D7000 users: Reason for the 20 minute video limit?

1

1128media

New member
Hey all!

***Please don't TLDR this thread***. I've been wanting to ask this question since the recent developments on hacking the D7000 firmware appeared, and I thought this was one of the best communities to raise the question to (don't hate me :P).

D7000 users: Can we possibly establish the real reason behind the 20 minute video limit in our DSLRs? I know the issue has been brought up before around the web, but I don't find most of the given answers satisfactory. I'd like to hear your opinions.

So, I'll start us off with what has been suggested before, and my thoughts on each:

1. Overheating
This reason has been quotes for many cameras; sometimes it is legit, sometimes not. I tend to think not. Some have pointed out that overheating tends to happen more to compact cameras, due to the lack of space for heat dissipation. DSLRs would tend to benefit from their larger mirror box and lower sensor pixel density, meaning less heat production and better heat dissipation.
I do know that I personally have recorded 60-80 minute sessions of video straight (20 minutes clips of course, with about 1.5 seconds delay between each) several times without problems and without any noticeable damage to the camera. At the end an 80 minute session (limited by battery going flat) I would estimate the camera was perhaps 15C warmer than ambient temperature to the touch, probably not much more than that. That's still cooler that some of the compact HD camcorders I've used before. (Someone please warn me if this is actually damaging my camera!)

2. Sensor/Image processor incapable
Actually I think this one was more in regards to frame-rates, but it's one of the possibilities on the list. Again, doesn't sound likely, partly because of the ability to take several 20 minutes clips in succession with a very minimal delay in between, and partly because the EXPEED 2 processor seems pretty capable.

3. FAT32 4GB file limit
This one is plausible. The FAT32 file system is by nature limited to a maximum size of 4GB for any one file. Throwing a 4GB SDHC card in my D7000 and setting the movie mode to 1080/24 @ 20Mb/s (highest quality) show me that the card can hold 22 minutes, to the 20 minute limit would be a good place to set the limit. What this theory doesn’t explain is why the maximum time doesn’t increase with the lower resolution/bitrate movie modes. One would think that Nikon would set the maximum time to be the closest duration yielding a 4GB file at the given bitrate. Opinions on this one particularly would be appreciated.

4. EU camcorder tax
This one again sounds plausible, maybe even likely, but we lack evidence. It has been stated in many places around the web that the EU impose a greater tax on camcorders than on still cameras. In several places the definition of a camcorder is said to be any camera that can record more than 30 minutes of continuous video at either a resolution higher than 800x600 pixels or a frame rate higher than 23fps [citation needed]. However, is this issue great enough to be the sole reason Nikon imposes a lower time limit? Probably, but the topic would benefit from some debate. Opinions on this one would be greatly appreciated.


So, what does everyone think? Maybe you have a different suggestion than the ones above. Go ahead and put it up here!


Thanks,
Matt


**I’ll leave my reasoning for this discussion for the second post. See below if you need to know.
 
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The reason for this discussion is that the D7000 (and D5100) firmware has been more or less successfully decrypted and the checksum algorithms identified, meaning we are now at the stage where a few people might begin decompiling and modifying the firmware to add or improve features (I myself might possibly join this group). I would think that one of the easier hacks (and I say that lightly, as nothing is easy when dealing with assembly code) would be to up the recording time limit or possibly make it unlimited. This is not one of the main hacks being requested, as most are interested in higher bitrates and live histograms and such. Which actually makes perfect sense for filmmaking, and unlimited recording does not. However, I personally am interested in longer recording because I have been using my D7000 for a fair amount of event video. I know that sounds stupid – why would you buy a D7000 for event video – but at the time I was a photographer first, videographer second. Since purchasing the camera I have actually been doing more video work than still photography. So, for any others who would find themselves in the same situation as I am, I think this particular firmware hack would be appreciated.
 
My D5100 does not overheat when I push the record button immediately after each 20 minute segment.
I have done this as many as 4 times in a row.
I would like continuous recording for one hour or more please.
 
