Capture FAQ. Revised 10 June 2006

[BaronVlad]

Capture FAQ

Last update: added DScaler USB comments to Q3.

Please read this FAQ before asking in the forum. Many problems can be solved this way and you will help all the nice people here. Thank you.

Please note that some parts are a translation of a German FAQ, therefore many links go to German pages, the German capture Guide is translated and now hosted here. A discussion about the guide is going on in the forum. Feel free to join us, if you have a suggestion.


And now

1.) What is capturing?

· An analogue input source (TV, (S)VHS, Camcorder, etc.) is digitized and stored on a computer.


2.) What do I need to capture?

· All you need is a video input on your PC. You can either use the video input of your TV- Capture device or the video input of your Graphics card (e.g. ASUS Deluxe or ATI All in Wonder serie). Using the video input of your GFX card will result in a better signal.


3.) Which TV Capture cards are commonly used?

· The most common video Capture Chip's are produced by Brooktree, and/or Conexant. (Conexant bought Brooktree). The most frequently used chip variants are the BT848 and 878. There are also cards which use chips by. Zoran (ZR36125), or Philips (SAA7146). Some devices even have an FM-Tuner for wireless reception (BT848 or 878). For the BT8x8 chips you can find alternative drivers (which most likely surpass the original ones) on Sourceforge:
sourceforge.net.

BTW:
Good programs for watching TV on your computer are Dscaler. or MoreTV.
MoreTV apparently works only with BT8x8 chipsets.
DScaler originally worked only with the BT8x8; now it interoperates with USB outboard equipment. See DScaler capture via USB for details.

A few threads that might help you selecting a TV card:
Someone Suggest a Good TV Tuner Card

Card recommandation


4.) Which hardware is recommended?

- Here is a great article on Scuba's site:

http://www.highvid.com/hardware_tips...rd_sel_1.shtml


5.) Which OS is recommended?

- It depends. As a rule of thumb, use Win98 SE if you own a older system and/or a older capture card or GPU, Windows 2000/XP in all other cases. As with most things, you cannot know it until you try it.

6.) What capture programs exist?

Freeware:

VirtualDub: http://www.virtualdub.org/
VirtualDubMod: http://virtualdubmod.sourceforge.net
VirtualDub Sync VCR: http://www.virtualdub.net/
VirtualVCR: http://virtualvcr.sourceforge.net
Scheduler für VirtualVCR: http://www.zisoft.de/video

Shareware:

AVI_IO
iuVCR
ReelCap


7.) What is the best capture program?

- Most of the users here use VirtualDub. Take a look at these threads:

http://forum.doom9.org/showthread.php?s=&threadid=17440
http://forum.doom9.org/showthread.php?s=&threadid=17251
http://forum.doom9.org/showthread.php?s=&threadid=17373

8.) How do I use VirtualDub?

- There are differents guides on how to use it, just have a look:

http://www.virtualdub.org/virtualdub_docs
http://www.virtualdub.org/virtualdub_kb

and

http://forum.doom9.org/showthread.php?s=&threadid=16662


9.) At which resolution should I capture?

· First let's have have a detailed look at the input. There are two different systems which are commonly used (PAL and NTSC). PAL (Phase Alternate LINE) is used in most European countries (France and some Eastern Europe countries use SECAM which is closely related to PAL). On the PC the TV picture can be displayed in various resolutions, up to the native PAL resolution (768x576). The maximum resolution you can use to capture depends on your capture card and most cards support 7**x576 where the horizontal resolution only depends on your capture device. In order to keep the proper aspect ratio of the picture you can capture either at full resolution (768x576) or at 1/4 resolution (384x288). If you intend to put the video on a VCD use 352x288 pixels, for SVCDs use 480x576 (both times the picture will be horizontally squeezed a bit and then unstretched during playback).
· Using 1/4 resolution has a distinctive advantage. The output will not have any interlacing effects making deinterlacing unnecessary. For more information about interlacing please refer to (De)interlacing - Basics (German link)and this http://www.doom9.org/ivtc-tut.htm. On the other hand using this resolution you will sacrify quality as you're not storing all the information of the original signal.
· No matter what resolution you chose make sure that you use one of the abovementioned horizontal resolutions.

For further informations on the subject refer to the following threads:

http://forum.doom9.org/showthread.php?s=&threadid=21067
http://forum.doom9.org/showthread.php?s=&threadid=18143
http://forum.doom9.org/showthread.php?s=&threadid=16013
http://forum.doom9.org/showthread.php?s=&threadid=43198

Deinterlace/Resolution:
http://forum.doom9.org/showthread.php?s=&threadid=40940

A great guide about finding the right resolution is "Der Karl's Capture Karten aspect ratio fuer Dummies ;-) " PDF (sorry only in German language): http://forum.doom9.org/showthread.php?s=&threadid=32604


10.) Why is a high resolution recommended when capturing VHS.?

- We all know that VHS VCR has a resolution of 320x240?
A: First, VHS has no "resolution" of 320x240. This is just an old rumor. Second, if you use filters, there is a big difference in using a low resolution (less informations for the filter) and full PAL (or NTSC) resolution. Last but not least it all depends on your taste, if you are satisfied with a 352x288 direct Divx ;-) capture, then by all means use such a low resolution. In the end only you can tell if the quality is satisfactory.

