How to record AVI files using VirtualDub Sync
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How to record AVI files using VirtualDub Sync |
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VirtuaDub Sync is an excellent tool for recording with a TV card. This free VirtualDub clone can be downloaded from http://www-user.rhrk.uni-kl.de/~dittrich/sync/. First you have to install VirtualDub (http://www.virtualdub.org/). Stick to Version 1.5.10 or earlier. Then follow the directions for copying The VD Sync module to your VD folder.
VirtualDub Sync's creators say:
"When capturing video with your TV-card and audio with your soundcard simultaneously, after some time audio becomes desyncronized with video. This is because the clock of the soundcard is not syncronized or locked to the framerate of the incoming TV-Signal. Thus the number of audio-samples per frame will change slowly in time. Ok, when adding some timestamps while recording, or using some data framing techniques and e.g. bit stuffing mechanisms, this is no problem anymore, when using these information for playback.
For short sequence capturing, that does not matter because this effect becomes visible only when recording some longer periods (depends on the quality of the soundcard-oscillator and on the oscillator(s) in the tv-broadcast-station or in your VCR).
In order to syncronize audio and video, all capture programs we know (Virtualdub, AVI_IO, etc.) throw away or duplicate frames when audio is behind or in front of video.
Solution:
In order to synchronize audio and video we apply a realtime sample rate conversion to the audio signal and do not throw frames away, anymore. That is, we have some means to permanently measure the time delay between audio and video during the capturing process and e.g. if there are too much audio samples per frame we reduce the number of audio samples in such a way, that there is no audible degradation (in the professional music domain, sample rate conversion is applied when mixing digital audio of different sources, but in a hardware-circuit like the AD1896 from Analog Devices). In order to avoid additional jitter, the measured time delay is feed into a servo loop with a high time constant.
So even when capturing many hours, the number of samples is as specified (e.g. PAL with 25frames per second and 44.1kHz audio sampling frequency, there have to be exactly 44100/25 = 1764 samples per frame)."
In our experience, the clone works. Even the worst tapes will be recorded in sync with dropped frames duplicated and extra frames thrown away, so that time code fits perfectly all the way.
However, no two computers are alike, so all we can give you is our own VD Sync settings. If they don't work, try modifying them:
In VD Sync, select file/capture avi to open capture screen.
Then:
| • | Audio/compression: PCM, 24000 kHz; 16 bit; Mono; 46 KB/sec |
| • | Video/overlay: ON |
| • | Video/Format: 320x240; YUY2 |
| • | Video/compression: Microsoft MPEG-4 Video Codec 2; Keyframe every 1 seconds; Compression Control 100; Data rate 6000 (for better picture quality - but bulkier files - use the Morgan or Picvideo MJPEG V2 codec) |
| • | Capture/Settings: Capture Audio ON; Drop % limit 10; Max Index entries 324000; Video buffer limit 150; Audio buffer limit 10; Audio buffer size 36000; Lock Video Stream to audio ON, frame rate: 25.000 (that's for PAL. For NTSC: 29.9700). |
| • | Capture/Preferences: Default capture driver: Microsoft WDM Image Capture (Win32) - or whatever you have installed |
| • | Capture/Timing: Resample audio data dynamically to match video clock |
Save your settings with Capture/all four save options ON
Set recording length with Capture/Stop conditions
Select recording path with F2
Start recording with F6
Tip: Do NOT use other programs while recording. If frames are being dropped, close your internet access and disable as many running processes as possible. One of our computers dropped 44 frames a minute, until we disabled the Virus Monitor (Kaspersky). Then it ran for an hour without dropping one single frame.