A question regarding recording from TV and resolutions

vbimport

#1

Resolution refers to the number of lines that can be displayed on a standard television. Theoretically the more lines of resolution that can be displayed, the better the picture quality. The NTSC broadcast television standard is 525 lines, of which 330 lines are displayed on a standard television. VHS videotapes offer approximately 240 lines, super VHS tapes offer up to 400 lines, and DVDs offer approximately 500 lines of resolution. http://hdtv.digitalinsurrection.com/hdtvglossary.php

Also, the max. resolution supported by most Mpeg authoring packages is 720 X 576 which is the max. resolution of DVD Video

  1. Seems to me that recording standard TV at DVD quality settings is simply a waste of disk space?? The dvd recording cannot be any better than the input quality?

Likewise, it seems to me to get the “best” home recorded dvd one should use a high definition source and downcovert it NOT to standard tv quality (which is what all the programs seem to advertise including the recent update to Windows Media 5) but rather downconvert to the highest dvd resolution??

  1. What am I missing??

Thanks///bobbo.


#2

If you are talking about a cable broadcast yes, but check out newer TVs, they can display higher resolution than the regular standard 240line resolution TV.

  1. Seems to me that recording standard TV at DVD quality settings is simply a waste of disk space?? The dvd recording cannot be any better than the input quality?

BTW, for NTSC, DVD uses 720x480 - and yes, capturing at a higher resolution than your source will NOT give a better picture - in some cases and depending on the quality of the video chipset, it can have the opposite effect.

You are indeed wasting bandwidth - I thikn such resolutions are best suited for capturing from S-VHS/Hi-8/Digital 8/Mini DV high resolution high quality sources - Even digital cable does not use that high of a resolution. Which is why computer software allows you to change resolution down to Half-D1, part of the DVD specifications, with HALF horizontal resolution (352x480) this is fairly enough for VHS sources and with the resolution cut in half, your bitrate efficiency is doubled… So your capturing at 352x480 @ 4mbit would be as efficient as an 8mbit. On a standalone DVD recorder you have no choice. Capturing in XP & SP mode will give you 720x480 resolution, capturing at LP/MP/EP will capture in half-D1 (352x480) and in some recorders, an SLP mode @ 352x240 :slight_smile: Given the chipsets used in most consumer recorders I would personally stick to XP & SP whenver you can and whenever disc space is not an issue.

Why don’t you try out for yourself - Capture from a live TV feed, in 720x480 and one in 352x480 (assuming you are using software which let’s you change this). On a PC software you will in some cases notice a better picture at half-d1 for such sources given the bandwidth efficiency - On some DVD recorders you might see things differently - results will vary from one unit to another.


#3

Hey Greg===thanks. I understand everything you posted but you throw me at the end. If you agree that you are wasting bandwidth if you record at higher resolution than the source, then why do you recommend doing it “whenever disk space is not an issue?” Isn’t disk space always an issue especially if the picture quality doesn’t improve??

When I first got my fast computer I bought 4-5 capture cards and compared them all at all settings with my standalone liteons. Uniformily, all looked great at the 720x480 setting, but who wants 1-2 hour dvds that only match standard broadcast tv signal??

What I found was that at the lowest bit rate and 352X240 settings, ALL of the computer solutions were inferior to the standalones!!!. Im my opinion, this lowest bitrate setting pretty much matched the standard tv pictures. Still frame captures do show a quality difference but this difference is unnoticeable to me in day to day viewing.

STILL–I’d like to make some quality recording now for later viewing on High Def tvs. And to do that, my original question stands==ie, recording a high def signal that has been downconverted to standard ntsc makes NO SENSE to me and yet that is what all the vendors are advertising???

I’m looking for a capture card that will sample the high def signal directly to the 720x480 format. I think some solutions <might> do this but the advertising copy just doesn’t give that information. Thanks again Greg==I think we are pretty close. ///bobbo.


