DV Camera Passthrough vs TV Tuner Capture

[rkr1958]

I have a Avermedia TV tuner card hooked up to coax-cable that I use to capture TV programs. I also have a VCR that I've use to capture my VHS movies (for backup) by VCR via RCA cable ==> DV Camera ==> DV passthrough via Firewire ==> Computer.

I wasn't happy with the ability of my TV tuner card to tune to certain channels. They were noisy. So I thought that I'd use the tuner on my VCR. I did this by running the coax-cable to the VCR then coax from the VCR to my Aver TV tuner card. The quality of the TV was greatly impoved.

Now, I though why don't I just capture my VHS movies using the coax instead of the DV camera passthrough. However, the quality of the capture was significantly degraded using the coax. Even using Huffyuv 720x480 I noticed a significant and poorer difference versus using DV passthrough.

I guess the DV camera via the RCA cable does a better job in the anlog to digital conversion than does the TV tuner. Also, now if I want a quality capture of a TV program I can use the DV passthrough method.

I justed wanted to share my obsevations. Do they make sense?

[upshot]

Are you using quality coax cables? Do you have a power filter?

My guess would be this is where your problem lies...

[Richard_G]

They make perfect sense, think about it. You are starting with a video signal in the VCR, either from a tape or from the tuner and you then have two choices. Pass that video signal to your DV camcorder where it is converted to data and transferred by Firewire to your hard drive. A single conversion step.

Alternatively, you start off with the same video signal, pass it through a very cheap and crude radio frequency modulator to turn it into a radio frequency signal (also converting any stereo audio that you may have had in the first place into mono). You then pass this through a length of coax cable to an equally cheap low quality radio receiver (the tuner on your TV card) which converts to back into video. Your computer then converts that video signal into a data stream (in whatever format you have chosen) and it finally ends up on the hard drive. Three lots of conversion.

Is it really surprising that the quality is better with passthrough, particularly when you said that the tuner in the TV card isn't too clever in the first place?

[gadgetguy]

And using the command line functions of WinDV you can use Windows Scheduler to automatically capture the program unattended.

[rkr1958]

Thanks for all the replies.

Alternatively, you start off with the same video signal, pass it through a very cheap and crude radio frequency modulator to turn it into a radio frequency signal (also converting any stereo audio that you may have had in the first place into mono).

My VCR, which is a Sanyo VWM-800, keeps the stereo. I have no proof here, just observation, but I would venture to guess that the resultant signal coming out of the VCR's tuner output if good and realtively loss-less. It's this signal, which is anlog, that I feed either via co-ax to TV tuner or RCA via DV camera & firewire to my PC.

Your computer then converts that video signal into a data stream (in whatever format you have chosen) and it finally ends up on the hard drive.

I believe you hit the nail on the head here and this is the crux of the quality difference. When I go co-ax it's the TV turner card that converts to anlog signal to digitial. In the DV passthrough it's the DV camera that does the conversion. The firewire tranfer is a no-loss, given no drop frames, one-to-one transfer of digital data.

Are you using quality coax cables?

I believe so. The TV looks "good" when playing on my PC using my VCR tuner.

Do you have a power filter?

What is a power filter? I guess I'm not using one ...

And using the command line functions of WinDV you can use Windows Scheduler to automatically capture the program unattended.

I'm using VirtualVCR for my TV captures. If I remember correctly, I do believe there is a scheduler for that. However, the thing I must remember to do, whichever method I use, is to set the schedule to record from channel 4 if I use the VCR's tuner. Also, I need to make sure that the VCR is on the channel I wish to record.

[gadgetguy]

I'm using VirtualVCR for my TV captures. If I remember correctly, I do believe there is a scheduler for that. .

I tried VirtualVCR a long time ago but I didn't think it worked for firewire input. WinDV works for me.

I need to make sure that the VCR is on the channel I wish to record

Quite true, so it becomes problematic if there's more than one show that you want to record and can't get back to change the channel between them. However, it's possible by putting a tape in the VCR and scheduling it to record the programs as well. (Just make sure their clocks are in sync.)

[rkr1958]

Quite true, so it becomes problematic if there's more than one show that you want to record and can't get back to change the channel between them. However, it's possible by putting a tape in the VCR and scheduling it to record the programs as well. (Just make sure their clocks are in sync.)

Great suggestion ... Thanks ... That should work, as you metioned, as long as the clocks are in sync.

