Analog Signal to Digital a Primer

Question

Many users have analog material sitting around, and they would like to get it into digital form, so that it can be edited. As this material is below SD (Standard Definition) quality, I will address the methods for digitizing it, so that it can be best edited in a DV Project. The output can be a DVD-Video, or other format, depending on what one wishes.
The process of getting this analog material into a digital form, is referred to as Capturing, and it is digitizing the analog material and writing it to a file, that can be edited.
One will need some method of getting the analog signals into digital form, and for connecting the analog output from their analog playback device to the computer. Though the analog signal could come from all sorts of devices, I’ll use a VHS tape deck in this example.
Since a VHS tape deck does not have an A-D (Analog to Digital) processor, and also does not have a a digital signal Out, one needs something in between it, and the computer. That “something” serves two needs: mechanical connection of cables and the ability to convert the analog to digital for use in an NLE (Non Linear Editor). That “something” can be a digital video camera with pass-through capabilities, a device, called a “bridge,” or a capture card inserted into a bus slot in the computer. All three have pluses and minuses.
The first two methods rely on one having a FireWire connection on the computer and will use the Capture module in the NLE software.
The digital video camera route is good, as one already owns it. Having one with pass-through capabilities is getting more difficult. The camera also has to have FireWire (FW, IEEE-1394a, or iLink) output, and the computer must have a matching connection.
An A-D bridge will do the same thing: allow one to connect the analog cables to one end/side, process the analog signals to digital and then output via FW to the computer. There are various such bridges available and two of the most often recommended makes/models are: the ADS-Pryo, and theCanopus/Grass Valley ADVC-110. Products, like the Dazzle lineup, just do not seem to work, or work well. I would avoid such.
A dedicated capture card performs the same task, with one exception. The card will mount into an empty PCI slot on the MoBo, and have inputs for the analog cables. The card will have chips on it, to digitize the analog signals and feed these to the computer via the PCI slot. These do not connect via FW, but have one drawback: they must, in virtually every instance, use additional software to do the actual Capture, as most NLE’s cannot directly see and work with them. Some of the included software Capture programs are better, than others. One common issue with many of these cards is a loss of sync, between the Audio and the Video. This is usually static OOS (Out Of Sync), in that it is usually off by a fixed number of frames, and does not drift over time. This can be fixed in the NLE, but is extra work. This ARTICLE will give you tips on correcting OOS.
Now, we are ready to begin the Capture, as our equipment and cables are all ready to go. We have a big decision in front of us - what format/CODEC do we use to Capture our digital files? Since we are doing an SD Project with non-HD (High Def) material, there is one fine choice: DV-AVI Type II w/ 48KHz 16-bit PCM/WAV Audio, using the DV/DVC CODEC. These files will be approximately 13GB / hour of Duration. Storage will need to be considered. These files are also I-frame, meaning that each “Frame” is rendered and available, so that frame-accurate editing is possible. The NLE will not need to do any processing, or conversion of these files, as even the Audio is ready for DVD-Video. Note: there will still be Conforming and the generation of PEK (Waveform Display) files, but the NLE will be able to do this quickly and efficiently.
Using AVI Uncompressed will get you nothing that you can see, other than larger files. Do NOT use any compressed format/CODEC, like MPEG-2, WMV, MOV, etc., as these will loose data from an already inferior source, and will then need conversion to be used, either with a stand-alone conversion program, or internally by the NLE. You loose quality and then have more work to be done. Do not let the temptation of smaller files lure you into using anything but DV-AVI Type II, and just accommodate the larger file sizes.
With the file format/CODEC decision made, the cables and devices hooked up, we’re ready to start the Capture. The exact operation will depend on what our equipment choice has been. See above for talk about additional Capture software, if one uses a capture card. Otherwise, we should be able to use the Capture module of our NLE. The first issue is that we will NOT have Device Control, as we would with a Capture from a miniDV tape-based digital camera, where we can control the mechanical aspects of the camera, during this process. As our VHS deck is hooked up to the A-D bridge, or digital camera w/ pass-through, via analog cables, our control signals cannot be sent to it. One would cue up the tape in the VHS deck, and then choose Record/Capture in the NLE’s Capture module, starting the Capture. Instantly, they would hit Play on the VHS deck, or via that deck’s remote control. This is easier the second time that one does it. I sit with the mouse in my right hand, poised over the Record/Capture button, and the VHS deck’s remote in my left hand, finger hovering over Play. It’s then a 1 - 2 push, and all starts. One can stop the Capture, if an unwanted section of tape comes up. The Capture module of the NLE will direct us on how to proceed from there, should more Captures be wanted. Some will just start up at a later point, and write an additional file for that portion of the tape, but some might require that one basically sets up a new Capture session One should investigate just what their NLE will require for doing multiple Capture sessions from one VHS tape.