#4

Ok I will explain myself - In my case disc space is not an issue. Why ? Because I usually record one program at a time on DVD. The DVDs I produce for myself and the companies I deal with are 2 hours or less and my own VHS transfers are usually SP 2 hours. The fact I use a PC with a professional hardware encoder, I get excellent quality at low bit rates compared to consumer encoders, so why would I use lower resolution anyway ? I am not in need of the space or the extra quality since I will get none. Now, where it is efficient to use Half-D1 is, say you are recording material over 2 hours or you want to fit multiple programs on a disc, this is where you need to squeeze as much material in the space given, so you will use half resolution and a lower bitrate, but which will be doubled in efficiency. Example, you have try to fit a 3 hours VHS onto 1 DVD, you would use Half-D1 resolution (352x480) @ 3.5 mbit/s (example)… given you have half the data to process and half the data being used by the given bitrate, your 3.5 will be just as good as a 7mbit. In case of stand alone DVD recorders you have no choice, anything lower than SP is recorded in Half-D1 automatically, you cannot change that (that’s how it works on most consumer dvd recorders and even professional ones). On the PC however, I have the choice to change capture resolution at ANY given bitrate. If you are using a DVD Recorder then the resolution is taken care for you.

I hope it is not too confusing.

What I found was that at the lowest bit rate and 352X240 settings, ALL of the computer solutions were inferior to the standalones!!!. Im my opinion, this lowest bitrate setting pretty much matched the standard tv pictures. Still frame captures do show a quality difference but this difference is unnoticeable to me in day to day viewing.

Don’t use still frames as reference - Your brain cancels most of this out during motion anyways.

I would NEVER recommend recording at 352x240, that is the lowest resolution used and if I am not mistaken, it uses MPEG-1 (which is also part of the DVD specs) (only at that resolution). I would not go below 352x480 for VHS. Cable broadcast uses a higher resolution than a typical VHS which is 240lines, so you might want to try and experiment and see whcih is suitable for you.

STILL–I’d like to make some quality recording now for later viewing on High Def tvs. And to do that, my original question stands==ie, recording a high def signal that has been downconverted to standard ntsc makes NO SENSE to me and yet that is what all the vendors are advertising???

I’m looking for a capture card that will sample the high def signal directly to the 720x480 format. I think some solutions <might> do this but the advertising copy just doesn’t give that information. Thanks again Greg==I think we are pretty close. ///bobbo.

I am not sure I am understanding you here. The current DVD specifications uses standard definition content only. So for now if you have capturing from a hi-def source you have no choice but to use 720x480. By hi-def source you are talking about high definition right ? I hope you are not confusing with S-VHS,DV, etc…

There are some DVD players that will upconvert a standard definition DVD to allow a better picture on your future (or current) high definition capable TV. It is NOT a replacment for true hi-def but on quality players and sets it can get quite decent results.

You might get away at using low bit rates on your regular TVs, but try viewing those on future large screen TVs and they will look ugly, which is why ultimately you want to use the highest bitrate whenever possible, since on a 3 hour VHS (for example) it is not possible, then using half resolution will allow double the efficiency of the low bit rate you will use. That is the point I was trying to make, but I hope this is not too confusing.


#5

IMO, the real source is the big factor.
Even digitally via dvb-s you can terrible results and content anyway.

Nowadays we kinda have dvb-s2 and dvb-c2, which is hdtv/mpeg4/H.264/AVC with up to 1080p, in normal cases 1080i or 720p.


#6

Thanks Greg==I hope that wasn’t too much effort. I thought we connected on your first answer, but I have lost you on the second one. To be fair, I get similarly lost every time I post this question. “Everyone” recommends recording at the highest bit rates and resolutions even when a few like yourself admit the recording cannot be better than the source. You are about the first that has agreed that comparing still shots is not a good measure==I think if we were in the same room, I could learn alot from you.

