Rez of DTV? Capturing 8mm/VHS at 720x480 on 1394, overkill

[john1290]

Few questions...... first, I have a low end Digital8 camcorder (Sony TRV-230?) that plays back 8mm tapes and works as a perfect DV passthrough for capturing stuff off DTV onto my system via firewire. I'm using the S Video/left right audio out from the DTV receiver and going into my camera and from the camera to the PC via the 1394 connector. When I capture stuff like that from DTV, I set my capture program to grab the video at 720x480 16 bit audio. I left my PC converting the 9 gig porn...er....NATURE movie to SVCD via TMPGEnc this morning. (I'll get home tonight and will see how big the resulting MPEG2 file is and what kind of quality it will yeild)....... am I capturing at to high of resolution for DTV? Forgive my ignorance, but what rez does DTV xmit in? What SHOULD I be capturing this at? If 720x480 is extreme overkill.....will this not provide better results anyway? I'm worried that if I capture at anything less than DVD spec and then compress it.....it might look worse than starting high and compressing. Feedback anyone???

Also......as for my old 8mm tapes (which were originally shot from a Sony Hi8 little camcorder...(2 years old?)....I wonder what rez THOSE were shot at? Is there a general rule of thumb fact that all camcorders like 8mm, Hi8 and old VHS camcorders record at 352x240? If so, to save space so I can burn these to DVD later and also don't clog my HD up, should I be capturing at lower resolutions since my source media was shot at low rez? Or should I just always capture at 720x480 and compress from there? I guess a good experiment would be to capture some stuff at 720x480 and then again at it's original rez (whatever it may be) and compress both and see which looks better...........any guidance/help/answers greatly appreciated!

Thanks!

[pacoreguenga]

Well, seems to me like you know the answers but want them from someone else.

First of all, DTV transmits multiplexed MPG2 streams through the waves, normally at 720 x 480. It depends on their capture / encoding hardware. DTV stations use realtime MPG2 capture hardware, with solutions ranging from $5,000.00 to $800,000.00 in many form factors. Most of them use CCIR601 full D1 (720x486) broadcast quality equipment all the way down their postproduction facility, and try to keep that resolution when their signal hit the waves.
However, not all the material to be aired comes from Digital Betacam or D1, sometimes it comes from Beta SP or even U-matic or SVHS!
Anyway, some rt encoders capture only at 720 x 480, or at 704 x 480. These are acceptable as DVD sources, of course. Audio is sampled at 44100 or 48000 Hz depending on the Station's equipment.
Your DTV receiver can fully decode and show you these signals at DV resolution (720 x 480), so you can feed your capture card at its highest quality settings securely.

Now let's talk about tapes.
VHS and 8mm can be captured at 352 x 240 as they aren't interlaced signals. This can be seen on rollers. (credits at the end of a movie) If you look close enough, you will notice black and color lines aternating.
SuperVHS and Hi8 share higher resolutions, as they are interlaced. This gives you effectively two fields for frame. They aren't really 720 x 480, but you can capture at that resolution, as they are close enough to it.

Now: If you capture at 720 x 480 from a noninterlaced signal, It will flicker! Unless you capture with a TV tuner card like avermedia's. They are really cheap (about $50 dollars)

[yg1968]

pacoreguenga,

He is using a DV passthrough (i.e analog to DV digital converter) which means that he has no choice but to capture at 720x480 because this is a set resolution for DV. With the exceptions of a few camcorders, DV is interlaced. Can't you just de-interlace it when converting to mpeg-2? Or is that even necessary? I am assuming that the analog to digital conversion feature of the camcorder automatically inter-laces the video when converting it to DV. Any thoughts on this?

Thanks

YG

[john1290]

Now let's talk about tapes.
VHS and 8mm can be captured at 352 x 240 as they aren't interlaced signals. This can be seen on rollers. (credits at the end of a movie) If you look close enough, you will notice black and color lines aternating.
SuperVHS and Hi8 share higher resolutions, as they are interlaced. This gives you effectively two fields for frame. They aren't really 720 x 480, but you can capture at that resolution, as they are close enough to it.

