How to finalize an -av file?

ullanta

ullanta

Veteran
Greetings!

As you may know, FCP tends to capture a file with a name like "untitled-av", then do a touch of post-processing/wrapping to generate "untitled.mov". In general this post-processing is instantaneous so that when nothing goes wrong, you never see the "-av" files... although, if you limit the size of file segments, you'll get a bunch or "-av"s and one "mov".

Anyway, does anyone know of a way to take an isolated "-av" file and generate a playable quicktime movie?
 
Place them all into a timeline and export a quickTime movie. I'd also suggest not gulping in whole tapes at once which causes this to happen.

Noah
 
Thanks Noah - but I'm talking about an isolated -av file for which I don't have any associated .mov file - which FCP won't recognize. Actually, this is the result of a freeze after hitting escape on a Capture Now. It looks like the right asmount of data, just not properly wrapped into quicktime...
 
Typically if it won't open in FCP there's nothing in there to view. Anyways there's no repair utility or the like anyway. -AV files are temp files used internally by FCP, they should not be opened, moved or deleted.

Noah
 
NoahK said:
Typically if it won't open in FCP there's nothing in there to view.
Click to expand...

I'mm 99% sure this is not the case - that is, dureing the actual capture process, FCP always writes all data to an -av file, then performs a quick operation to turn it into a MOV. When using split file segments, the -av files of course have needed movie data, and won't individually open in FCP. So I think the av files are the raw DV stream, and it seems extremely likely a fairly simple process can turn them into a valid quicktime movie...

I'm just wondering if there's something out there already; if not, this weekend, I'll do some analysis of the file structure and see...
 
They are not RAW DV files. DV files have the extension .dv...the -av extension means that either your drive is formatted FAT32, and you have a 2 GB filesize limit (look at the size of each file) or you have a capture limit set in your CAPTURE SCRATCH preferences. This will cause the -av files. Now, the clip in FCP will work fine, because it links to all of these files, but try to open them on the finder level and you may run into issues. The first one will open fine, but the others may not.

SImple solutions:

1) reformat the drive as Mac OS Extended and re-capture the footage.
2) export the clips from FCP as self contained QT movies onto a separate drive that is formatted Mac OS extended.
 
That has happened to me as well when it freezes during a capture. It happened on a drive that was formatted Mac OS Extended. Not sure it has anything to do with the drive format. (not 100% sure though) I guess I just figured that the file didn't finish and I just delete and recapture. I wouldn't think there would be a way to "finish" wrapping it.
 
Dudes! This is NOT a file limit issue. I'm perfectly familiar with file-splitting. That's not what's going on.

FCP ALWAYS captures to an -av file at first (to see, do a capture now, and while it's going on look in the capture scratch directory you'll see an -av file growing as you capture). When you hit escaped, FCP does something to convert from the -av to a .mov. There's no .mov during capture; there's no -av after capture (when everything goes well and there're no file-splitting issues).

So, it seems that right when you hit escape, FCP converts the -av file to a quicktime .mov

Now if FCP crashes/freezes between when you hit escape and when the capture window disappears, you sometimes end up with the -av file but no .mov file. That is, the conversion from -av to .mov didn't happen.

I'k looking for a way to make it happen.
 
Here's how I understand the capture now process:

1) You hit the capture now button
2) FCP writes the DV stream to your capture scratch directory as, eg, "file-av"
2a) If there's a file size limit, it writes "file 2-av", "file 3-av" etc. as necessary
3) You hit escape
4) FCP converts file-av to file.mov.
4b) If necessary, the new file.mov references "file 2-av", "file 3-av", etc.

Now, when FCP is performing pulldown removal, step 4 takes more time than usual. In the old days (FCP 4), this process occasionally took 10 minutes or more, but that seems not to happen (much?) in FCP 5 and up.... that is, that may be what happened tgo me, but after waiting 15 minutes on a 1 minute capture, I had to guess it was not going to stop.


If something interrupts the process after step 3, you still have all the captured data in -av files.
 
Bottom line is there is something wrong with your install of FCP because you should never ever need to even touch any AV file and pulldown removal should be almost immediate. There's no way I've ever heard of to "reprocess" -av files. (But why take my word for it as I've been only using FCP since version 1.2 but anyways.) :Drogar-SunGlass(DBG

I'd go through the standard recovery procedure.

Trash Preferences and ZAP Pram- google for these if you've not done them before.
If the problem persists make sure you've got plenty of free hard drive space and that all drives are Mac OX Extended.
Not running Norton or Antivirus software.
Reinstall FCS and OS X- run all updates.
etc.

Again sorry you are having this issue but you should be fixing the disease not the symptom.

Noah
 
Ah, Noah - I've also used FCP daily for many years. There's nothing (big, anyway) wrong with my installation. This was one fluke crash among thousands of captures.

Anyway, so far it seems the only difference between an "-av" file and a working quicktime file is that bytes 7-10 of the quicktime files seem to have a file size indicator, while the same bytes in the -av file are zeroed. I don't know if it'll be as simple as calculating the proper size and plugging it in, but I'll let y'all know...
 
If you are not having capture limits set, and you are still ending up with a file that ends in -av...than something is wrong. You shouldn't have this. Not if things are working properly.

Heed Noah's advice.
 
Yes, clearly something was very wrong - the system crashed. That's clearly why I have an -av file. It crashed between step 3 and 4 of the process above.

Am I that unclear? I had a crash. I was left with an unexpected file, before the last stage of processing. Thisd is not a frequent occurence; it's a one time occurence. I am trying to recover this one take. I am halfway there at this point. But my system is generally quite functional in extensive daily use. I know what happened, why it happened, when it happened. I know exactly what functionality I need - something, clearly built into FCP as part of the capture process, that scans the -av file for information and builds a header.
 
I'll reiterate once again: There's nothing to recover and no secret tool available, you need to go back to the original tape and recapture this clip.

Noah
 
Well, there is no tape, it was captured live.

Anyway, as it looks, it is indeed easy to repair, I just have a few more details to figure out. For those who care:


An FCP captured file STARTS with a big MDAT atom with all the DV data. After escaping from capture now, FCP fills in the SIZE field of the MDAT, then postpends the moov and mvhd atoms. I'm not yet 100% sure what's flexible in the postpended atoms, but it seems that simple modifications of one or two size/format fields should be all that's necessary to "rescue" an -av file...

I've gotten it to the point where some of the clip will play before QT throws up an error... soon I'll have a set of simple instructions, and maybe cobble up an application if I'm bored.

more in a few hours...
 
I know where you are coming from ullanta. it isn't a bad install or any of that.

It has happened to me as well during capture and having the computer crash. Mine has happened from a tape so I just recaptured. But like Noah said you probably won't be able to save it unless you can go into the code or something like that.

But I didn't understand your problem right from the start. som I know what your problem is. Might have to reshoot, hopefully it is possible.
 
It's not a problem, no need to re-shoot - not a great take! But This is out of curiosity, and also for the occasional issue ofhaving a few segmented -av's without the main quicktime file that references them.

Anyway, it IS possible to salvage the file; I'm most of the way there and can get the footage playing a bit befoire problems start; I just need to do a little more reading on Quicktime format and some more splicing to make it work perfectly. Basically, hand-filling the MDAT's size field and splicing on the MVHD atom from another same-format quicktime file seems to get me 90% of the way there. Once I've done the testing, I'll write some simple code that'll automate the process...
 
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