A ‘boy scout’ approach to recording Skype group video interviews

Pic of my ‘swiss army’ rig.

Lucky I had my trusty iRiver .mp3 recorder in-line with my headphones and a HD video camera pointed at my MacBook Pro when recording a Skype Group Video interview with Professors Corey Bradshaw and Bill Laurance for a TalkingPapers blog post. That’s because SnapzProX from Ambrosia software failed silently and recorded exactly nothing with zero warning or visual cues.

SnapzProX-SkypeRecordFail-Picture 1

Note the 13.364GB File Size estimate. For a 1338×501 px 25fps Millions vid the SnapzProX calculator estimates 226 GB space for the .rVid file in Snapz Pro X folder in ~/Library/Caches/

http://pinboard.in/u:fang/t:ambrosia/ – has a bunch more information, complaints from other disgruntled users and helpful links. It turns out I could have prevented this by using the work file calculator and then the OSX hack to move the work file location to an external HDD with more than 250GB  free!

You would think that Ambrosia could provide some UI to estimate workfile size based on chosen settings and to warn during recording. At the very least it could stop recording and salvage at least something without corrupting the work file.


I spent most of the weekend obsessing over exactly how snapz works with long recordings and limited disk space on startup disk.

  • 1hr Skype Video approx 1440×400 pixels, millions, 25fps is:
  • 1.5gb .mov file (30gb estimated by Snapz ‘movie info’ dialog)
  • 45gb .rVid work file (250gb estimated by Snapz size calculator on ambrosia website)
  • copy .rVid & .rMic \library\caches\Snapz Pro X before render works well (a good precaution for important / large recordings)
  • 2 x .mov disk space required as render writes .mo then copies to .mov at end
  • Moving scratch disk location process (alias in /library/caches) works but be very careful & make sure rename the alias in \system\caches to ‘Snapz Pro X’ (ie remove the work alias)

A dump of my notes during testing.


2:25 AT close to SkypeVideo Call
used 100MB rVid work file
which then took 
2x to render (five minutes for a 2min 25 sec recording)

Now leaving this to run for 1 hr to see what happens to work file when disk runs out.
I have just over 45GB free at 5min into the 1hr recording...
By that time the work file was 237MB in size.
Calculator for 1439x515 at 25fps Millions 1 hr:
Which means just over 11 min for my 45GB free.
But... 12min into my test the rVid file was only 525MB and rMic 203MB.  So *thats* clearly wrong...
Lets try playing my recorded skype call to see if it's the largely still screen / compression issues...
1.23GB to    2.3.... in 1min ... aha
> 1GB per min for video 
500mb in 15min for screen windows, typing & clock.
near 2:54pm I thought I saw a 10GB .rVid file with 35GB free on HD270. A few seconds later it was 9.22GB. WTF??
HMMM 10.1GB .rVid at 2:56pm
Bah at 3pm it was >13GB
at 3:15pm 27GB with 913MB rMic (17.3gb free) 
3:30pm 39GB with 1.17GB rMic (5gb free 
3:38om 43GB with 1.32GB rMic (1Gb free)
3:40 "yr startup disk is almost full (100mb free) - *didnt get this!!!
3:41 43.89GB 151.5mb free
3:42 same (has it stopped??? (cant see ambrosia - - - lines
Cmd+shift+3 no action...
Click SnapzProX in dock - nothing...
copy rVid and rMic files to 2TB

-1712 snapzproX cannot be launched..
then Movie capture was stopped because the disk is full. OK

Warning: You may not have enough disk space to save this movie (approximately 29199MB needed). Try changing compressor settings or delete some files before saving.

in SnapzProX Movie Info dialog.

So, we have a 1hr 12min 'recording'
577MB free
29199MB (30GB est .mov file)
4:30pm - begin SnapzProX render: 'save now'
warning: save anyway
4:45 < 1/4 status bar dubbing video track - 544mb free
5:05 < 1/3 " - 348mb free (280MB snapz.mov)
5:15 startup disk almost full warning (220mb avail)
5:15 < 1/2 thru video dub (376mb .mov 210 avail)
5:36 > 1/2 thru "unable to save movie because disk full"
Save Later
Clean up some space and start again. 2.76GB free
5:40pm - save now.
6:10pm - 171MB .mov, 2.1gb free Approx 1/3 status bar
6:40 - 500mb .mov 1.73gb free nearly 1/2 status bar
7:05 - 900mb .mov 1.35gb free approx 2/3 status bar
7:15 - 1gb .mov 1.2gb free approx 3/4 status bar
doing other things on mac...
7:30 - 1.2gb .mov 1gb free
7:45 - 1.4gb .mov 861mb free (nearly done dubbing video)
7:50 dubbing mic track - 1.4gb .mov 823mb free
7:51 saving movie to disk 1.41gb .mo copy to .mov
disk almost full
Unable to save movie because disk is full
drops both .mo and .mov - back to 2.21gb free

* so, roughly 2xX - 2hrs to render a 1hr .mov capture

Save Later
Snapz movie info says 29GB required (actually 2.8gb) to save
Snapz calc said 1439x515 24fps Millions = 239GB for 1hr (actually 44 + 1.4 = 45.4GB)

hd270 4gb free (eta 10:10pm)
10:22pm 1.41GB .mov file on desktop 1:10 duration (1439x415px 24fps millions h.264 2945kbits/sec
all good.
Library\Caches\Snapz Pro X\ folder empty - 52.5gb free.

- - -
quick test record create/del new .rVid rMic files
Copy saved .rVid and rMic files back into \Snapz Pro X
11:24am done

Fang – Mike Seyfang



About mseyfang

Interruptus Digitalis
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One Response to A ‘boy scout’ approach to recording Skype group video interviews

  1. Pingback: Biodiversity ‘Arks’ – anatomy of a Nature paper « The Environment Institute

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