Beginners Question: Do I Need to Watch Out for Gigabyte Limit?

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Denniscasey

Well-known member
On another forum person noticed skips when adding long clips from HMC41E to NLE timeline. Thread revolved around 2 gb limit per clip and need to “join” or “stich” clips before importing to NLE--although thread starter also wondered if slow SD cards were the real culprit. If real this gigabyte limit is yet another thing new to me in world of file based video.

My bit of research on this forum turned up old posts (some back in February, 2009) referencing 4 gb limit on HMC150 related to FAT32 and even a "program" by a forum member (“pailes”) to re-join split files. Then other posts on thread got into "I" frame in long GoP, Entropy Encoding, Content Adaptive Binary Arithmetic Coding. Cool terms but I have no idea, so asking following questions:

(1) Is gb limit still an issue when adding clips to NLE timeline? If so, at what gb does “limit” occur (have seen references to both 2 gb and 4 gb limits per clip) and does it only apply to single continous recording clip that exceeds gb limit. Right now I am recording only short clips (less than 30 seconds each in most cases) so do I even need to think about gb limit?

(2) If I do get into split clip issue, did “pailes” re-joining program solve the problem? Sounded like a good solution. Also in other forum people were asking if Panasonic AVCCAM Viewer joined clips to solve problem?
 
I'll tell you as much as I know here...

The 4GB limit is a FAT32 file limit. While Panasonic could have made the file size larger using a Windows only or MAC only format, FAT32 was the one file type common to both.

If you are recording a bunch of short clips, none of them reaches the 4GB limit. However, a long recording of over 20 - 22 minutes is about all the can fit on a 4GB file. Thus, the camera must close the existing file and open a new file. In reality, NOTHING is lost between the files, but some software will drop a frame or 2 between the files. This results is a short glitch or missing section between the clips. The missing part is on the source files, but the software you are using removes the opening and/or closing frames out.

One trick is hide the glitch is to pause recording at a dead spot and QUICKLY start it again. (This assumes that you have the 3 second per-record turned on.) This creates a break during a time where a glitch can be cut out and not be noticed. With pre-record on, everything is still recorded to the next clip as long as you start the camera BEFORE the 3 second pre-record time expires.


Bob Diaz
 
Thank you, Bob, very helpful practical answer including a good real world work around if ever needed (very short pause with pre-record on). AVCHD and file based HD video is brand new to me so still learning what I really need to watch out for when I am recording video in terms of impact it will have later in production flow--i.e. impact on Blu-Ray recording, impact in NLE editor, etc. Of course the photographic elements (lighting, composition, etc) are still the most critical.

Dennis
 
Dennis, Sony Vegas creates a minimum fade in the audio file, causing a minimum volume fade between clips, what you have to do if you use Sony Vegas Pro, is that you manually eliminate the fade. The results a seamless recording of as many hours as your card can take
 
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Felipe Henao said:
Dennis, Sony Vegas creates a minimum fade in the audio file, causing a minimum volume fade between clips, what you have to do if you use Sony Vegas Pro, is that you manually eliminate the fade. The results a seamless recording of as many hours as your card can take
Click to expand...

Felipe, thanks again. As I am learning (at this stage still reading a lot), another factor that has some impact on recording format and technique can be the "preferences" and also "issues" one's NLE has processing the data. For instance, in many other threads I have read 720p seems to require less processing within NLE vs 1080i. Of course I understand there are many higher priority issues impacting recording format choice, but IF final output looks as good on high def TV in 720p as in 1080i then "easier" processing in NLE would be favor choosing 720p as recording format. I should note, my planned output is to Blu-Ray burning and not broadcast tv. Dennis
 
Denniscasey said:
Felipe, thanks again. As I am learning (at this stage still reading a lot), another factor that has some impact on recording format and technique can be the "preferences" and also "issues" one's NLE has processing the data. For instance, in many other threads I have read 720p seems to require less processing within NLE vs 1080i. Of course I understand there are many higher priority issues impacting recording format choice, but IF final output looks as good on high def TV in 720p as in 1080i then "easier" processing in NLE would be favor choosing 720p as recording format. I should note, my planned output is to Blu-Ray burning and not broadcast tv. Dennis
Click to expand...

Dennis 720 from the HMC40 in Sony Vegas and probably in others, requires more processing power, that probably happens because despite that you have various frame rates in 720, all the frame rates have a frame frequency of 60p. However I've noticed motion is smoother in 720
 
By the way Dennis the short fade was created in Vegas 9, The new version Vegas 10 don't create the fade
SO just put one clip after the other and without adjustments will be a seamless recording
 
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This glitching problem became evident to me after recording a 3+ hour concert with my HMC40.. I use Premiere Pro CS5 and when I laid the files on the timeline, there was a short glitch/dropout between each one. I found out about a program called txMuxer (actually I use tsMuxerGUI), which will join all your files together seemlessly.
 
BobDiaz said:
One trick is hide the glitch is to pause recording at a dead spot and QUICKLY start it again. (This assumes that you have the 3 second per-record turned on.) This creates a break during a time where a glitch can be cut out and not be noticed. With pre-record on, everything is still recorded to the next clip as long as you start the camera BEFORE the 3 second pre-record time expires.


Bob Diaz
Click to expand...

Sorry, Bob - you usually give great advice but this is way off, and not useful for many long-form shooting situations....

The AVCHD file hierarchy carries information needed to properly stitch the files together. One should NOT add individual subclips to the NLE timeline and abut them... most NLEs today wil properly stitch the clips if you point them at the top-level ("NO NAME" or "PRIVATE") folder rather than trying to work with individual MTS files. E.g., if you have a card with 2 1-hour clips, which are spanned across 2 or 3 MTS files each, when you Log and Transfer in FCP it shows 2 1-hour clips, and ingests them as seamless 1-hour clips.

There is no need to worry, or especially to start and stop recording!!!!! Just make sure you understand the proper way to ingest AVCHD footage into your NLE. I shoot classical music events daily, with almost everything involving clips that are over an hour long. If there were glitches every 4GB, or the need to run them through an extra stage of "stitching" in some other software, these cameras would be useless to me... luckily, the NLEs do exactly what they should!
 
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BobDiaz said:
With pre-record on, everything is still recorded to the next clip as long as you start the camera BEFORE the 3 second pre-record time expires.
Click to expand...

Also, have you tested this? I did, a long time ago, with a different camera... and found that the prerecord buffer seemed to be flushed somewhere between stopping recording and starting again... such that there was no way to use this trick without at least a few frames being lost. This may not be the case with the HMC40, but it would be good to have it tested!
 
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