Kiến Thức Chung

Capturing with VirtualDub [Settings Guide]

5: Capture (top menu)

Capture Video F5,F6
I use F6 to to start capture. Some say you can use F5, but many advise against it (known as audio “compatibility mode” and said to result in gradual loss of audio sync. I don’t click this menu item to start capture, I just press F6. Vdub Help has more info about using compatibility mode..

Test Video capture
I used this a time or two and saw the info panel light up with all kinds of capture statistics, but I never knew if it actually makes a capture file. Anyone who knows more is welcome to chime in.

Stop Capture Esc
I press the “Esc” key to stop capture.

Real time profiler
Some people have used this, but I never have. Comments welcome.

Settings…

Set the frame rate for capture here if it isn’t already set. The default is 15.0000. I never use “Wait for OK”.

Preferences:

Set the items you want displayed in the capture window’s right-hand information panel by clicking on the item. I use the defaults, which includes more than you often need.

You can change the app’s hot keys if you want. Good luck remembering what you did.

5B Stop conditions…

I’ve set no limits here. When a limit is reached, capture stops. It’s OK if you want to go shopping or to your 9-to-5 job while running a capture, but you’ll never know what actually happened unless you watch the video. If your tape stopped running, the capture continues for the set limit.

In this menu, Accept uses the settings for the current session. Save keeps the settings until you change them yourself.

Timing…

The timing options seem to cause the most hassle and confusion for people, especially since the effects can vary with many devices. Manufracturers don’t make cards specifically for

These options set up the way VirtualDub matches video to audio during a capture. Video frames can stream in from the video capture with irregular timestamps due to timing inaccuracies and interference with system background tasks. Bad timing can also come from the source video or the player. During capture these issues have to be resolved for something more consistent and correct.

These settings tell VirtualDub to make corrections. What you really should be doing is avoiding off-sync timing in the first place with a frame TBC. VirtualDub will do the best it can, but it won’t be as predictable as a proper TBC.

General options
– – – – – – – – – – –


If enabled, VirtualDub rejects frames timed too close together in the frame timing scenario for the chosen frame rate. As one writer noted, 3 frames with timestamps that are 10ms apart (a 100 fps timing rate) cannot fit into a 29.97 fps stream. Some or all of these frames will be dropped.

This option is enabled by default.

If this option is turned off, all captured frames are retained as-is. If audio resampling is also turned off at the same time (see below), disabling this option can result in lost audio/video sync.


In the capture information panel, null frames (usually dupes of previous or following frames) display as the number of “inserted frames”. When captured frames are timed too far apart for the intended frame rate, VirtualDub inserts dummy frames — e.g., two captured frames timed too far apart would have a dummy (dupe) frame inserted between them. I’ve seen sample videos with 2 or up to 6 inserted frames.

Avoid this in the first place with a proper TBC. Again, if the audio resampling is also turned off at the same time, the result would be loss of a/v sync.

This option is enabled by default.

*** Note in the attached image for my AIW 9600XT and AIW 7500 settings that I’ve disabled both options. I’ve auditioned high quality TBC’s, and even with these in circuit I would get one or two dropped or inserted frames, sometimes up to 3 or 4 over an hour. The problem seems to be that no one knows what VirtualDub considers to be the limit for “good” timing. Even a quality TBC can output minor errors that don’t fit VDub’s timing formula, whatever it is. Now and then I turn them back on, then off. I work with VHS restoration in very small segments and in great detail. For
years I’ve looked for dropped/inserted frame and haven’t found any with these options disabled and a good player and TBC in use.

Without a TBC, turning on these options can result in a flood of dropped and inserted frames plus bad audio sync. Without a TBC, turning them off might result in fewer dropped frames (maybe) or maybe none reported, but you’ll lose audio sycn even with the audio sync options turned on.

Moral: Options or no options, use an external frame TBC or external pass-thru DVD with decent frame timing sync. I often use a Panasonic ES10 or ES15 for pass-thru (but they don’t remove Macrovision the way my AVT-8710 does and are less than perfect with really crummy tapes).

– – Null frame burst limit
The default is 10. Sets the max number of consecutive dummy frames that VirtualDub will insert. Leave this as-is. If you get 10 consecutive dummy frames, you have problems beyond serious.

Resync mode
– – – – – – – – –

This mode disables auto-resync. VirtualDub won’t monitor the a/v input for a/v timing errors, therefore sync quality depends on the timing accuracy of your input. Moral: connect your TBC.