When done, one closes the Capture module, and then navigates to the location that these DV-AVI Type II files have been stored in, and Imports them into the Project. This differs slightly from doing the Capture from a miniDV tape camera, as those Captured files are already in the Project.
Edit away, and Export/Share to the necessary output settings, file type and CODEC.
What about those VHS - DVD decks, the ones that will burn a DVD directly from the VHS tape? They seem so simple to use, and for the most part are. However, those DVD-Video discs, contain pretty heavily-compressed MPEG-2 AV streams. These MPEG-2's, besides being compressed, are in aGOP structure and are muxed (Multiplexed into one file with both a Video & Audio stream), plus there is often some Menus and navigation in the first VOB, the main container components of a DVD-Video. Many NLE’s can Import the VOB’s, and basically rip the MPEG-2 out of them, but that first VOB can be highly problematic, due to the way that most of those decks do the Menus and navigation. It is seldom 100% DVD-compliant by the DVD-specs. This can be a major problem. This ARTICLE will give you some background and tips on DVD VOB's.
Those dual-decks are good for doing one thing, regarding the DVD’s that they produce - provide one with an archival DVD-Video of the VHS tape, and not to be edited. However, the VHS side of these works well with an A-D bridge, just like a pure VHS deck does. I would strongly recommend that one does NOT use the DVD-Video portion of these, if editing will be desired. They cause many more problems, than they solve - just use them for an “archive” copy of the tape to a DVD-Video, for playback on a computer via DVD software or a set-top player, hooked to a TV.
What about film? Well, film is obviously analog, and one needs to digitize this to edit on the computer. The process of this digitizing is referred to as telecineing the film. While one can buy equipment to do this, it is expensive, and involves a lot of setup and testing to get the job done. There are many service bureaus, that offer telecining. Some are better than others. The main considerations are: care in handling of fragile film, how the telecining is done, i.e. frame by frame w/ a liquid gate, or just by straight projection, and then output format for the digitized files. Some of these services will offer a DVD-Video disc. Do not be tempted to do this. See above. Others will offer to write these digitized files to a miniDV tape, and this is just fine. One does then need a miniDV camera, or miniDV tape deck, to then do the Capture from, but the quality and editability will be preserved. The final delivery format would be to put these DV-AVI Type II files onto an external HDD. This saves one from having to do the Capture from miniDV tape, having to have a miniDV camera, or miniDV deck, and only Importing of those files would be required to get them into the Project. Many of these service bureaus will either sell you the external, or use one provided to them. Check out specifications for things like format of the external. FAT-32 will limit the file sizes to ~ 4GB max, and NTSF will have no such limitations. However, if the service bureau is on Mac, and you’re on the PC, their Mac’s can ONLY see FAT-32 HDD’s. Talk this over with the service bureau first, so that there are no surprises later on.
Hope that this helps,
Hunt
PS - also see this FAQ Entry for more detail.

Answer 1

the_wine_snob wrote:
 Products, like the Dazzle lineup, just do not seem to work, or work well. I would avoid such.
Although I now have a Canopus ADVC300 I previously used a Magix 'Movies on DVD' USB device. I found the results from this to be particularly good and, to my ageing eyes, I see very little quality difference.
I think this is because Magix use their proprietary high quality codec (from their Pro products) to capture the footage. Like DV-AVI it runs around 10GB+ per hour. This can then, very simply, be exported to DV-AVI Type 2 for use in PRE. Note that there are some sound synchronisation issues with the 'out of the box' settings - but the fix is quick and I posted details to the Magix forum.
Would I revert if I could return my ADVC300 bridge? Probably not - the firewire connection and the PC seeing the box as a camcorder adds to ease of use. In fact I am pleased to have both. There are some things Magix does better than PRE7 (batch exporting each scene as an individual DV-AVI file being just one) and it has smart-rendering which is handy for quick clip splitting/exporting.
Cheers,
Neale
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