GH2 Running out of bandwidth/blocky image

M

MarcusWolschon

Active member
On 2 occations I had the video recording get completely blocky:
* stroboscope in disco
* lots of leafs moving in the wind.
The bitrate is already upped to the maximum my SD cards can handle.

Any ideas how to counter this effect except to get faster SD cards and up the bitrate even more?
(The recordings already got too big, so that transfer time and storage on site where at a practical limit.)
Does anyone know if the firmware has a logic to give the encoder a hint to prefer the object that is
being focused on (spot/face/center vs. matrix) in it's bitrate allocation? (Some cameras seem to have such a thing.)
 
Is your camera hacked? If not, I would highly recommend doing this if you want to get the best from your camera.
 
There is only the hack from Vitaly, is there?
His current ptools and the 1.1 firmware.
I'm pretty sure all the bitrate settings in that tools are named "<mode> bitrate" and there are no translations into any other languages.
The footage is not public and wouldn't help anyway.
It should be obvious how an image that gets blocky looks and that the reason in the kind of scene I named is. That simply every pixel in the images changes all the time.
What I'm asking for is not to find the cause but for people who experienced the same issues or have insight into how the bitrate allocation is handled to come forward.
I could imaging a shorter GOP to help somewhat but have no experience with the side effects this has and how I could set things up to choose between this and a conventional mode on site.
 
MarcusWolschon said:
There is only the hack from Vitaly, is there?
Click to expand...

There is one hack, but many "patches" which is what tweaks the encoder.

The footage is not public and wouldn't help anyway.
Click to expand...

Sometimes the words that people use to describe problems are not as accurate as they could be. This is why showing the problem helps more often than not.

What I'm asking for is not to find the cause but for people who experienced the same issues or have insight into how the bitrate allocation is handled to come forward.
Click to expand...

I have never had this problem, so apparently there is a solution.
 
Did you actually film a stroboscope lighted scene or a wall of moving leafs for more then, say 20 seconds?
It's certainly not a common situation and these are the first times this has ruined some shots for me.
It works for a few seconds, then degrades visibly. Just as you would expect if you run out of bitrate for your stream and favor motion over details.
Thinking about it, I think I remember a setting where I could give more priority to detail vs. motion in ptools. If I can reproduce the problematic scene, I could play with that.
(No idea if I can reproduce it. I don't have a stroboscope, dense tree in reach for a ventilator or a waterfall at hand. Maybe use a computer monitor.)

Actually these would be presets for ptool and not patches. A patch would be a diff to modify actual firmware code. The nomenclature often used surrounding ptools sounds just wrong to any software developer.
I'll have to check but I think the GH1s used as secondary cameras experienced the same. (They are usually static with a wide lens while I run around with the GH2. So they don't get to see such frame-filling motion over any prolonged time very often.)

I started with the eoshd unified set, lowered the bitrates in fsh and fh mode to something my SD cards can handle.
I ended up at about twice the default rates. Don't want to buy high end cards before the GH3 with it's two unknown SD slots is released.
The settings in ptool are pretty straightforward and well explained. No changes made to any experimental settings.

I used 25fps in the high bitrate mode. I wanted 25p but for some reason the resulting footage had interlacing artifacts if played with VLC
without a deinterlacing-filter applied.
Doing multicam in europe using anyother framerate (e.g. 24p) makes no sense.
 
Without knowing exactly what your "settings" are, using pTools, none of us can apply them to our cameras to try and help you by seeing if we can recreate what you are seeing.

Without at least a picture example of the blocky footage (cropped section of the image) we can also only assume that what we are seeing is what you are seeing - or we might not even see it because for our standards we don't notice it.

Without knowing exactly what you are filming none of us can try and replicate the condition. Even a picture will help. My idea of falling leaves in a forest is different to say Gary Huffs' idea. Plus throw in the variables of time of day, direction of the sun, camera stabilizer rig (if any), camera movement (running around fliming vs panning via a fluid head), lens focal length, possible filters and filter brands, AND the exact SD card you are using, we cannot help you - we can only speculate.