Exceptions I’ve noted are USB and other capture devices with their own internal audio input and timing correction, which can often play havoc with VirtualDub’s idea of what proper sync values are. A Hauppauge USB user reports having to deselect this option even with a frame TBC in circuit.

Tells VirtualDub to speed up or slow down the video clock to match the audio clock. This can often result in dropped/inserted frames, which is why I don’t use it. The effect depends on whether your video or audio clock is the worst offender. If the audio clock is cleaner than the video clock, you could get dropped/inserted frames. If the opposite is true, you could get fewer drops and inserts. Since neither clock is always precisely accurate anyway, the choice is up to you.

With cards having integrated audio clock correction, see below. If there are any ongoing audio clock adjustment, it’s reported in the info panel.

This is the resync option I’ve elected to activate. With a good player and TBC, both a/v clocks are in decent shape but minor variations in the video clock that do occur aren’t discernible in my setup, even with music. If your a/v stream is totally wacky you could get some odd sounding, sour or warbly audio with this option turned on.

If turned on, audio timing is stretched or compressed to match video, with no effect on video timing. NOTE: This mode is recommended only for audio capture to uncompressed PCM. You can still use this mode for compressed audio codecs, but why use compressed audio for lossless capture?

This mode is selected by default.

Tells VirtualDub to correct video timing to compensate for slight timing errors. Some users report that this option is used with the “sync audio to video” resync turned on or when you’re not capturing audio.

To make things more complicated: if resync mode is set to “sync video to audio”, the video timing correction in that video-to-audio resync mode will be disabled. This “Correct video timing” option is also supposed to be automatically disabled if integrated A/V capture timing within the capture device (such as many USB devices) is detected. That is, it’s supposed to be disabled with integrated devices such as the ATI 600 USB, but users report that it isn’t. So if you’re using a capture device with integral audio/video timing inside, click on the “disable resync” menu item below, and turn this one off.


This item is disabled by default.

Capture devices with integrated audio and video usually use internal audio-video clocks to correct or avoid sync errors between the two streams. When using those devices but not enabling this option, loss of audio sync is common. When this option is turned on, Virtualdub is supposed to automatically disable the “auto-resync” option above when such a device is detected. But apparently VDub doesn’t always detect those objects properly, so turn this item on when using
those devices. You could also experiment with turning on or off “”.

I have always had “Automatic” enabled and set for the default 30 blocks. See VirtualDub online Help.

I’ve not enabled any of these. It’s often asked, how do you define whether or not the source timestamps and clock are accurate? If they aren’t, do you want them in your video? I believe the default is the “force audio clock” entry.

Disk I/O…

My settings for this item, shown above, are the defaults. Not sure how this item applies in the overall scheme of things. Some say it’s allied to capture to lossy codecs which encode rather just losslessly fast-compress. More info is welcome here. One user reports setting a larger chunk size and more chunks to speed up display in Preview mode, but I won’t meddle with these settings unless I know what they’re doing.

Spill system setup
Spill files are not being used here.

Full screen
Optional. I get a slowdown and weird aspect ratio using it.

Hide display on capture
This one’s up to you.

Display large timer
This option displays a humongous minutes/seconds incrementing numeric timer at the bottom of the window. Time spent capturing is already displayed in the info panel, so who needs this? The time characters are shown here actual size:

Show information panel
I leave this turned on. You can turn it off if you want. On by default.

Show status bar
Turned on by default. Much the same thing is in the info panel

Timing graph
– – – – 5F1 Timing graph TBC on R.png
– – – – 5F3 Timing jitter – no tbc 2 R.png
Displays a continuously updated graphics info bar along the bottom border. What the line colors mean is indicated in the small legend of colors at the left of the display. Normally you’d use this for test and analysis. Ideally the lines shown should be straight and consistent, though small variations are common. The timing graph below was made with the AIW 7500 AGP using a line and frame pass-thru ES10 for TBC during capture:

The timing graph below was made without a line or frame TBC during capture. If you get wild lines like those shown below you’re in trouble, and VirtualDub capture is working hard to make what corrections it can:

Anyone who has used this display graph extensively is welcome to offer more details.

Log
Text display of capture activity for the current session. Right-click the window to save as a file, or capture to clipboard, or exit.

Enable multisegment capture
Not used in these examples.

Start capture on left-click in pane
I leave this disabled. Click at the wrong time, and you’ve screwed up.

Auto increment filename after capture
I leave this disabled and set my own capture file names.

