DIgital/Analog conversion question...

fosko wrote on 10/25/2005, 9:33 AM
I have a digital source. It has RCA/composite outs. I want to take the source and bring it into my computer to write to DVD. I know the dvmc and some other devices will do this. My questions:
1) is composite a digital or analog signal. if it's converting to analog I'm guessing it's losing some quality. Is there anyway to maintain that digital quality ?

The reason a co-worker and I thought it might NOT be analog is because most HDTV's have the 3 composite inputs. I would like to find a way of keeping the quality digital..but if the only output is converting it to analog I guess it doesn't make much of a difference. Conversaly..if the output is digital, I'm assuming something like the ADVC would work.

I also have a Hauppauge USB device that will do the job.. but don't know about the quality.. will try it out.

Finally... there is a coaxal out..I have a vidio capture card with coaxal in...will that bring it in digital ?

Thanks !

Comments

JohnnyRoy wrote on 10/25/2005, 9:51 AM
Without knowing what device this is and looking at the specs it’s hard to say what its output capabilities are. In general, composite outputs are analog as is coax. The device would probably have a firewire output for digital transfer. I would not use coax or the Hauppauge. I don’t think you’ll get acceptable quality.

You could use an analog to digital converter like the ADS Pyro A/V Link or Canpous ADVC-110 to bring this into your computer via composite to firewire as DV AVI file. This is not a digital transfer (its analog).

If you’re not going to edit the footage, you can capture it directly to a DVD compliant MPEG2 file with something like the ADS Instant DVD 2.0. In fact Instant DVD 2 will do direct-to-disc DVD recording bypassing your hard drive. I have both the ADS A/V Link and ADS Instant DVD 2 and recommend them highly.

~jr
Blues_Jam wrote on 10/25/2005, 10:34 PM
Since in one place you mention "RCA/composite outs" (plural) and in another place you mention that "most HDTV's have the 3 composite inputs" it appears you may simply need to have some terminology explained to figure out what you can and want to do.

Since you don't say what your "digital source" is I'll just give some general definitions:

1) Composite video uses a single cable with RCA connectors. A single conducter carries all video information combined (composited) together. This is the lowest quality video output and is comparable to VHS.

2) If what appears to be a coaxial output is actually a coaxial out then there is likely a coaxial input as well. If this is the case then the coaxial output is generally used as a pass-through for cable television input.

3) If what appears to be a coaxial output actually has 4 pins in the connector then it is what is called S-VIDEO out. S-VIDEO separates the chrominence (color) and luminence (brightness) signals and provides a significantly improved output over composite video.

4) Component video (not to be confused with composite video) separates the video into three (3) different elements (2 for color difference information and 1 for luminance) and uses 3 separate cables with RCA connectors. This is the highest quality video output.

ALL of the above video signals are analog. If you capture (analog to digital conversion) the COMPONENT video out then any losses will be due to the quality of your capture hardware, software, or methods and not the quality of the output signals.

Also note that there is no audio information contained in the video outs so that correct audio connections will have to be made if audio is desired.

Blues

EDIT: For completeness, cable companies now also send digital information over their lines but even so the output on the coax out will be that of the coax in and not what is being played on the device.
fosko wrote on 10/26/2005, 12:36 PM
Thank you Ronny Roy and Blues. That has helped me understand a lot better. I've checked and output source (my digital cable DVR box actually) has a lot of output..most of which I beleive are disabled. I know the Coax works, and I beleive the S-Video works. THere is also component (I know now it's NOT composite) out which I'm pretty sure is enabled. My hopes was to get the signal into my PC and be able to have digital quality. I don't think that'll happen because of my limited options. It looks like now i can either take it in Coax..or maybe S-Viceo if my card has s-vid in (I'll have to check). From what you'r saying either one should be acceptable quality. All I want to do is watch the Simpsons and free up some disk space on the DVR.

It would also be great if my video card has video out...so I don't have to set up a monitor...just video out into the TV to set up the Vidcap. (this PC will be dedicated to this).

Actually.. the OPTIMAL would be if I could some how get it to feed into my lap top. it's got a burner and easier to do everything from there. But I can't figure out how to accomplish that. The converters I've seen all take composite imputs.. not component. The only possible way is if the s-video outpot is enabled I can find a device that goes s-video to firewire...Kinda thinking out loud here.

Thanks again.
fosko wrote on 10/26/2005, 1:32 PM
Hey Blues,
A question about your edit. Wouldn't the coax out be what's on the device...since what's playing on the device is what would show on my TV.. wouldnt that also come thru to my computer ?