And yes, I suppose from a software developer point of view the jargon might be incorrect regarding hacking and patches and settings and the like, but the jargon from the point of view of those that use the GH2 and hack it, the "Hack" is ptools that Vitality developed. The "Patches" is a combination of changes made to the firmware - whether it be the actual code or merely variables in the code is not important we call it patches. We just know that we load "patches", or we play with the "settings" (or bitrate/GOP values) ourselves, and we can save those changes as a "patch".

Hope we can help.
 
Marcus,

Most likely the only option you have is to purchase high performance SDXC cards so that you can shoot at the higher bit-rates. Some patches are better than others, but there is no magic-bullet when it comes to bitrate.

I went out and bought two of the pricey Sandisk SDXC 95MB/sec specifically so I could shoot at the higher bitrates and still have my footage span with longer recordings.

I also switched to USB 3 card-readers ( the IoGear reader is only $15 ) which will almost double the read speed ( 35+ MB/sec ) when using USB 2 computer ports, and almost quadruple the read speed ( 70+ MB/sec ) when using USB 3 computer ports.

As for file size, you just have to get used to it. It's going to get a lot worse when the world switches to 4K video...
 
TheDingo said:
As for file size, you just have to get used to it. It's going to get a lot worse when the world switches to 4K video...
Click to expand...

That's what amazes me about people who primarily experience the world of AVCHD at 24 or 50Mbps clamoring for 4k...they are in for a shock!
 
MarcusWolschon said:
I started with the eoshd unified set, lowered the bitrates in fsh and fh mode to something my SD cards can handle.
Click to expand...

Yes, that could well account for the problems you've encountered. But unless you're recording at bitrates over 140Mbps, I doubt that SD cards faster than the standard 30MB/sec Class 10 cards will make a difference. (In my experience, 95MB/sec cards are primarily useful for insuring that 4GB file-spanning works reliably.) I'd suggest trying out some of the more well-tested, downloadable patches that have been developed for the GH2. There's one linked in my signature below.
 
There is no standard 30MB/s. At least not for minimum write rates.
Class 10 defines a minimum sustained, sequential write rate of 80 Mbit/s (10 MB/s) on an unfragmented card (classes <10 defined their rates for fragmented cards) and I have yet to see any cheap consumer "class 10" card that actually delivers that under all circumstances for hours on end until the card is full.
It makes no sense to take maximum or average write rates or even the much higher read rates they advertise with into consideration.

What do you think starting over with another preset would change?
(Except that I know for sure that my cards don't do 100Mbps reliably until the 32GB cards are full. )
What setting that isn't visible to me would any of them modify in what way?
Would it even make sense to use a GOP-length, bitrate and detail-vs-motion tuple that was gained by experimenting in typical situations in such an untypical one?
I don't remember a way to have different GOP-length and detail-vs-motion for the GH2 high-bitrate mode then for normal video mode. Is there?

Again:
Recording is fine most of the time but for situations that are extreme to the encoder I am looking for ways to affect the bitrate allocation. Not ways to increase the bitrate.
When the GH3 comes out and I know what cards it supports (just SD-XC or already UHS-1, ...) I'll get me some of the expensive cards that allow me to select 100Mbps and more for the fsh mode (and keep the fh mode at defaults because it's good enough for most things).
I don't think I'm the first one to run any camera in a disco with overused stroboscope light. What methods to other people use to deal with this?

What options I found so far are:
* experiment with using AF instead of MF and the focus modes spot and center to determine if more priority in bitrate allocation is given to the areas focused on or not. Since nobody here seems to know.
* increase the bitrate further and hope the camera doesn't lock up with "card too slow" or "write error" during the most important shots.
* try to reproduce such a situation and play with the details vs. motion bias. This has the best chances of success.
* play with the exposure times to average some of the flickering. Could of cause be a problem if the subject moves too fast.
* In the woodland situations mentioned, try to change the framing to have less of the leaves in the frame. Either zoom in on the subject if possible or zoom out/reposition to have the leaves cover less of the frame.
 
