Capturing a mathematics lecture

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2007-12-18 , Capturing a lecture, Capturing a mathematics lecture, Manual Audio and Slide Capture, Automated Audio and Slide Capture, OpenOffice Slide Capture, Lecture browsing system.

1 Capturing a Mathematics Lecture

Some general comments were given on Capturing a lecture, as well as Manual Audio and Slide Capture. Here we are concerned with capturing a 'traditional' mathematics lecture, that is to say, a lecture that heavily depends on black boards.

2 Specifications

  • It needs to be cheap. (Cannot afford a production team for each lecture, or an automated lecture recording system.)
  • It needs to capture the content, but does not need to be visually attractive. (We operate under the assumtion that people viewing the lecture do so because they are strongly interested in the content.)
  • It needs to be non-invasive (the lectures arent given specifically to be recorded, but are recorded while they are going on for a live audience)
  • The content (speech and writing) needs to be captured as clearly as possible. (Maths lectures are often hard to follow, and details of writing are crucial. Audio needs to be good quality so that it's not a great strain to listen to.)
  • The lecture is delivered primarily by the lecturer writing on the blackboard, and lecturer will often not be able to use just one blackboard.

The last point requires a little of discusion: A mathematics lecture often uses all blackboards available, with the lecture being developed across all available blackboards in the course of an house. This is because mathematics proceeds progressively, referring back to previous results. Hence those results need to be visible. In some ways this rules out using a single electronic whiteboard or similar.

If the lecture could be delivered just using a whiteboard (or ohps), then this would make things easier. In the first case, the lecture could be captured electronically off the whiteboard. If delivered on OHP, a single camera could be pointed at the OHPs, recording OHP along with voice. This could be made available as video (or set of stills), and scans of the OHPs could be made available alongside the movie. This would be quite satisfactory in many ways. However, the case we're looking at here is one where the lecturer feels that it is absolutely essential to use all available blackboard space. (Or where allowing the lecturer to use all available blackboards is the only way of getting consent for recording the lecture.)

All the methods discussed below rely on a single person ('producer') being available to capture the lecture.

3 Method 1: Photographs + Audio

A digital stills camera is used by the producer to photograph whatever blackboards need photographing, e.g. every minute. The camera records the time at which the photographs are taken. At the same time, audio is recorded, in such a way that a timestamp is available at the end of the recording (alternatively, the first picture is taken when the audio is started, so that we can synchronise this way). Using timing of slides and audio, the two can be synchronised.

Total cost of system about GBP 500-1000. However, many of those components may already be available, and only some may need to be bought. Details (as of 2007):

  • Digital still camera
  • Audio recorder: e.g. Zoom H2, or Fostex FR2LE, see Audio Recording Tutorial
  • Wireless mic: e.g. EW112P G2 (be sure to get a G2 series as it uses AA, and can be used reliably with rechargeables)
  • Wiredbackup microphone
  • It may help to get a small tripod

You can then follow the procedure given on Manual Audio and Slide Capture. Except that you simply ignore the instructions about powerpoints, but you simply take pictures of the board as and when necessary. You'll need to find a compromise between the amount of images you need, and the amount of detail that might be lost between images.

The Sony ICD-CX50 voice recorder has got a camera built in, and can take pictures while recording. It's not too expensive, and has a mic in (automatic gain). The image quality may well be good (resolution is quad-vga), but what the audio quality is like remains to be seen.

4 Method 1 automated: ICTP EyA

The ICTP EyA system implements a combination of methods 1 and 2, and can be recommended if you need to record a lot of lectures.

5 Method 2: SD video

Standard definition video. If you have a large set of boards, and the lecturer uses all of them, then you'll need a producer in the room, who can follow the lecturers. If the blackboards are very wide, and the lecturer writes small, and across the whole width, you might need to split split in two by a vertical line down the middle. The remaining sections are small enough so that they can be captured in enough detail using standard definition video (e.g. 720x576 for PAL). The producers pans the camera between the sections of the blackboards, and audio is recorded onto tape.