Enable timing log
I’ve never used this. I already have enough to worry with.

My capture settings, Continued from previous posts:I use F6 to to start capture. Some say you can use F5, but many advise against it (known as audio “compatibility mode” and said to result in gradual loss of audio sync. I don’t click this menu item to start capture, I just press F6. Vdub Help has more info about using compatibility mode..I used this a time or two and saw the info panel light up with all kinds of capture statistics, but I never knew if it actually makes a capture file. Anyone who knows more is welcome to chime in. VirtualDub Help has more details.I press the “Esc” key to stop capture.Some people have used this, but I never have. Comments welcome.Set the frame rate for capture here if it isn’t already set. The default is 15.0000. I never use “Wait for OK”.Set the items you want displayed in the capture window’s right-hand information panel by clicking on the item. I use the defaults, which includes more than you often need.You can change the app’s hot keys if you want. Good luck remembering what you did.I’ve set no limits here. When a limit is reached, capture stops. It’s OK if you want to go shopping or to your 9-to-5 job while running a capture, but you’ll never know what actually happened unless you watch the video. If your tape stopped running, the capture continues for the set limit.In this menu,uses the settings for the current session.keeps the settings until you change them yourself.The timing options seem to cause the most hassle and confusion for people, especially since the effects can vary with many devices. Manufracturers don’t make cards specifically for VirtualDub ‘s options. VirtualDub Help has more details on many of these items.These options set up the way VirtualDub matches video to audio during a capture. Video frames can stream in from the video capture with irregular timestamps due to timing inaccuracies and interference with system background tasks. Bad timing can also come from the source video or the player. During capture these issues have to be resolved for something more consistent and correct.These settings tell VirtualDub to make corrections. What you really should be doing is avoiding off-sync timing in the first place with a frame TBC. VirtualDub will do the best it can, but it won’t be as predictable as a proper TBC.If enabled, VirtualDub rejects frames timed too close together in the frame timing scenario for the chosen frame rate. As one writer noted, 3 frames with timestamps that are 10ms apart (a 100 fps timing rate) cannot fit into a 29.97 fps stream. Some or all of these frames will be dropped.This option is enabled by default.If this option is turned off, all captured frames are retained as-is. If audio resampling is also turned off at the same time (see below), disabling this option can result in lost audio/video sync.In the capture information panel, null frames (usually dupes of previous or following frames) display as the number of “inserted frames”. When captured frames are timed too far apart for the intended frame rate, VirtualDub inserts dummy frames — e.g., two captured frames timed too far apart would have a dummy (dupe) frame inserted between them. I’ve seen sample videos with 2 or up to 6 inserted frames.Avoid this in the first place with a proper TBC. Again, if the audio resampling is also turned off at the same time, the result would be loss of a/v sync.This option is enabled by default.Note in the attached image for my AIW 9600XT and AIW 7500 settings that I’ve disabled both options. I’ve auditioned high quality TBC’s, and even with these in circuit I would get one or two dropped or inserted frames, sometimes up to 3 or 4 over an hour. The problem seems to be that no one knows what VirtualDub considers to be the limit for “good” timing. Even a quality TBC can output minor errors that don’t fit VDub’s timing formula, whatever it is. Now and then I turn them back on, then off. I work with VHS restoration in very small segments and in great detail. Foryears I’ve looked for dropped/inserted frame and haven’t found any with these options disabled and a good player and TBC in use.Without a TBC, turning on these options can result in a flood of dropped and inserted frames plus bad audio sync. Without a TBC, turning them off might result in fewer dropped frames (maybe) or maybe none reported, but you’ll lose audio sycn even with the audio sync options turned on.Moral: Options or no options, use an external frame TBC or external pass-thru DVD with decent frame timing sync. I often use a Panasonic ES10 or ES15 for pass-thru (but they don’t remove Macrovision the way my AVT-8710 does and are less than perfect with really crummy tapes).The default is 10. Sets the max number of consecutive dummy frames that VirtualDub will insert. Leave this as-is. If you get 10 consecutive dummy frames, you have problems beyond serious.This mode disables auto-resync. VirtualDub won’t monitor the a/v input for a/v timing errors, therefore sync quality depends on the timing accuracy of your input. Moral: connect your TBC.Exceptions I’ve noted are USB and other capture devices with their own internal audio input and timing correction, which can often play havoc with VirtualDub’s idea of what proper sync values are. A Hauppauge USB user reports having to deselect this option even with a frame TBC in circuit.Tells VirtualDub