Here's an example of what is widely considered a "standard" 30MB/sec Class 10 SD card:

http://www.amazon.com/SanDisk-Extreme-30MB-Flash-Memory/dp/B002HFER6O

There are also newer versions rated at 45MB/sec and 95MB/sec. On the GH2 at peak bitrates no greater than 140Mbps, I haven't found the faster-rated cards to perform any better or worse than the older 30MB/sec cards (except for the file-spanning ability of the 95MB/sec cards). So within those broad limits, any of these cards should work reliably on well-tested patches.
 
MarcusWolschon said:
When the GH3 comes out and I know what cards it supports (just SD-XC or already UHS-1, ...) I'll get me some of the expensive cards that allow me to select 100Mbps and more for the fsh mode
Click to expand...

...Why wait for the GH3 to be released in the Fall, when your GH2 works perfectly with the current Sandisk SDXC 64GB 95MB/sec cards, and will record for 84 minutes at 100 Mbps. This is what I've been using since March, and these high performance memory cards have worked pretty much flawlessly for me when shooting at 100 Mbps.

MarcusWolschon said:
What methods to other people use to deal with this?
Click to expand...

Simple. It's a memory card issue, so buy the high performance memory card that has been proven to work with the GH2 ( SanDisk 64GB SDXC Memory Card Extreme Pro Class 10 UHS-I : $165 at B&H Photo ), and then pick the patch that best suits your needs.
 
Because I don't want to buy cards that I can't use with the GH3 later and I don't want to spend money on UHS-1 cards that may later turn out to be a waste of money.
150eur per memory card with 3 cameras and at least 2 cards per camera is damn expensive.
 
MarcusWolschon said:
Because I don't want to buy cards that I can't use with the GH3 later and I don't want to spend money on UHS-1 cards that may later turn out to be a waste of money.
Click to expand...

Ok, you've lost me here. The GH3 is definitely going to be compatible with UHS-I cards, and the UHS-I standard is not going away any time soon ( it's a future proof standard, which is planned to get much faster as technology improves ), I only hear that you don't want to spend the money on expensive memory cards, which I totally get, but I don't think there is any other reliable option.

The best performing low cost card I've seen are the new Patriot EP SDXC cards, which write at about half the speed of the Sandisk 95MB/sec cards, which will record at 100 Mbps but you will have to put up with a few small hiccups when using these cards. These cards will sometimes "stall" when you first hit record, so you might have to hit record a couple of times to get the card to start working properly. The more expensive Sandisk cards don't have this problem at 100 Mbps.
 
I don't see that mentioned in any of the rumors about the GH3.
Anyway, raising the bitrate is the last thing I want to try. It's the most expensive option for such a rare case and
all that material needs to be transfered and stored and archived and loaded into the NLE too.
I'd rather spend that 1000eur in replacing one body with a GH3 when the time comes or just live with having that issue.
 
MarcusWolschon said:
I don't see that mentioned in any of the rumors about the GH3.
Click to expand...

Yes, you should totally be basic purchasing decisions on rumors.

The cards will work. They are the future of the SD card design. Why do you think they would not work just because the "rumors" fail to mention it explicitly?
 
Gary Huff said:
The cards will work. They are the future of the SD card design. Why do you think they would not work just because the "rumors" fail to mention it explicitly?
Click to expand...

They will work but it may turn out that an SD-XC card for a fraction of the money will work just as well.
Why do you think I'm waiting for the actual release of the GH3 before buying any new cards?

To sum this up:
No one has any idea how to affect bitrate allocation, what indviidual settings affect the issue presented or practical advise on how to simply avoid such situations.
Everyone has only the one standard answer I explicitely asked not for and a simple "No clue, can't help you." would have told the same as these 2 pages of posting.
 
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