Now: If you capture at 720 x 480 from a noninterlaced signal, It will flicker! Unless you capture with a TV tuner card like avermedia's. They are really cheap (about $50 dollars)

So.....if I put an 8mm tape into my Digital8 camcorder and capture it at 352x240 and convert the raw AVI to DVD spec (720x480), it will look the same as say something captured from DTV (720x480 AVI) and converted to DVD spec? I fail to see how this would work....something tells me that even though my old 8mm tapes and VHS might have been recorded at a low rez....I should still capture at 720x480 to get the BEST pic quality possible when I do the DVD conversion. If my target was (S)VCD, capturing at 352x240 MIGHT be the way to go but since I need to take 4, 2 hour VHS tapes (my wedding) and throw it on DVD.....I think the capturing at 720 is the way to go even if my source is crappy, low quality tape. Or maybe not?!?!

But thanks for your reply!!!!!

[john1290]

pacoreguenga,

He is using a DV passthrough (i.e analog to DV digital converter) which means that he has no choice but to capture at 720x480 because this is a set resolution for DV. With the exceptions of a few camcorders, DV is interlaced. Can't you just de-interlace it when converting to mpeg-2? Or is that even necessary? I am assuming that the analog to digital conversion feature of the camcorder automatically inter-laces the video when converting it to DV. Any thoughts on this?

Thanks

YG

Even though the DV camera is the pass through, I think I can tell my capture program to capture at a lower rez......I think......haven't really tried.

[yg1968]

Perhaps I am missing something but if you are using the analog to digital conversion feature of your camcorder, you have no choice but to capture at 720x480 as this resolution is implied in the DV format. If you change these capture settings, you are encoding on the fly while capturing the DV (which is not ideal). You are better off merely importing the DV stream into an avi file and encoding as a second step.

I am not sure if you are better off de-interlacing upon converting to mpeg-2 if your source is VHS. I have gotten good results de-interlacing. But I haven't compared it to leaving it interlaced.

[john1290]

Perhaps I am missing something but if you are using the analog to digital conversion feature of your camcorder, you have no choice but to capture at 720x480 as this resolution is implied in the DV format. If you change these capture settings, you are encoding on the fly while capturing the DV (which is not ideal). You are better off merely importing the DV stream into an avi file and encoding as a second step.

I am not sure if you are better off de-interlacing upon converting to mpeg-2 if your source is VHS. I have gotten good results de-interlacing. But I haven't compared it to leaving it interlaced.

I see what you're saying......hmmmmm.....guess I'll just leave well enough alone and keep going as am. I just wanted to toss my question out there and see if I could be doing something better.

[House de Kris]

[quote="pacoreguenga"]
Now let's talk about tapes.
VHS and 8mm can be captured at 352 x 240 as they aren't interlaced signals. This can be seen on rollers. (credits at the end of a movie) If you look close enough, you will notice black and color lines aternating.
SuperVHS and Hi8 share higher resolutions, as they are interlaced. This gives you effectively two fields for frame. They aren't really 720 x 480, but you can capture at that resolution, as they are close enough to it.
[quote]

Where does this tripe come from? VHS and 8mm are interlaced and record both fields.

[yg1968]

The de-interlacing option is more complicated than I thought. See the following links:

http://www.puremotion.com/videoediting/reference/technical/interlacedvideoexplained/

http://www.puremotion.com/videoediting/reference/technical/whatisdeinterlacing/index.htm

This article adresses the advantages of capturing at higher resolution:

http://www.lukesvideo.com/highvslow.html

[pacoreguenga]

John1920:

Just keep on capturing at 720 x 480.

House de Kris:

You are right. My apologies for my inaccuracy. They record both fields, but at half resolution. I'm terribly sorry, but I haven't used VHS for production since school.

[ktnwin]

[/quote]

Even though the DV camera is the pass through, I think I can tell my capture program to capture at a lower rez......I think......haven't really tried.[/quote]


No, you cannot change the capture resolution of DV. The camera sends out a DV stream at 720x480 res and the capture program simply stores that on disk, capture program does not touch the DV stream at all. This is how DV camcorder works.

Later another conversion software like TMPGEnc will allow changing the resolution, bit rate, etc..

If you use an analog capture card then that''s a different story, most of them allow users to set capture size.