Would the same hold true for the s-video out ?

Would'nt it go from cable in--to tuner in box--to coax/s-video/or component out ?

Know of any boxes that will convert from Component out to FireWire ?
farss wrote on 10/26/2005, 2:25 PM
Several boxes that'll go from component to firewire or even directly into the PC. The SD-Connect from Convergent Design will do this in SD, Black Magic Design have quite a range of cards and boxes that cover both SD and HD, hope you've got deep pockets and a fast PC though.
If you're trying to record HD or SD off DVB broadcasts much better to buy a tuner card for around $100 and record the native mpeg-2 stream, it's all digital that way.
Bob.
Blues_Jam wrote on 10/26/2005, 10:22 PM
"A question about your edit. Wouldn't the coax out be what's on the device...since what's playing on the device is what would show on my TV.. wouldnt that also come thru to my computer ?"

In this case, YES, except that you must remember that the connection is made to your TV's tuner and the TV must be tuned to either channel 3 or 4. This means that what comes out of your cable box at that point contains ALL of the video and audio on a CARRIER wave just as if it were broadcast from a television station antenna.

I wouldn't be concerned about receiving digital quality signals if I were you... even on your "digital" cable box only the channels above 99 are actually received digitally, below are actually analog anyway (except for possibly channel 1). Just as a note: Sattelite TV is 100% digital.

Blues

ricnev wrote on 10/27/2005, 2:53 AM
Just a slight correction here - there are still something over 80 analogue satellite TV channels still broadcasting over Europe. I don't know about the rest of the world.

Ricnev.
JohnnyRoy wrote on 10/27/2005, 6:07 AM
> Would the same hold true for the s-video out ?

If your cable device has S-Video outputs then that would be the highest quality to capture. Get the ADS A/V Link and capture via S-Video. It will be higher quality than coax.

~jr
fosko wrote on 10/27/2005, 8:51 AM
If your cable device has S-Video outputs then that would be the highest quality to capture. Get the ADS A/V Link and capture via S-Video. It will be higher quality than coax.


Higher than component ?
I'm looking at the ADS AV link...I beleive it does component and S-vid. and it outputs to firewire.. so I can use my laptop.. which is a preference.
JohnnyRoy wrote on 10/27/2005, 7:59 PM
> Higher than component ?

No, S-Video is not higher than component, but your Hi8 camera doesn’t have component out so its not an option. I was just recommending that S-Video is the highest possible capture for you Hi8 camera.

~jr
fosko wrote on 10/27/2005, 8:34 PM
thanks...
i calle ADS today about the pyro av... they said the DVD xpress was a better choice because the file size would be smaller.
it's also only $99
JohnnyRoy wrote on 10/27/2005, 8:51 PM
> they said the DVD xpress was a better choice because the file size would be smaller. it's also only $99

Yes if you’re not going to edit it and just burn it to DVD then DVD Express or Instant DVD 2.0 is a better option for you. You can even capture direct to DVD and bypass your hard drive completely. The Instant DVD 2 model is a little better but if all you want to spend is $99 then DVD Express will get the job done.

~jr
Blues_Jam wrote on 10/28/2005, 2:44 AM
Ricnev,

A slight correction to your correction or perhaps the word 'clarification' would be more appropriate since your statement is not wrong but it's implication may be misleading to some.

Though not all television broadcast stations are digital-capable, the satelite television provider (DIRECT TV, DISH Network) receive the signals, digitize them, compress them, and encrypt them before they transmit them to the satelite. The signals received on a home TV dish are 100% digital.

For more in-depth information on the entire process, howstuffworks.com has a very nice presentation of the whole thing at http://electronics.howstuffworks.com/satellite-tv.htm

Blues

fosko wrote on 10/28/2005, 7:33 AM
Actually... i am going to edit (edit out some commercials). But I don't see that being a problem. Will do it in vegas or some other software provided with the unit.
farss wrote on 10/28/2005, 7:54 AM
Editing mpeg-2 in Vegas isn't a good idea and it's pretty slow. It will do it but the mpeg-2 has to be de-compressed and then compressed again. Best bet is Womble, cheap and works pretty well.
If you're trying to record off air actually your best bet is a DVB tuner card, that'll record a native mpeg-2 stream, a bit copy of what left the station! Then edit that with Womble and use DVDshrink to knock the bitrate down to something within DVD spec. Actually most DVB cards come with some applications to do this.
Bob.