Doom9's Forum - View Single Post

BaronVlad · 29th August 2002, 22:25

20.) When capturing I always get dropframes

- When TV and sound device are not working at the same clock speed or the computer is not fast enough, VirtualDub will drop frames during the capturing session. The captured movie will not contain such frames. Ideally you will get no such frames. But let's for a second assume that you do. In PAL we have 25 frames per second. If 75 frames (corresponds to 3 seconds of video) have been dropped during a 3h recording session you will not be able to notice the difference visually but with audio you will notice that the movie will get asynch. Therefore in VirtualDub you should always activate the adjust video clock option (in Virtual Dub:
Capture -> timing -> activate Adjust video clock) which ensures that video and audio stay in synch.
If you like to know more about dropframes:
English Language (rather funny)
or the original in German Language

In other programs there are other options to avoid drops or to get audio and video in sync afterwards.

21.) What can I do against dropframes?

- First lets clear some misconceptions that many users have. Dropped frames are not a disease that needs to be cured. It is simply a solution to maintain A/V sync by dropping or doubling a frame. The problems start when you have dropframes which are not caused by A/V sync algorithm. If you have so many dropped frames that you will notice them (the video "stutters") then the problem is NOT your capture software (if you use a good one) but in your system (software and/or hardware) and/or source (e.g. bad VHS tape). It is normal that Huffyuv clips stutter as this codec was not meant to be used for playback, so you should compress it before watching and if the picture "stutters" then you have a real problem.

You can also (example: VirtualDub), disable the "adjust video clock" and try to synchronize the audio after capturing (could be a bit complicated, but possible).
This way you won't get any dropped frames from the A/V synch algorithm.

To test if you get dropped frames that are not caused by the A/V sync you can disable audio capturing. If you still get dropframes you know your problem lies elsewhere (software and/or hardware) and/or source (e.g. bad VHS tape).

We recommend the use of the excellent VirtualDub modification VirtualDub_sync by Andreas Dittrich ( http://www-user.rhrk.uni-kl.de/~dittrich/sync/ ). It uses a different approach to maintain the A/V sync, a real time audio resampling routine and it drops only frames if the resample routine would add audible errors.

Most users getting many dropframes have simply not optimized their system. We suggest that those people go the recommandations below, and also take a look at Question 4 (recommended hardware).

- Be sure that the DMA (direct memory access) mode is activated on your HDs
- defrag your system and capture disk (you can also quick format your capture disk if you have nothing to loose on it)
- Turn any active background proces off (virus scanners, indexing services, etc.)
- To turn off these background programs you can easily use Enditall
- 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 during a capture.
- always restart before you capture (if you use Win9x)
- lower your capture resolution or framerate (changing the framerate should be the last resort, always keep the framerate same as the source, e.g. 25 for PAL)
- use a separate HD for your captures (on a different controller than your system disk), be sure your HD is fast enough (you can use, for instance, VD's benchmark)
- Try to change your codec setting and/or try a different capture codec (e.g. MJPEG based instead of Huffyuv)
- Change the screen resolution to 800x600, 256 colors and 85Hz refresh rate
- activate cropping (only useful for 16:9 video where you can crop the black bars)
- if you use VirtualDub (or one of its modifications) make a test capture (F7) before the real capture
- make a fixed swap file or disable it
- try a different capture software (you could first try the freeware programs and then switch to the shareware programs

)
-if you have a Brooktree/Conexant based card you can try to crop a few pixels of the vertical resolution (PAL example: 704x574 or 704x572

-use a TBC (http://www.questronix.com.au/html/info_tbc.htm)

If everything fails (still too many frame drops) try capturing without sound. If you have NO framedrops for a long time, then your soundcard is using a sampling frequency other than the desired one (instead of, for example, 44100). Possible solutions to this problem (as experienced by Ookami) are:

- use VirtualDub Sync (if not yet)
- try changing the sampling frequency
- fiddle with the settings in MULTIMEDIA - AUDIO - Recording adv. properties (Sample rate conv. and hardware acceleration)
- buy a better souncard

22.) I did everything by the book but it simply doesn't work!

