange on the usb socket unit covers the imperfected circle.

yeah a 32mm hole works too (I tested it on a bit of scrap plastic) on amazon I noticed the products usually suggest a 3cm hole which isn't a holesaw size you can actually buy.

yeah it doesn't really matter at all granted 😂

[BigLen]

10 hours ago, gloves said:

yeah a 32mm hole works too (I tested it on a bit of scrap plastic) on amazon I noticed the products usually suggest a 3cm hole which isn't a holesaw size you can actually buy.

yeah it doesn't really matter at all granted 😂

I bought a set of cone head bits on amazon and the following week they appeared in my local Aldi for less but I had them at that stage, 

I wrap some PVC electrical tape around the maximum diameter I wish to make then drill, they have less risk of slipping compared to a holesaw and no dancing.

Link: https://www.amazon.co.uk/3PCS-Step-Speed-Steel-Drill/dp/B077JKSFRJ/ref=mp_s_a_1_2?adgrpid=70342480707&dchild=1&gclid=Cj0KCQjw5eX7BRDQARIsAMhYLP_gPgnFlrCYNe1rA0wuvwS2l1NpPpP7j6MVZEbWSXnetKNjTlDQnlQaAg0aEALw_wcB&hvadid=335514697896&hvdev=m&hvlocphy=20497&hvnetw=g&hvqmt=b&hvrand=3127262550938295125&hvtargid=kwd-1060365671&hydadcr=8644_1759947&keywords=drill+cones&qid=1601795810&sr=8-2&tag=hydrukspg-21 

[gloves]

2 hours ago, BigLen said:

I bought a set of cone head bits on Amazon and the following week they appeared in my local Aldi for less but I had them at that stage, 

I wrap some PVC electrical tape around the maximum diameter I wish to make then drill, they have less risk of slipping compared to a holesaw and no dancing.

Link: https://www.amazon.co.uk/3PCS-Step-Speed-Steel-Drill/dp/B077JKSFRJ/ref=mp_s_a_1_2?adgrpid=70342480707&dchild=1&gclid=Cj0KCQjw5eX7BRDQARIsAMhYLP_gPgnFlrCYNe1rA0wuvwS2l1NpPpP7j6MVZEbWSXnetKNjTlDQnlQaAg0aEALw_wcB&hvadid=335514697896&hvdev=m&hvlocphy=20497&hvnetw=g&hvqmt=b&hvrand=3127262550938295125&hvtargid=kwd-1060365671&hydadcr=8644_1759947&keywords=drill+cones&qid=1601795810&sr=8-2&tag=hydrukspg-21 

I saw these, they do look very good. Let me know how they are drilling through plastic if you end up using them.

[BigLen]

3 hours ago, gloves said:

I saw these, they do look very good. Let me know how they are drilling through plastic if you end up using them.

I used them on a friend's Toyota Yaris when fitting a usb 3.0 charger and a 28" LED light bar to the front bumper, the lighbar was cheaper than headlight restoration 😅

Very clean cut with them.

I put pvc tape on the plastic panel prior to drilling; there's less plastic dust with them more swirls of plastic than powder.