Capturing/digitizing video or stills

Easy version

  1. Use the Web interface to route the relevant deck to moviola. Moviola only has digital input, not composite. If it's a digital deck like the digibeta, then route directly by middle-clicking the deck and left-clicking moviola. If it's not digital, then you'll need to route through a transcoder like FS1 or FS2: middle-click the deck, left-click a transcoder, then middle-click that transcoder and left-click on the moviola item in the list on the right (under Computers).
  2. If you're making a movie and if you don't already have a directory on the /nle directory on moviola, make yourself one. That's a 30GB fast local disk array dedicated to video stuff. You need to capture to a local disk to get high enough bandwidth, don't even try using a NFS-mounted one.

  3. Start up the capture program on moviola from your /nle subdirectory. (It's also known as mediarecorder

  4. You can either capture movies or still frames. The movie icon is the leftmost one on the bottom left (the little camera), the still frame icon is the rightmost of those three (the face).

  5. In either case, you want to pick the Digital option under the O2 Video Hardware item.

  6. If you're making a movie, select Tasks->Movie->Video Production(JPEG) from the menus to create fullsize frames with hardware JPEG compression. You can use the Show Tasks Settings under the Tasks menu to customize the size and compression. I recommend that you use JPEG compression if you want nice smooth motion. Using any of the other (software) codecs or no compression at all will result in a jerky movie. I also recommend using the popular QuickTime movie format instead of the obscure SGI movie format, provided only for backward compatibility.

  7. If you're grabbing a still frame decide on the size (full, half, quarter) and format (SGI/RGB, TIFF, GIF, and JPEG/JFIF), either by picking something preset from Tasks->Image or going totally custom through Tasks->Show Task Settings.

  8. Decide what directory you'd like your saved files to be saved into. Use the text input box on top of the browser area on the right. Note that if you're saving movies, you should save onto local disk to minimize chances of missing frames.

  9. The record button is the little red circle in the lower right. If you're capturing a still image, just hit the button once. If you're capturing a movie, you'll need to hit the record button to start and the blue square stop button to finish. The screen will freeze briefly after an image capture. After a movie capture, more processing will happen, as shown by a dialog box.

  10. You can view saved images or movies from the browser on the right. If you doubleclick on a movie file, it will automatically play on the left. If you doubleclick on an image file, it will appear on the left. To return to previewing the video input source, hit the blue square stop button.

  11. You can change the default name if you want by clicking on the text. If you just keep clicking the record button, the filename auto-increments.

More detail

Additional notes

If you have already recorded an audio voiceover and you're sitting in the video lab recording a live video segment, it's often really useful to be able to hear the voiceover at the same time as you're running your live screen capture, so you can get the timing right. (For instance, you want to time it so that when you say the word "now" in the phrase "and now we see the foobar lighting effect" you hit some key that will have a visible result. I'm assuming you've already split the voiceover into scene-sized chunks in your audio waveform editing program.

The reason this is nontrivial is that digitizing live video at the highest possible quality takes all the CPU time and disk bandwidth on moviola. So playing back the audio files from moviola is not a good thing to do simultaneously with inbound video digitizing. And you can't play back audio files from radiance since its CPU is in another room and moreover it doesn't support audio playback. That leaves crossbar as the only SGI in the room which can safely emit audio. But crossbar is far enough away from moviola and the lab is loud enough that simply using its builtin speaker isn't very helpful, so you need to wire up its audio out into the audio in jacks on the IO panel and routed it through the mixer board into the main lab speakers.

Copy the relevant audio files over to the /tmp disk on crossbar. (You want them local to crossbar instead of playing off moviola's disks.) Then you can rsh to crossbar from the console on moviola and start up a soundplayer app that appears on the moviola console. It's safe to have the soundplayer GUI on moviola's console: it's not going to cause any resource contention, since the disk and CPU usage are all on crossbar. Then the digitizing person can just click two buttons on moviola's console in quick sucession (the soundplayer play button and the digitizing record button) in order to start things going.


If you're having trouble with dropped frames (i.e. things look jerky) when capturing video:

  1. Make sure you're using hardware JPEG compression. The software codecs will definitely drop frames. Uncompressed video is the worst of all, we definitely do not have enough bandwidth to get a 14MB/sec stream onto disk.

  2. You can tell capture to abort if frames are dropped while capturing a movie. It's a radio button under image in the Task Settings panel. This is much easier than doing the whole capture, and then eyeballing it.

  3. Make sure you're recording on to the local disk, not your NFS-mounted home directory. Moviola has a big local /nle partition just for video recording.

  4. You should turn off audio capture if you only care about video, since it's on by default and takes up bandwidth. Pick the "Do not record audio track" radio button under the Audio tab on the Task Settings panel.

  5. All of the above suggestions are lossless. You should be able to digitize fullsize video smoothly using the JPEG hardware. If somehow you're still having trouble and are desperate, here are some suggestions that will lower the quality of your video, but at least in a manner of your own choosing:

Tamara Munzner
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Last modified: Fri Jan 28 15:17:32 PST 2000