Here are some advanced hints. Use them with care!
- Get the latest driver for your capture device or try an alternative
one (like BtWinCap).
- Get the latest drivers for your mainboard.
- Remove every PCI card except your capture device and GFX card.
- If it works with only these two insert your soundcard.
- Use the video input of your GFX card instead of the one of your capture device
- Try another operating system.
- Deactivate unused HD controller(s).
- Change the screen resolution to 800x600, 256 colors and 85Hz refresh rate.
- Use the latest DMA drivers for your mainboard.
- Switch PCI/AGP Latency to 32 in your BIOS.
- Use regular 33 pin cables for your UDMA disks.
- Turn off ACPI mode in the BIOS.
- Reinstall your operating system and use the latest drivers.
- Monitor the CPU temperature while you capture. Your CPU may get too hot.

23.) Do I have to be at home when I'm capturing?

- No! If you use a modified version of VirtualDub you can use your PC as a VCR. For a how read the following Capture Guide.
The modified VirtualDub version can be found here.

24.) The guide is nice but do I really have to configure everything all on my own?

- Yes, but if you have done it once, it can be saved. And there are many guides available that will help you.

25.) How do I calculate the bitrate for the encoding session after capturing?

- If you didn't sleep during calculus classes you should have no problem figuring that one out. But just in case you can use a bitrate calculator like that one comes along with GKnot.

26.) Where is the official VirtualDub website?

- The official VirtualDub site is http://www.virtualdub.org/, NOT http://www.virtualdub.net/.
The latter is a German VirtualDub 'mod' site.

27.) Where can I find VirtualDub filters?

http://www.virtualdub.org/ The official site
http://neuron2.net/ Donald Graft's (neuron2) site
http://vdfilters.videoxone.de/index_e.html fISH's VD filter site

28.) How do I convert my VHS tapes to DVD?

http://forum.doom9.org/showthread.php?s=&threadid=19558
http://forum.doom9.org/showthread.php?s=&threadid=17616

29.) I could need a glossary, could you please write one?

No need for that. This link should help you: http://www.quantel.com/domisphere/infopool.nsf/html/DFB

30.) There are more and more VirtualDub modifications, is there a list somewhere?

Sure. Here

. Altough not all of these are really useful for capturing only.

VirtualDubMod as a summary of modifications: http://virtualdubmod.sourceforge.net/

Andreas Dittrich's sync modification : http://www-user.rhrk.uni-kl.de/~dittrich/sync/
Joe Redfish's modification (1.4.9.2 VCR + A. Dittrich's sync modification) : http://www.virtualdub.net/ VirtualDubMpg2 (AC3, VBR MP3 and MPEG2 supported) : http://virtualdubmpg2.chez.tiscali.fr/
The Cyrius modification (OGM supported) : http://cyrius.bunkus.org/
Belgabor's VirtualDubAVS http://www.geocities.com/belgabor/vdubavs
For Nando's Nandub go to Doom9's download page

31.) What is DVB and where can I find more infos?

Look at these links:

http://forum.doom9.org/showthread.php?s=&threadid=34625 ('What is the best DVB card?')

and the forum section: http://forum.doom9.org/forumdisplay.php?s=&forumid=64

32.) What can I do against the various interferences in the picture?

Please have a look at this: http://forum.doom9.org/showthread.php?s=&threadid=46079

That's all folks! Please use this forum for feedback.

One last word:
Capturing video is a mix between finding the right settings and being lucky. Nobody will be able to tell you the best possible setup for your system. If it doesn't work just keep on trying the various things mentioned in this FAQ. And don't forget to share all the nice tricks you find out on your journey with the rest of the world.