Ok, thanks guys, yes I get the fact that you want to see more features in the firmware. Everyone does. There's no guarantee that I personally will be able to contribute anything to the firmware hacks directly - I'm already having some trouble just setting up the tools for IDA Pro. Even after I get that working, I think I'll likely be looking for code segments to point out to Vitaliy and others who actually know how to code the changes properly.


But in the mean time, can we please get a little more research/experience/opinion discussion happening here?
 
The FAT32 4GB file limit is the overriding issue with video recording limits. On the Panasonic GH1/GH2, the camera automatically spans long AVCHD videos across multiple 4GB files. This crude workaround is made usable by index files stored in the SD card's PRIVATE folder structure. This is how video editors and players are able to seamlessly play back a spanned video.

The D7000 doesn't store videos in AVCHD format, it records H.264 MOV files stored in a DCIM folder. Even if there was an easy way to hack the camera to span videos across MOV files, there would be no standardized way to indicate to a video editor which files should be joined together. In reality, none of this would be easy to implement or test.

Live View histogram while recording is another wistful feature that is not likely to be feasible in a patch. The D7000 and D5100 display histograms only in playback mode, in a separate pane on the LCD. There is no evidence that the camera has a hidden ability to superimpose a live histogram window over the video frame while recording, and crafting such a feature would be an ambitious project requiring extensive knowledge of lower level firmware interfaces.
 
Ah, thanks lpowell, that's the sort of info I was after! I wondered how other cameras get past the 4GB limit, I just hadn't gotten around to looking that up. So if, as you have stated elsewhere, the D7000 uses a hardware H.264 encoder, it would also be impossible to implement a different codec such as AVCHD or MJPEG in the Panasonics. Ah well, no one said the Nikons would be anywhere near as versatile as the Panasonics :cry:

So the conclusion might be that the recording limit might be tweaked to be the maximum length inside a 4GB file in the given resolution/bitrate. This would be similar to Canon's implementation, though Canon's limit is also hard-capped at 29min 59sec, probably because the EU tax covers cameras recording 30 mins or longer.
 
lpowell said:
The D7000 doesn't store videos in AVCHD format, it records H.264 MOV files stored in a DCIM folder. Even if there was an easy way to hack the camera to span videos across MOV files, there would be no standardized way to indicate to a video editor which files should be joined together. In reality, none of this would be easy to implement or test.
Click to expand...

It's pretty trivial to round up any number of sequential clips and insert them on a timeline. Takes about 5 minutes for an hour.
 
I was testing my Swivi monitor's battery life, which required to keep my D7000's LV on continously. LV stayed on for 1:45 with no issues (the Swivi started its 15 min battery countdown at that point).
 
1128media said:
Ah, thanks lpowell, that's the sort of info I was after! I wondered how other cameras get past the 4GB limit, I just hadn't gotten around to looking...though Canon's limit is also hard-capped at 29min 59sec, probably because the EU tax covers cameras recording 30 mins or longer.
Click to expand...

Canon's limit is 12 minutes. Perhaps you meant Sony? Their cameras are capped at 29.

Cheers,

Bill
 
Let's put this into perspective.

20 minutes = 1800 feet of 35mm film. A 400' film mag would get you roughly 4.5 minutes.

You get 20 minutes of recording time with the D7000. You don't have to change mags. You just press a little button.

Alfred Hitchcock's "Rope" used 10 minute mags quite efficiently, and beautifully. I think you'll be ok with 20 minutes.
 
Aaron Marshall said:
Let's put this into perspective.

20 minutes = 1800 feet of 35mm film. A 400' film mag would get you roughly 4.5 minutes.

You get 20 minutes of recording time with the D7000. You don't have to change mags. You just press a little button.

Alfred Hitchcock's "Rope" used 10 minute mags quite efficiently, and beautifully. I think you'll be ok with 20 minutes.
Click to expand...

Aaron - for narrative film, 20 minutes is OK. For event recording when you don't want/have a camcorder (speeches, plays, sermons, etc.) it is not.

Cheers,

Bill
 
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