Important questions about how DV and MJPEG react from sources, Please give an opinion

[Phire]

Please bare with me, I don't know much about DV which is why i'm asking my questions here:

1. If a person were to capture from his DVD player via analog into a DV card with analog input, at 720x480 how much quality loss would there be?

2. How efficient is DV's compression? becuase the DC30+ does a datarate of 6500 while the DV cards are usually a datarate of 3600. A friend had told me that DV may come out better becuase of how efficient it captures the video data.

3. Which is the cheapest DV card out there with analog input.

4. What would it take to compress YUV2 to DV in realtime?

Thanks for listening, and please try to give me some input.

[DrMordrid]

BEAR or BARE?

With one I answer questions. With the other we grab the girls and head for a nudist colony ;-))

1. The quality of DV inside the cam is excellent and it imports by IEEE-1394 without losses.

With analog capable DV cards you often capture 704x480 within a 720x480 frame, so there is a black 16 pixel border at the left. This is inconsequential as it's in the overscan area and can be cropped if necessary.

DV image quality after editing depends a lot on the specific codec used. They are not all the same. The Microsoft DV codec is junk because of color shifts and artifacts when it's recompressed, which happens all the time during the editing process. Unfortunately many cheap cards use the MSDV codec. The Canopus and RT-2000 codecs are among the best with no color shifts or artifacting.

In terms of inherent quality losses there will be one: analog video, such as MJPeg or MPEG-2, uses a 4:2:2 colorspace while DV25 (the consumer DV format) uses 4:1:1 (NTSC. 4:2:0 for PAL).

For 90% of uses this means little, but if you're doing bluescreening or other keyed effects it can make things problematic. High quality lighting helps, but you can't put back what ain't there. This can also affect compositing and overlays.

This is why it's often handy to have a system that can do two forms of compression, like the RT-2000's ability to handle both DV and MPEG-2. MPEG-2 has a 4:2:2 colorspace.

2. Efficient? It fits excellent quality, within the limitations of it's 4:1:1 colorspace, into 3.6 megs/second. That's pretty darned efficient in my book.

With DV imported by IEEE-1394 from a digital cam you get excellent quality, with some variance for the individual cam. Since DV also has basic error correction capabilities the better DV codecs can be recompressed a few generations with very little loss of quality. The only real problem is that of the colorspace and keying.

3. Right now VideoGuys has the Canopus DV Raptor and a very good software bundle going for $500. You get the DV Raptor with your choice of Premiere or MediaStudio 6.0.

http://www.videoguys.com/raptor.html

The next price level gets you a Matrox RT-2000 for $1200, and that includes not only DV analog and digital in/out but MPEG-2 as well.

Lets also not forget that post TI referred to on the main page stating that the RT-2000 2.0 driver set will be posted in Q3 with tons more capability. Interesting post....

http://www.videoguys.com/rt2000.html

4. It would take an analog card capable of piping YUY/YUY2/YUV to a soft DV codec capable of being piped to. In addition my guess is that it would take at least a PIII/700+ to do full frame compressions in realtime. I'd just get the Raptor or RT-2000 and save the headaches.

No matter what card you get stick to the hardware recommendations, especially those for the mainboards. These cards don't tolerate inefficient boards with sub-optimal PCI bus performance.

Dr. Mordrid



[This message has been edited by DrMordrid (edited 19 May 2000).]

[dgcom]

Hi!

I think, It would take at least 1.5GHz Pentium III to compress DV in software realtime.

My tests show that on P III 517MHz, it takes about 43 seconds to compress 10 seconds of video. In RGB. So, using the fastest codec to compress YUV2 could be aproximated to the number I mentioned.

Most of the DV cards with analog input (NOT ALL of them!) use it just for preview overlay.

The best way to convert analog to DV would be using either Sony DV camcorder or their converter box. Sony DV camcorder, when placed in appropriate mode can produce compressed DV strem over FireWire from it's analog inputs.

But, in any case, you can get problems with Macrovision when dealing with DVD set-top boxes.

Why don't you use all those ways to copy MPEG-2 from DVD to HD and THEN convert it to DV offline? Quality would be much better...

DGCom

[Phire]

"Most of the DV cards with analog input (NOT ALL of them!) use it just for preview overlay."

Hehe sorry I dont really understand that technical term "preview overlay", But does that mean I cant capture with it?

I had read at Videoguys.com that the DV Raptor had analog inputs, so this would probably be the best solution for me considering it costs only 500$. Am I right?

"Why don't you use all those ways to copy MPEG-2 from DVD to HD and THEN convert it to DV offline? Quality would be much
better..."

Well I wasn't really going to do that, I just wanted to know how much quality loss there would be that and to see how good the card can handle it.