P.S.: this FAQ is by no means complete. There's no word about the peculiarities of individual capture device or about the use of filters. Thanks to Hawk, der_Karl, fISH, Kika, Ted66 and all the other guys from Ultimateboard and Doom9.org, all the tips from the folks at DVDboard.de

29th August 2002, 22:25	#2 \| Link
BaronVlad Jetzt nochmal auf Deutsch Join Date: Oct 2001 Location: Berlin, Germany Posts: 411	20.) When capturing I always get dropframes - When TV and sound device are not working at the same clock speed or the computer is not fast enough, VirtualDub will drop frames during the capturing session. The captured movie will not contain such frames. Ideally you will get no such frames. But let's for a second assume that you do. In PAL we have 25 frames per second. If 75 frames (corresponds to 3 seconds of video) have been dropped during a 3h recording session you will not be able to notice the difference visually but with audio you will notice that the movie will get asynch. Therefore in VirtualDub you should always activate the adjust video clock option (in Virtual Dub: Capture -> timing -> activate Adjust video clock) which ensures that video and audio stay in synch. If you like to know more about dropframes: English Language (rather funny) or the original in German Language In other programs there are other options to avoid drops or to get audio and video in sync afterwards. 21.) What can I do against dropframes? - First lets clear some misconceptions that many users have. Dropped frames are not a disease that needs to be cured. It is simply a solution to maintain A/V sync by dropping or doubling a frame. The problems start when you have dropframes which are not caused by A/V sync algorithm. If you have so many dropped frames that you will notice them (the video "stutters") then the problem is NOT your capture software (if you use a good one) but in your system (software and/or hardware) and/or source (e.g. bad VHS tape). It is normal that Huffyuv clips stutter as this codec was not meant to be used for playback, so you should compress it before watching and if the picture "stutters" then you have a real problem. You can also (example: VirtualDub), disable the "adjust video clock" and try to synchronize the audio after capturing (could be a bit complicated, but possible). This way you won't get any dropped frames from the A/V synch algorithm. To test if you get dropped frames that are not caused by the A/V sync you can disable audio capturing. If you still get dropframes you know your problem lies elsewhere (software and/or hardware) and/or source (e.g. bad VHS tape). We recommend the use of the excellent VirtualDub modification VirtualDub_sync by Andreas Dittrich ( http://www-user.rhrk.uni-kl.de/~dittrich/sync/ ). It uses a different approach to maintain the A/V sync, a real time audio resampling routine and it drops only frames if the resample routine would add audible errors. Most users getting many dropframes have simply not optimized their system. We suggest that those people go the recommandations below, and also take a look at Question 4 (recommended hardware). - Be sure that the DMA (direct memory access) mode is activated on your HDs - defrag your system and capture disk (you can also quick format your capture disk if you have nothing to loose on it) - Turn any active background proces off (virus scanners, indexing services, etc.) - To turn off these background programs you can easily use Enditall - 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 during a capture. - always restart before you capture (if you use Win9x) - lower your capture resolution or framerate (changing the framerate should be the last resort, always keep the framerate same as the source, e.g. 25 for PAL) - use a separate HD for your captures (on a different controller than your system disk), be sure your HD is fast enough (you can use, for instance, VD's benchmark) - Try to change your codec setting and/or try a different capture codec (e.g. MJPEG based instead of Huffyuv) - Change the screen resolution to 800x600, 256 colors and 85Hz refresh rate - activate cropping (only useful for 16:9 video where you can crop the black bars) - if you use VirtualDub (or one of its modifications) make a test capture (F7) before the real capture - make a fixed swap file or disable it - try a different capture software (you could first try the freeware programs and then switch to the shareware programs ) -if you have a Brooktree/Conexant based card you can try to crop a few pixels of the vertical resolution (PAL example: 704x574 or 704x572 -use a TBC (http://www.questronix.com.au/html/info_tbc.htm) If everything fails (still too many frame drops) try