EDIT: Also, I wasn't familar with WinDV. I just looked it up and downloaded. It looks like a hand little progam. Thanks.

[Richard_G]

Thanks for all the replies.

Alternatively, you start off with the same video signal, pass it through a very cheap and crude radio frequency modulator to turn it into a radio frequency signal (also converting any stereo audio that you may have had in the first place into mono).

My VCR, which is a Sanyo VWM-800, keeps the stereo. I have no proof here, just observation, but I would venture to guess that the resultant signal coming out of the VCR's tuner output if good and realtively loss-less. It's this signal, which is anlog, that I feed either via co-ax to TV tuner or RCA via DV camera & firewire to my PC.

If you output from RCA cables to DV camcorder you aren't using the modulator at all, you are taking the video and stereo audio straight from your source tape or from the tuner in the VCR. In this case the stereo audio will remain. If you use coax you are passing the video and audio source via the modulator and ending up with a radio signal but generated by a very crude low power transmitter that isn't capable of encoding stereo audio. The tuner on your TV card is almost certainly capable of receiving stereo audio from a TV transmission, it's just that you'll never find a VCR modulator that can generate one. If you ever get the opportunity, have a look at the output of a VCR modulator on a spectrum analyser and compare it with an off-air TV transmitter and you'll see just how bad it is!

Of course, there is always the middle way. Use analogue video and stereo audio from the RCA connectors and put that straight into the inputs on your TV card/sound card. You can then do an analogue capture that bypasses the two stages of conversion in the modulator and TV tuner and capture to whatever format you choose using whatever codec you choose. Personally, I gave up using this method as soon as I had DV passthrough as an option. Best quality, minimum grief!

[gadgetguy]

Personally, I gave up using this method as soon as I had DV passthrough as an option. Best quality, minimum grief!

Amen

[FulciLives]

Maybe I missed something here (I read this rather quickly) but you can use your VCR as a tuner but output via the standard RCA video and audio jacks to your Avermedia card.

I have an Avermedia AverTV Stereo and the capture quality is very good but you can't use the coax input you have to use the RCA composite or S-Video input.

The tuner is poor quality so yes you will get better quality using a VCR as a tuner.

Also coax cable for video is shit so this is another reason why the VCR to Capture card connection should be with composite or S-Video.

NTSC DV is crippled by the 4:1:1 color sampling. No such problems with the Avermedia (or most PCI type "TV Tuner" type capture cards).

I belive PAL DV does not use 4:1:1 but the DV codec is still a lossy codec. You would be better off using HuffyUV with a quality PCI capture card.

What Avermedia card do you have?

- John "FulciLives" Coleman

[rkr1958]

Maybe I missed something here (I read this rather quickly) but you can use your VCR as a tuner but output via the standard RCA video and audio jacks to your Avermedia card.

That was too obvious ... I missed that completely.

I have an Avermedia AverTV Stereo and the capture quality is very good but you can't use the coax input you have to use the RCA composite or S-Video input.

Also coax cable for video is shit so this is another reason why the VCR to Capture card connection should be with composite or S-Video.

NTSC DV is crippled by the 4:1:1 color sampling. No such problems with the Avermedia (or most PCI type "TV Tuner" type capture cards).

So if I understand you correctly my capture using RCA from the VCR to my AVERTV Tuner Media card should be as good or even better than using the DV camera passthrough? Wait a minute ... I just check my card

What Avermedia card do you have?

It's an AverTV Media PCI tuner card. It doesn't have RCA inputs. Just co-ax, looks like S-Video. Also, there appear to be two audios but I'm using one as a crossover between the TV turner card and my sound card. I'm going to have to pull out my documentation on my TV turner card and figure out exactly what I have. Great suggestion though on the RCA cable.

[pchan]

rkr1958,

I used to have problem with Hauppauge WinTV card poor signal reception. When you scan your TV channel, try set to antenna instead of cable TV. For me, it improves a lot. This is what the test suggested to me.

[FulciLives]

My Avermedia capture card has composite video and S-Video inputs.

If your card only has S-Video input then chances are it came with some sort of adapter with a female composite jack on one side and a male S-Video jack on the other side to convert a composite singal to S-Video for input.

You can also buy such connectors at Radio Shack or you could buy a cheap S-VHS VCR to use as a tuner then use the S-Video output on it.

I wish I could give you more info but I am not familiar with that particular Avermedia capture card.

- John "FulciLives" Coleman