Magic Lantern Forum

Using Magic Lantern => General Help Q&A => Topic started by: Walter Schulz on January 18, 2015, 04:24:34 PM

Title: 4GB file size limitation - Revisited (ExFAT enabled cameras)
Post by: Walter Schulz on January 18, 2015, 04:24:34 PM
Hello!

Old news for devs, maybe. Maybe something there to help. Don't know.


Prologue:
In some documents like FAQ you will find something about maximum recording time
Quote
How do I record for more than 12 minutes?
[...]
Technically, there's no 12 minute limit. There's a 30 minute limit and a 4 GB limit, whichever comes first. With default bitrate settings, the 4 GB limit is reached after around 12 minutes (more or less).

For 650D this is not true and I suppose (!) it might be the same for all ExFAT enabled cameras. The only limitation with 650D is 29:59 (aka: 30 minutes).


Testing:
Test 1:
ExFAT formatted card (32 GB) with non-bootable card. Cluster size was 256 kByte = 262.144 Bytes.
Run a H.264 recording (1920x1080@30fps) and waited for a stop well before 20 minutes. Nope, run until 29:59 was reached and stopped there.
Recorded files were 2 with about 4 GByte + a smaller one.
File size (= cluster used) for the big ones: 4,278,190,080 Bytes

Test 2:
Formatted in cam which resulted in FAT32 with 256 kByte cluster size and recorded again with settings above.
Stopped at 29:59, too. Fun thing is: File sizes (= cluster used) reached were 4,275,830,784 and 4,278,190,080.

What I found (hit me, I'm not a developer):
650D's firmware is able to splitt files on it's own without loosing a frame (as far as I could tell) and 4 GByte limit does not apply to 650D (and maybe to all other ExFAT enabled cams on ML's scope).
Wondering why file sizes (in clusters used) are not identical.

What I really don't know:
If it is of any help for devs. I don't know if MLV/RAW recording is using it's own routines for splitting files or if they already use Canon's native procedure (if even possible).
And why the hell is Canon splitting files on ExFAT formatted cards at all?
(Note to self: Compatibility, I bet!)

Corrections welcome.




Title: Re: 4GB file size limitation - Revisited (ExFAT enabled cameras)
Post by: markanini on October 10, 2016, 10:36:24 AM
Cool find. On my 600D with an exFAT card I haven't been able to get around the 4GB limit. I used a bootable 16GB SDHC card with 32k clusters. Maybe it's down to Digic IV on 600D vs Digic V on 650D? More testing by the community on different cameras would probably help.
Title: Re: 4GB file size limitation - Revisited (ExFAT enabled cameras)
Post by: Walter Schulz on October 10, 2016, 10:51:06 AM
As manual says on page 151:
QuoteDue to limitations of the file system, movie shooting will stop automatically if the file size of a single movie clip reaches 4GB.

Therefore my assumption (about ExFAT enabled cams) was wrong.
Title: Re: 4GB file size limitation - Revisited (ExFAT enabled cameras)
Post by: kontrakatze on October 10, 2016, 08:38:48 PM
Which all leads to an old problem, where exFat formatted cards would change to FAT again if formatted within the camera. In addition mlv_play is still limited to 10 chunks, if I'm not mistaken, and crashes if there were more than 10 recorded...

By the way, there was some code by a1ex (experimental), which would enable the camera to format exFat, or at least leave the format as it is. But I have no idea what happened to this. I never found it again.

Regards,
kontrakatze
Title: Re: 4GB file size limitation - Revisited (ExFAT enabled cameras)
Post by: Walter Schulz on October 10, 2016, 09:23:36 PM
This is the thread you are looking for: http://www.magiclantern.fm/forum/index.php?topic=13983.0
And - as said in thread - it depends on cam type how ExFAT formatted cards will be treated. 650D will format 64 GB cards with ExFAT on its own.

Have you opened an issue about MLV_PLAY on bitbucket?
Title: Re: 4GB file size limitation - Revisited (ExFAT enabled cameras)
Post by: kontrakatze on October 11, 2016, 08:52:34 AM


About exFat, it's true. Cameras handle it differently, but wasn't there a code snipplet offering to choose the format at least for the 5dm3?
Regarding mlv_play, no, it was already open or known at this time.

Regards,
kontrakatze
Title: Re: 4GB file size limitation - Revisited (ExFAT enabled cameras)
Post by: Walter Schulz on October 11, 2016, 09:27:18 AM
Quote from: kontrakatze on October 11, 2016, 08:52:34 AMbut wasn't there a code snipplet offering to choose the format at least for the 5dm3?

Would you mind reading linked thread?
Title: Re: 4GB file size limitation - Revisited (ExFAT enabled cameras)
Post by: kontrakatze on October 11, 2016, 09:53:15 AM
Oh my, I did. And yes, there was. And yes, again he said it is experimental. And yes, was written some time ago. And yes, it is not in the regular repository.
It was meant as a kind of polite asking for the status of this code. May I ask you, if reading somehow between the lines is one of your specialities?

over and out