capturing without sound. If you have NO framedrops for a long time, then your soundcard is using a sampling frequency other than the desired one (instead of, for example, 44100). Possible solutions to this problem (as experienced by Ookami) are: - use VirtualDub Sync (if not yet) - try changing the sampling frequency - fiddle with the settings in MULTIMEDIA - AUDIO - Recording adv. properties (Sample rate conv. and hardware acceleration) - buy a better souncard 22.) I did everything by the book but it simply doesn't work! Here are some advanced hints. Use them with care! - Get the latest driver for your capture device or try an alternative one (like BtWinCap). - Get the latest drivers for your mainboard. - Remove every PCI card except your capture device and GFX card. - If it works with only these two insert your soundcard. - Use the video input of your GFX card instead of the one of your capture device - Try another operating system. - Deactivate unused HD controller(s). - Change the screen resolution to 800x600, 256 colors and 85Hz refresh rate. - Use the latest DMA drivers for your mainboard. - Switch PCI/AGP Latency to 32 in your BIOS. - Use regular 33 pin cables for your UDMA disks. - Turn off ACPI mode in the BIOS. - Reinstall your operating system and use the latest drivers. - Monitor the CPU temperature while you capture. Your CPU may get too hot. 23.) Do I have to be at home when I'm capturing? - No! If you use a modified version of VirtualDub you can use your PC as a VCR. For a how read the following Capture Guide. The modified VirtualDub version can be found here. 24.) The guide is nice but do I really have to configure everything all on my own? - Yes, but if you have done it once, it can be saved. And there are many guides available that will help you. 25.) How do I calculate the bitrate for the encoding session after capturing? - If you didn't sleep during calculus classes you should have no problem figuring that one out. But just in case you can use a bitrate calculator like that one comes along with GKnot. 26.) Where is the official VirtualDub website? - The official VirtualDub site is http://www.virtualdub.org/, NOT http://www.virtualdub.net/. The latter is a German VirtualDub 'mod' site. 27.) Where can I find VirtualDub filters? http://www.virtualdub.org/ The official site http://neuron2.net/ Donald Graft's (neuron2) site http://vdfilters.videoxone.de/index_e.html fISH's VD filter site 28.) How do I convert my VHS tapes to DVD? http://forum.doom9.org/showthread.php?s=&threadid=19558 http://forum.doom9.org/showthread.php?s=&threadid=17616 29.) I could need a glossary, could you please write one? No need for that. This link should help you: http://www.quantel.com/domisphere/infopool.nsf/html/DFB 30.) There are more and more VirtualDub modifications, is there a list somewhere? Sure. Here . Altough not all of these are really useful for capturing only. VirtualDubMod as a summary of modifications: http://virtualdubmod.sourceforge.net/ Andreas Dittrich's sync modification : http://www-user.rhrk.uni-kl.de/~dittrich/sync/ Joe Redfish's modification (1.4.9.2 VCR + A. Dittrich's sync modification) : http://www.virtualdub.net/ VirtualDubMpg2 (AC3, VBR MP3 and MPEG2 supported) : http://virtualdubmpg2.chez.tiscali.fr/ The Cyrius modification (OGM supported) : http://cyrius.bunkus.org/ Belgabor's VirtualDubAVS http://www.geocities.com/belgabor/vdubavs For Nando's Nandub go to Doom9's download page 31.) What is DVB and where can I find more infos? Look at these links: http://forum.doom9.org/showthread.php?s=&threadid=34625 ('What is the best DVB card?') and the forum section: http://forum.doom9.org/forumdisplay.php?s=&forumid=64 32.) What can I do against the various interferences in the picture? Please have a look at this: http://forum.doom9.org/showthread.php?s=&threadid=46079 That's all folks! Please use this forum for feedback. One last word: Capturing video is a mix between finding the right settings and being lucky. Nobody will be able to tell you the best possible setup for your system. If it doesn't work just keep on trying the various things mentioned in this FAQ. And don't forget to share all the nice tricks you find out on your journey with the rest of the world. P.S.: this FAQ is by no means complete. There's no word about the peculiarities of individual capture device or about the use of filters. Thanks to Hawk, der_Karl, fISH, Kika, Ted66 and all the other guys from Ultimateboard and Doom9.org, all the tips from the folks at DVDboard.de __________________ Hochachtungsvoll BaronVlad Deutsch >> Capture FAQ - Capture Guide Englisch >> Capture FAQ - Capture Guide Last edited by jggimi; 10th September 2003 at 20:49.