If the lecturer writes large enough, and uses only a single set of sliding boards, you might be able to set up the camera in 16:9 (effective pixels 1024x576 in PAL), which may give you enough resolution.

In order to facilitate processing of the lecture afterwards, it may be best to capture the tape in realtime, e.g. using a FireStore FS-4 recorder, or onto a hard disk.

Total cost of system about GBP 2500-3500, as follows (as of 2007):

  • An SD DV camera (e.g., as of 2006/07!!, a Sony PDX-10, PD170 (good in low light), Panasonic AG-DVX100, or a range of more recent models). Rremember to get skylight filter to protect lense. You should get a camera that has good low light performance, and the PD170/VX2100 are known to perform well in low light.
  • Wireless Mic (g.g. EW112P G2)
  • External mic for backup: e.g. the PDX-10 comes with external mic, so none required. With PD-170 use any mic available. You could get something cheap, or a better mic, such as an ME66 or equivalent.
  • Tripod with fluid head. If you don't want to spend too much you could use a Manfrotto PRO55, with RC128 head. It's a high-end photographic tripod, and works quite well for video. It's not too bulky, and squeezes inbetween rows in a lecture theatre quite well.
  • It's good if you can capture on the fly. You could use a portable DV recorder for this (e.g. a FireStore FS-4 or similar). If you don't need to be mobile, you could capture straight into a laptop or desktop computer.
  • Tapes: You'll need one per lecture, should be less than GBP 2 per tape.
  • Headphones
  • Flightcase to put it all in, e.g. normal flight case or Storm or Pelicase for better protection
  • Disk space for processing: 13GB per lecture, e.g. at least 312 GB for a 24 h lecture course to capture all the material, and probably the same amount again for writing out the edited lectures.

Notes on tape length/XLR: Tapes will typically last 62 minutes on SP.

  • Sony cameras: Generally their cameras either don't do both LP and XLR in.
    • The PDX10/PD170 has XLR, but don't have LP, so 62 minutes all. So need to make sure that lectures are 62 minutes or less. Not a problem for strictly timetabled course lectures, but may be a problem for distinguished lectures.
    • Another alternative is to get a VX2100 and then add a GlenSound unit for XLR input ('BBC sound mod'). The VX2100 has LP, which gives just over 90 minutes per tape. On the other hand, if a FireStore is used, the camera tape is really just for backup. Note that long-play tapes don't age well.
  • There are non-Sony cameras can do LP as well as have XLR in, e.g. the Panasonic AG-DVX100, which would be a good candidate for lecture filming. (Note however, that the low light ability of the VX2000/2100 is simply unsurpassed, although the Panasonic probably comes close.)

6 Method 3: HD video

High-definition video. Using a high definition camera (HDV), you'll get better resolution. Where you are filming lectures of a single (set of sliding) boards, you might have enough resolution.

Cost of system: As for previous option, but greater price for the camera, e.g. Sony Z1. (Need to get a FireStore-like recorder capable of HDV, or an HDV capture system.)

You might be able to use a Sony V1 to capture the whole lecture as progressive HDV, which would save you deinterlacing, and thus gets your higher resolution more easily. (In principle, on non-moving areas, with a good de-interlacer, you'd get similar quality with the Z1, but using a V1 straight away will remove that extra work.) This remains to be investigated.

7 Method 4: Multi-camera

Multicamera capture is always an option, and you could set up an Anycast system to do this. It's expensive (say several GBP 10k), but it will give you good quality, but you'll need to have somebody there to operate it. You'll only need one person to operate. More notes on Tutorials/Multi-camera production.

8 Non-camera based capture

For instance, can you use a electronic white board running a capture application to record the lecture? In principle, this is a very interesting option. Most mathematics lectures require more than one board to be delivered effectively, and I am unaware of an electronic white board system that lets you combine various boards.