And that sony device is like 400$ i think, So im probably better off buying the DV Raptor i think. In the end, i'm really just trying to find the best card for a reasonable price.. The most i'm willing to spend is 800$ and im stuck between buying a DV card or The DC30+ which does a 6500 datarate with MJPEG.

[DrMordrid]

Yup, that's right. The Raptor bundle at Videoguys is an excellent deal. I know several folks with 'em that paid a lot more and are very happy.

Dr. Mordrid

[dgcom]

"Preview overlay" is a function, when you output DV video back to camcorder (!) and what camcorder produces (analog video) is showed on your PC monitor - just "like" preview in analog capture, but synced with DV output. And it does not mean, you can capture this video.
Go to http://www.fast-multimedia.com and get DV.now manual - it will show how this setup works.

Even if you'll get DV Raptor analog capture work, it won't allow you to capture in DV format! It will probably be plain RGB.
Unless you have MiniDV camcorder, Raptor is worthless for you.

So, we have two options to produce DV video:
- realtime hardware capture (camcorder, converter or RT-2000)
- offline - using software DV codec in something like VirtualDub.

DGCom

[This message has been edited by dgcom (edited 20 May 2000).]

[Grigory]

Hi!
Several notes.

RGB to DV compression actually requires 1800 CPU, which is not available ... yet.

Surprisingly, I get 10 FPS with mpeg1 to DV recompression in VirtualDub fast recompress mode (4:2:0 YUV data from mpeg1 go to DV PAL 4:2:0 very well) on dual celeron 500 PC. One CPU is not busy, though.

You can use Raptor to do analog captures with lossless HuffY codec. It typically compresses full size RGB or YUY2 (and from DV in software) to 9-10 MB/sec data rate.

Correction: MPEG2 may have 4:2:2 or 4:2:0 colorspace, but DVD mpeg2 has 4:2:0.

My own tests show hardly visible qualuity drop on 5-th generation of DV. I used the clip with very complex content. It is very difficult to compress in any codec.
The contrast/brightness/saturation/color tone do not change, but I can see some noise in the movie of 5-th recompession.

Conclusion - use DV camcorder with Raptor to capture analog, or capture analog video with lossless codec and later convert it to DV.

Grigory

[JTurner]

Grigory, you said "Conclusion - use DV camcorder with Raptor to capture analog..."

Does this mean that you can play back an 8mm tape from an analog camcorder, output the signal over an S-Video cable into the input of the DV camcorder, out the Firewire port, into a DV capture card?
Would this be a good way to convert analog video to DV?
Does a DV camcorder's A/D convertor provide a DV stream when inputting an analog source via cable?

Please excuse me if these are silly questions. I don't own a DV camera.

-JT

[Grigory]

Hi,

I own digital8 camcorder that can play analog 8 tapes directly and produce DV data output.
It also has analog inputs that can be used to record from S-video or composite source.

When you insert IEEE1394 connector, it takes ownership on camcorder inputs, so the analog connectors switch to output only. You cannot record DV from analog on the fly. But ...
Using the tools that re-program camcorders, you can temporarily disable DV-in feature and use camcorder as analog-DV convertor on the fly, without recording this on tape.

All digital8 PAL and NTSC camcorder can do this. I do not know what models of mini-DV camcorders have these features.

I do not have 8 mm tapes with analog. My previous camcorder was VHS-c. So, I can either capture it output to D8 tape (not very bad idea, taking into account DV format video storage capacity of 14 G), or directly to hard drive with Raptor analog capture kit. Tape storage wears camcorder, but is very convenient as storage itself solution.
Direct captures to disk work well, but take a lot space.
In my case I can also use cheap TV tuner card for VHS quality captures. This is only necessary to convert remaining family video archive to CD ROM.

BTW, after one year I still have no problems with regular 8 tapes - they can store and play Dv video without defects.

This makes me thinking about D8 camcorder as a good middle-term video data storage device with cheap 14 GB storage units. Its price is also comparable or lower than for similar devices on the market

Grigory

[Phire]

Ok i'm going to get down to the final question, but BTW thanks for posting everyone.

I want a straight answer now

And before you answer this question, let me state that i'll probably never be using a cam. Mostly analog and possibly captures from DVD (AND YES I KNOW ITS BETTER TO DIRECTLY CONVERT DVD)

Would the Pinnacle DC30+ MJPEG at a 6500 datarate offer me better quality than a cam that recorded analog and then pushed into a firewire card? (Cam is better off probably anyway considering the convertor costs just as much, and the other cards are just way beyond my price range and go up to a $1,000)

And a question for Dr. Mordrid, a friend of mine wants to know which cards use the MS codec becuase he wants the best DV quality, he wants to know what the Studio DV/ADS Pyro use.