Friday, 1 June 2012

My XVid Configuration For TV Capture Using VirtualDub

Depicted below are the XVid parameter settings that I use for my TV captures with VirtualDub. The XVid parameters have been tuned so that I can capture directly into XVid with reasonable video quality. Capture resolution is set at 720x576 - i.e. a high resolution capture. The frame rate is set at 25 fps. Audio is captured and compressed into MP3 at 96 kbps. I do use the sharpen and dynamic noise reduction filters during capture, but not both at the same time as I do not have enough CPU processing power (see Extending V2CRS - Enabling VirtualDub Filters). CPU usage level is about 90% - 110% on average.

I am using KWorld PCI Analog TV Card Lite (PVR-TV 7134SE) as my capture device. I have 1GB RAM and an Intel Pentium Dual-Core E5400 2.7GHz processor installed on my ASUS P5G41C-M LX motherboard. I do not get any drop frames. But a sudden burst of multiple inserted frames do happen, but very rarely. It all depends on the scene that is being captured and whether VirtualDub could cope.

I do at times get scenes that are distorted, lasting for about a second or 2. I am not sure but I believe this is due to my not too optimal settings for Motion Search Precision and VHQ mode. ( Update 17-Dec 2012: There is actually a problem with my media player during playbacks; no problems if I were to view my captures on my PC with Media Player Classic).


Banding artifacts do creep in at times. Setting the Quantization Type to MPEG will make the Banding artifacts even more prominent. So, I have decided to use H.263 as my Quantization Type.
I get the best capture quality when I set the value of Max I-frame quantizer at 4 and Max P-frame quantizer at 4. I have experimented setting the value of Max I-frame at 4 and Max P-frame at 5 but I find the video quality to be unsatisfactory as not enough detail is being captured. In a scene with a fish swimming in murky water, clarity was lost and the fish just got blended into the background.

Setting the value of Max B-frame quantizer has no effect on the captured B-frame quantizer value. Instead, captured B-frame quantizer values are determined by the fields in B-VOPs (see the first dialog box above) and its neighbouring I-frame and P-frame. I use more B-frames to increase compression and thus reducing the size of my captures. In addition, as I wanted a high quantizer value for my B-frames (again for more compression) I decided to increase the value of B-VOPs Quantizer Offset to 3.
I have to set the value of Motion Search Precision to 4-High and VHQ Mode to 0-Off. Increasing either one or both options will increase CPU usage beyond the capacity that VirtualDub could cope. This causes intermitten burst of multiple inserted frames to occur.

Below are the rest of the XVid settings.







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