As you recommend, I guess I’ll wait till I get that big screen High Def TV and then go back and re-evaluate all the resolutions and bit rates and see what lowest setting I can use before I see a difference. Thanks Again ///bobbo. and Chef==>Huh? (smile!)


#7

Another DVb-S2 card from statup. In looking at DVB-S2 PCI cards, I came across this company http://www.digitalcruz.com

They claim they have the DVB-S2 card in several Beta sites and he said that the card will be available in late July for general purchase.

The datasheet is found at http://www.digitalcruz.com/datasheets/dgc1000s.pdf

The marketing person I talked to is James Chang. He also told me that they will consider pre-orders of the card. He said that the card will be included in a media center PC made by a Japanese manufacturer. I told him to check out mytheatre and told him there is a large community of users utilizing Mytheatre that is waiting for DVB-S2 cards with TFEC and 8PSK.

All in all, he seemed quite open and willing to offer information(probably because they are a startup). I asked him how to preorder and he said to send him an e-mail and he will put me on a list. He said they haven’t planned for a larger beta, but due to multiple requests, they are considering offering a small run for an expanded BETA in a couple of weeks and have the card orderable via their online store. He did say that if they offer the expanded BETA it will be a limited amount available (he said less than 50) because they want to ensure the card drivers are solid before general release and they cannot support a large BETA program yet.

Finally, I asked him about the DUAL ATSC card because I am looking for a card like that due to my small case and he said that is going to be available in August.

I was going to order the technotrend card, but now with this delay, I am thinking of ordering the Digital Cruz card and give it a try. I also like that they are coming out with the Dual ATSC card using a PCI-e x1 slot.


#8

The TT card will be available to the public within the next 10 days, I’ve heard rumours… PCI version and external usb2 thing.


#9

Anyone bought this card from DigitalCruz yet?

Now that we have double-tuner cards for DVB-S (like from Pinnacle) I expect that this also comes for DVB-S2…later.


#10

Well, I’m having fun!! Downloaded a few sample High Definition film clips (1080P and 720p with .wmv extensions) and then used winavi to re-encode them at 480p. These dvd quality final products are much better than the dvd quality images produced at the same settings using Standard Television Signal from Comcast===> SO, the quality of the source is very controlling and anyone recording standard TV at 720x480 is certainly wasting space. I don’t notice much when it comes to video quality but I can tell the difference here! (smile)

FYI, its frustrating that the lastest version of winavi is 7.1 and it fails to re-encode the sample highdef material without any explanation whereas winavi version 3.5 and Nero have no problems at all with the same files.

I’m noticing that my final burned/re-encoded file is only one third the size of the original .wmv file. Am I correct in thinking my downloaded high definition samples were already compressed and not the same file type I will get if I do direct recording of OTA signals? I wish I could go out and just buy all the different equipment and check this all out, but $800 for a Sony DVR and another $1000 for the TV is a bit much for me until I “know” I can put it all to “good use.” Thanks for any input. ///bobbo.


#11

Actually Blue-Ray titles use mpeg2 instead of mpeg4 on most of their releases…
Gives some idea.


#12

Chef–I’m stretching to get your reference, but I think you mean Blue-Ray is less compressed than mpeg4? In context, that “should” mean that .wmv files use mpeg4 and that is why my re-encoding effort is returning somewhat minimal results?

Now, I doubt OTA Broadcasters are using Blu-Ray disks as their source material, so I wonder what relevance their compression strategies are?

Anyway, --YES–next step is to find out if .wmv files are always compressed. I did assume they normally have “some compression” but that they are user determined? Kinda raises the issue of what the Broadcasters are using? Uncompressed mpeg2 is what I see in print the most but as time goes on I do assume the source material will become more variable to include blue-ray, wmv, and realtime as well?

Anyway, I’m convinced ((but not yet proven-out)) that using high definition as my source, I’m going to wind up with excellent images on my self made DvD’s all at a very reasonable price for storage. High Def transmissions?===>YES!! High Def home recordings?===>NO!! /// bobbo.