Bikecams and AVI file sizes - what is going on?

[Andy_Pagin]

Specifically I've just started using a Vivitar DVR480 cam on my commute.

The journey time's anything from fifty minutes to an hour and a half, and the resulting .avi video is usually about 2 to 3 gig.

However on the first day of the tube strike I had a really fast run into London until I hit Shoreditch when I ended up at a more or less complete standstill for about twenty minutes followed by a slow crawl to the car park.

The total journey times was about an hour and a half, but the .avi file hit the 4.3 gig limit and the camera stopped after fifty minutes.

So why the vast difference in file size when the only difference in the journey was an exceptional amount of stationary time?
____________________
They're coming to take me away, ho-ho, hee-hee, ha-haaa, hey-hey,
the men in white coats are coming to take me away.
Yamaha Vity -> YBR125 -> FZS600 Fazer -> FZ1-S Fazer

[CaNsA]

VGA: The video clip size is higher and the quality is better when the resolution is VGA than that is QVGA.
QVGA: The length of recording is longer when the resolution is QVGA than when the resolution is VGA

theres your answer that i found after 3secs of looking in the manual.....

RTFM motherfucker

[Rogerborg]

[doggone]

I suppose it's possible that properly resolving almost stationary surroundings uses a lot more space than the 'blur' of things whizzing past.
You should try a simple test with it on the table or running round the room for 5 minutes.

[Andy_Pagin]

[Rogerborg]

Were you stuck next to a group of dancing clowns?
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Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

[Andy_Pagin]

No clownsPCSOs, just the usual central London rush hour street scene.
____________________
They're coming to take me away, ho-ho, hee-hee, ha-haaa, hey-hey,
the men in white coats are coming to take me away.
Yamaha Vity -> YBR125 -> FZS600 Fazer -> FZ1-S Fazer

[Pete.]

Could be something as basic as lighting levels couldn't it? If it's darker there's less detail. Won't that affect compression levels?
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[WD Forte]

Dunno
maybe its just not that good?
maybe the firmware is a bit iffy and doesnt handle the encoding and allocating memory very well?
the fact you can fit a 16Gb card but it will only record up to 4.3 gigs
in one go isnt very impressive.
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bikers smell of wee

[Andy_Pagin]

The 4.3 gig limit is a limit of the Fat32 file system.
____________________
They're coming to take me away, ho-ho, hee-hee, ha-haaa, hey-hey,
the men in white coats are coming to take me away.
Yamaha Vity -> YBR125 -> FZS600 Fazer -> FZ1-S Fazer

[WD Forte]

Ride faster?
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bikers smell of wee

[barrkel]

tl;dr: it's because your camera has a cheap video encode chip that makes it more expensive to record still pictures than moving pictures.

Motion JPEG is a concatenation of JPEG files. It has no inter-frame compression; it is no cheaper to compress a fixed, unchanging picture than a succession of completely different frames. Quite the opposite, in fact, when it comes to motion.

JPEG compression is normally quality oriented rather than bitrate oriented. That is, you choose how much precision you're going to cut off, but if the image has high information content, you'll still have a lot of data. Encoders do not generally have file size targets, such that they change the quality to fit the image in a particular size.

Sharp, focused images of static scenes with lots of detail have high information content. Road has texture, bricks, windows, people, etc.

Blurry motion - especially when captured by a cheap cmos sensor - has low information content. Road turns into a smoother grey / black streak, bricks are blurrier smudges, etc.

To demonstrate this, I took a standard test image in PNG format - Lenna - and saved it with Photoshop, Quality 9, "Baseline Standard". It came out at 111KB:

https://i.imgur.com/Gg2bAUi.jpg
I reopened the PNG and applied a radial zoom - simulating motion blur - and saved with the same JPEG settings, coming out at 62KB:

https://i.imgur.com/oqeVTtM.jpg
Imgur has re-encoded the JPGs, but the space differential is still there (in fact, it is larger). The first, unblurred image is 81KB, the second, blurred image is 38KB. Blurry images - like successive frames recording motion - are as much as half the cost to store.
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Bikes: S1000R, SH350; Exes: Vity 125, PS125, YBR125, ER6f, VFR800, Brutale 920, CB600F, SH300x4
Best road ever ridden: www.youtube.com/watch?v=s2MhNxUEYtQ

[Andy_Pagin]

Thanks for the full technical explanation. I only paid twelve quid for the camcorder so I can't complain.
____________________
They're coming to take me away, ho-ho, hee-hee, ha-haaa, hey-hey,
the men in white coats are coming to take me away.
Yamaha Vity -> YBR125 -> FZS600 Fazer -> FZ1-S Fazer