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ARSCLIST  December 2016

ARSCLIST December 2016

Subject:

Re: Somewhat OT: Digitizing videotapes

From:

John Schroth <[log in to unmask]>

Reply-To:

Association for Recorded Sound Discussion List <[log in to unmask]>

Date:

Wed, 14 Dec 2016 01:19:46 -0500

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (182 lines)

Hi Joel:

My two cents here as I do this for a living....

I would be hard pressed to send your one-of-a-kind tapes to any chain. 
I've heard of one horror story after another.

For all the reasons you mention below and more, I would only go to DVD 
as a second/reference media in conjunction with the master file. Ripping 
files from DVD is a poor substitute for going directly to a higher 
quality file-based format in the first place. File based format is the 
direction everything is headed. You want multiple copies of the files 
stored in different physical locations. I don't like cloud or other 
services, I like to be in control of my own destiny. If you have 
checksums made of the files while on the original capture drive, and 
move the checksums with the data, you insure no data corruption. Then 
run the checksums on a regular basis (every 6-8 months) on each copy 
drive to insure the drives still hold the data without any data 
degradation.

In analog video, there is no "metadata" that holds the original date and 
time, so there is no way to capture this as part of the file.

Insure the analog video is digitized properly and with the right 
equipment. Multiple options for playback decks allows one to see which 
tapes best play back in the best deck. The analog video signal should be 
properly set up and adjusted (using scopes and processing amplifiers) 
and properly processed with the right time base correction to insure the 
analog signal is as stable and clean as possible before you digitize. 
Picture instability, color noise, etc is "baked" into the digital 
version during digitization and it is very hard to correct for after you 
have digitized. Choosing the right codec and compression levels for your 
needs is key. The less compression, the more you can do with the content 
and the better the content will migrate to new formats in the future.

Some camps will say uprezz now. Some like myself, say to stay as close 
to the original format as possible - the same image ratio high by wide 
as possible, holding the essence of the original analog format 
(interlaced, not progressive and at 29.97pfs). Color sampling rates are 
important. You want as much color information as practical (based on the 
original format). Better to have the highest quality standard-def 
interlaced file that you can afford to store now. There will be both 
hardware and software solutions down the road that will do a much better 
job at uprezzing and de-interlacing than can be done today.

There has been recent discussion about this on the AMIA list-serve 
recently. Below is the answer from Jim Linder who really knows his 
stuff, when your same question was asked. Hopefully he does not mind 
that I quoted him.

Good luck,

John Schroth
MTS

"Fortunately in analog encoded (as in NTSC) there is a good answer if a 
bit technical. I am going to try to give a short, coherent, and 
understandable answer - but there is a great deal of in depth technical 
information on this subject available elsewhere and if others want to 
discuss it off list I am happy to.

We need to go back a bit and look at the development of NTSC and how the 
color information was added or encoded into the black and white picture. 
The standard adopted by the FCC mandated that those who had a black and 
white television would not have to throw out their old tv in order to 
get color. Color information had to be encoded into the black and white 
signal - the black and white televisions would basically not see or 
ignore the encoded information, and color sets would see what is called 
"burst" which is essentially a signal to turn on the color decoding 
circuitry and to decode the color information and apply it to the 
signal. This burst signal is also called subcarrier and is of a specific 
frequency. The color information was encoded based on the phase 
relationship of the subcarrier during the period of time of the line of 
active black and white information. Remember this is all analog and 
based on time / frequency and amplitude of a signal. The phase of the 
subcarrier signal contains the color information.

If you think of this phase relationship you realize that it takes a 
certain amount of time to change from one phase relationship to another 
- so color changes that are "nearby" or close to the previous can be 
done in plenty of time, but ones that are 180 degrees out of phase 
actually take a bit more time. During the time that the phase is 
changing, you actually do not know what the color is at all. Normally 
and in analog this is not an issue because your eye cant see such a 
small part of the line, except in extreme circumstances such as when 
someone is wearing a herringbone jacket or very intricate patterns with 
different colors. When this happens we actually see noise or moire 
patterns because the decoding in the set can not change fast enough and 
so you get visual artifacts.

So, the practical limit to the horizontal resolution in digitizing an 
encoded SD signal (like NTSC or PAL) relates to the burst frequency and 
the time available. If you sample higher then the frequency of the 
information that it was encoded in, you are generating noise and 
visually the signal can actually look worse. A great deal of 
experimentation was done to determine what actually is optimal and 
certain digitizations systems that were built actually considered this 
so that there was no "oversampling" and thus the reduction of quality 
and the adding of chroma noise in the picture.

There is another factor and that has to do with the chroma decoding of 
the encoded signal. There are several kinds and some are better with 
certain signals with others. There are comb filters that remove specific 
frequencies in order to present a cleaner lower noise signal and 
adaptive comb and other filter types that are all designed to reduce 
noise and artifacts.

So you do not digitize in the highest resolution possible - you digitize 
at the optimal resolution and with the optimal chroma decoding to get 
the cleanest and most accurate representation of the original analog 
signal. Fortunately this technology has been available for some time and 
a great deal of video preserved has used this technology and is now 
happily in files."
On 12/11/2016 9:37 PM, Joel Bresler wrote:
> Dear friends:
>
>   
>
> I would like to digitize some camcorder footage. A few questions for anyone who has tackled a similar project.
>
>   
>
> First, there are plenty of services (Costco, etc.) which will digitize tapes onto DVDrs. I am wondering in this age of increasingly cheap storage if it makes more sense to go from tapes directly to digital files instead? (Avoids any quality issues going to DVD first and then ripping to digital; avoids issues with suitability of DVDrs for archival storage; renders video in editable, digital form right at the start.) Are there any suggested services that take this approach?
>
>   
>
> Second, any suggested quality level for the video? Is there any need to preserve it at a higher resolution than the original?
>
> Third, suggested ways of storing the digitized video? (RAID array? Backed up on Amazon Web Services?)
>
> And last, is there any way to capture date and time metadata on the transferred video? WITHOUT showing it continually on screen as the video plays?
>
>   
>
> Thanks in advance for your insights!
>
> Regards,
>
>   
>
> Joel
>
>   
>
>   
>
> Joel Bresler, Publisher
>
> www.sephardicmusic.org
>
> 250 E. Emerson Road
>
> Lexington, MA 02420
>
> United States
>
>   
>
> 1-781-862-4104 (Telephone & FAX)
>
> [log in to unmask]
>
> IN CASE OF VERIZON EMAIL PROBLEMS, PLEASE USE MY BACK-UP EMAIL:
>
> joelbresler-at-gmail.com
>
>   
>
>   
>
>   
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 2016.0.7924 / Virus Database: 4728/13577 - Release Date: 12/11/16
>
>
>
>

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