to speed up or slow down the video clock to match the audio clock. This can often result in dropped/inserted frames, which is why I don’t use it. The effect depends on whether your video or audio clock is the worst offender. If the audio clock is cleaner than the video clock, you could get dropped/inserted frames. If the opposite is true, you could get fewer drops and inserts. Since neither clock is always precisely accurate anyway, the choice is up to you.With cards having integrated audio clock correction, see below. If there are any ongoing audio clock adjustment, it’s reported in the info panel.This is the resync option I’ve elected to activate. With a good player and TBC, both a/v clocks are in decent shape but minor variations in the video clock that do occur aren’t discernible in my setup, even with music. If your a/v stream is totally wacky you could get some odd sounding, sour or warbly audio with this option turned on.If turned on, audio timing is stretched or compressed to match video, with no effect on video timing. NOTE: This mode is recommended only for audio capture to uncompressed PCM. You can still use this mode for compressed audio codecs, but why use compressed audio for lossless capture?This mode is selected by default.Tells VirtualDub to correct video timing to compensate for slight timing errors. Some users report that this option is used with the “sync audio to video” resync turned on or when you’re not capturing audio.To make things more complicated: if resync mode is set to “sync video to audio”, the video timing correction in that video-to-audio resync mode will be disabled. This “Correct video timing” option is also supposed to be automatically disabled if integrated A/V capture timing within the capture device (such as many USB devices) is detected. That is, it’sto be disabled with integrated devices such as the ATI 600 USB, but users report that it isn’t. So if you’re using a capture device with integral audio/video timing inside, click on the “disable resync” menu item below, and turn this one off.This item is disabled by default.Capture devices with integrated audio and video usually use internal audio-video clocks to correct or avoid sync errors between the two streams. When using those devices but not enabling this option, loss of audio sync is common. When this option is turned on, Virtualdub is supposed to automatically disable the “auto-resync” option above when such a device is detected. But apparently VDub doesn’t always detect those objects properly, so turn this item on when usingthose devices. You could also experiment with turning on or off “”.I have always had “Automatic” enabled and set for the default 30 blocks. See VirtualDub online Help.I’ve not enabled any of these. It’s often asked, how do you define whether or not the source timestamps and clock are accurate? If they aren’t, do you want them in your video? I believe the default is the “force audio clock” entry.My settings for this item, shown above, are the defaults. Not sure how this item applies in the overall scheme of things. Some say it’s allied to capture to lossy codecs which encode rather just losslessly fast-compress. More info is welcome here. One user reports setting a larger chunk size and more chunks to speed up display in Preview mode, but I won’t meddle with these settings unless I know what they’re doing.Spill files are not being used here.Optional. I get a slowdown and weird aspect ratio using it.This one’s up to you.This option displays a humongous minutes/seconds incrementing numeric timer at the bottom of the window. Time spent capturing is already displayed in the info panel, so who needs this? The time characters are shown here actual size:I leave this turned on. You can turn it off if you want. On by default.Turned on by default. Much the same thing is in the info panel- – – – 5F1 Timing graph TBC on R.png- – – – 5F3 Timing jitter – no tbc 2 R.pngDisplays a continuously updated graphics info bar along the bottom border. What the line colors mean is indicated in the small legend of colors at the left of the display. Normally you’d use this for test and analysis. Ideally the lines shown should be straight and consistent, though small variations are common. The timing graph below was made with the AIW 7500 AGP using a line and frame pass-thru ES10 for TBC during capture:The timing graph below was made without a line or frame TBC during capture. If you get wild lines like those shown below you’re in trouble, and VirtualDub capture is working hard to make what corrections it can:Anyone who has used this display graph extensively is welcome to offer more details.Text display of capture activity for the current session. Right-click the window to save as a file, or capture to clipboard, or exit.Not used in these examples.I leave this disabled. Click at the wrong time, and you’ve screwed up.I leave this disabled and set my own capture file names.I’ve never used this. I already have enough to worry with.

Attached Images

5A Capture Settings.png (8.6 KB, 5097 downloads)

5B Stop conditions.png (10.0 KB, 5075 downloads)

5C Capture timing options.png (21.8 KB, 5159 downloads)

5D Disk I-0.png (9.9 KB, 5084 downloads)

5E Large Timer.png (4.0 KB, 5043 downloads)

5F1 Timing graph TBC on R.png (8.8 KB, 5042 downloads)

Last edited by sanlyn; 08-12-2016 at

10:32 AM

.

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