A very good thread that explains in theory why all those '320x240 stories' are just incorrect http://forum.doom9.org/showthread.php?s=&threadid=34122 .


11.) What settings could/should I use?

- Please read the threads below to get different user's opinions:

http://forum.doom9.org/showthread.php?s=&threadid=23633
http://forum.doom9.org/showthread.php?s=&threadid=19595
http://forum.doom9.org/showthread.php?s=&threadid=18925
http://forum.doom9.org/showthread.php?s=&threadid=17310
http://forum.doom9.org/showthread.php?s=&threadid=16013


12.) Why does my capture software propose a resolution of 640x480?

· It may be that the drivers for your card or the capturing software was written for the NTSC market. If your country uses PAL use one of the resolution suggested above.


13.) OK ! Now how do I capture ?

.. Available English Guides:
- doom9.org Capture Guide of BaronVlad, translated by killingspree with the help of Donald Graft: http://www.doom9.org/capture/start.html
- Luke's (Cart's) capture guide: http://www.lukesvideo.com/
- CK's guide (sadly down): http://go.to/videocapture/
· there are also some good German capture guides available (hopefully
they will be translated one day):
the Capture Guide of BaronVlad.
· Very good alternatives:
- Mattheo's (low&high) quality Capture Guide
- Hawk's Capture Guide
- http://captureworld.videoxone.de/
or here:
- Hawk's Capture Guide v.1.2
- Hawk's Capture Guide v.3.0 (SneakPreview)

A few additional thoughts:
All the guides mentioned above tell you how to capture into a lossless compression first and compressing into Divx (or another compression codec) afterwards.If you absolutely want to capture directly to DivX/XviD instead of an uncompressed format:
- It is possible if:
1. The maximum resolution is set to 384x288,
2. You set the codec to 1-Pass mode and
3. GMC and Bi-directional Encoding have been switched off.


14.) But why?

BECAUSE! ... The encoding process is lossy and your source material will be changed making the later use of filters useless (especially VHS often has artifacts that you would like to eliminate prior to encoding to your target format. Plus, capturing is a very demanding process for your PC. If your PC has to encode to DivX at the same time it may no longer be able to keep up with all the data and your DivX file will have dropped frames Thus, we recommend the lossless Huffyuv codec. If your HD is not large enough you can still use an MJPEG codec (e.g.: PicVideo Q 19/20) which is more suited for capturing.

Depending on your TV chips there are some additional details to
keep in mind:

- If you have a BT8x8 chip, the OVERLAY mode has to be switched off during the capturing session.
- When using a Philips based card, the OVERLAY mode has to be activated!!
- Capturing on WIN2K/XP using WDM drivers does not necessarily have to work. If you use VirtualDub you should install one of the following software if you get an error message like Error 418: NO capture DEVICES installed:
- vfwupd.exe
- dx80bda.exe
- wdm-vfw-wrapper

But there is no guarantee that it will work. And there's a catch:
Using the wrapper the processor load is higher which could result in more dropped frames.


15.) But I still want to capture in DivX!
Do as you please. But think about the following first:

- Have you ever managed to hit a desired file size (e.g. 700MB) in 1-Pass mode?
- You can only cut a DivX at a keyframe. What will you do about the advertising in the middle of a film if it doesn't start with a keyframe?
- Filters (including cropping) cannot be used during capturing so you will have to re-encode the movie if you plan to perform any operations on the input picture. You'll end up encoding the movie twice and since the source for your 2nd encoding session will already be compressed the quality will be much lower than if you were to use Huffyuv and in the end you didn't save any time at all.


16.) Can I crop the input?

- Yes you can. Use the null transform filter to crop. However, you will hardly know in advance how many pixels you have to crop. Imagine watching the news in full screen 4:3 format and the movie you're going to capture is widescreen. You will only know how many pixels to crop once the movie has started. In order to save CPU power you can crop conservatively (about 20 pixels from top and bottom) which will save some CPU time so you'll get less dropped frames.


17.) I want to capture using Huffyuv at full resolution, but my files get huge. What can I do about it?

- Use an MJPEG codec like PicVideo and set the codec to quality class 19 (for really long movies use class 18 ). The files you'll get will be much smaller but the encoding is still almost lossless.

18.) Do I have to register PicVideo?

- Contrary to Huffyuv, PicVideo is not freeware, but you should think about supporting them since they help you solve your size problems. However, if you don't want to spend any money you can simply cut off the logo after capturing (cropping).

19.) Capturing stops after roughly half an hour. What's wrong?

- Win98/ME (ME is very buggy!) use the FAT32 filesystem, meaning that files cannot be larger than 4 GB and AVI files are limited to 2 GB. Windows will remind you with a friendly error message that you have reached this limit. However, Avery Lee, has a simple and ingenious solution. It is called "Multi segment Capture". There's a Guide explaining how to use this feature that you usually don't even get in commercial programs.