Archiving from MiniDV back to MiniDV...

[Boyan Dob]

Originally Posted by Mike McCarthy

For comparison, we export our display masters at 720p24 into WMV at 6Mb/s and they look fine when we play them on our 720p projector in our edit theater, so 4Mb/s should be more than enough to backup DV quality footage. WMV is a very efficient encoding scheme, and the numbers should not be compared with DV. Compared to HDV, which is 6 times the frames size at 25Mb/s, SD at 4Mb/s is a similar data rate per pixel. You will lose quality that you wouldn't lose in DV, but you should still get decent results for most intents and purposes.

Well, the "problem" with my material is that I record sports. Most are of indoor volleyball and lately golf.

In BOTH cases quality matters a lot when doing slow motion to analyze actions...

At first seeing that videotapes are in interlaced mode and that it's very hard to make a good progressive mode made me disapointed with the "technology", and thus it was even more surprising for me to discover that interlace mode can, with proper deinterlacing, give me twice more frames!

So, instead of having just 25fps I now have true 50fps, and swings in golf are now much clearer to see/analyze as are hits in volleyball!

I use Avisynth script with line "SeparateFields" to open AVI/WMV files in VirtualDub which doubles the framerate but gives me just half of picture height, but then I use VirutalDub filter "deinterlace - smooth" from Gunnar Thalin which makes picture in full height and moreover the imge is even sharper than if I use default height without separating fields... For me it's a little incredible discovery indeed! (I once searched for consumer videocams which record on 50fps or more and had no luck, and I guess not even today there are videocams which record at high framerates, which is very important for sports/slow motion! Even worse, I guess than new HD videocams have only progressive mode and no interlaced mode anymore, which means that there is no way to get 50fps as I can now.)


The thing is that if I comapre video in WMV coded to DV codec the quality of frames in WMV is just much worse than DV, for example, when you swing a golf club with high speed then shaft itself becomes blured and almost invisible, in WMV this effect is way more notable than in DV format!

At the moment I am trying out all lossless video codecs I was able to find (5 of them) and will see what happens... I'll also try Xvid and WMV codecs at low compression and see if I still keep the quality of frames so I can have sharp image in 50fps mode as I can with DV codec...

I'll post my results.

P.S. If anyone is interested I can also make few screen captures and show the difference between 25fps vs. 50fps deinterlacing with WMV/DV codecs.

[Mike McCarthy]

"You will lose quality that you wouldn't lose in DV, but you should still get decent results for most intents and purposes."

Statement still stands, but you are clearly one of the few exceptions. SlowMo requires the maximum available quality.

Don't waste your time and disk space with "Lossless" codecs. If the footage is already on MiniDV tape, capturing to the DV codec is a Lossless process, and no other codec will even come close in terms of disk space. The "Loss" from DV has already taken place on the tape, so a direct copy of that to the hard drive will not lose any more data. Any new Slowmo Renders that you make should not be to DV, but to a truly Lossless codec for maximum quality.

[Ervin Farkas]

Boyan, I did some testing with DivX a few years ago: took a 90 minutes movie from a DVD (an action packed drama, The Transporter), compressed it to a 700 MB CD and played them both in a blind test from my computer on to a 50 inch plasma display - no one was able to tell the difference. It was an old version of the DivX codec, and I used DrDivx to encode, tweaked some options. It's an amazingly efficient codec!

So you should be fine burning 60 minutes of video to a CD in DivX format. If you intend to edit later, you might want to compress to a 4.7 GB DVD instead, you will really be able to retain full quality. In my opinion, no other codec comes even close to DivX - too bad it is not adopted by the industry.