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| Hawker7 |
| Posted: Mar 8 2004, 04:39 AM |
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Unregistered
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Hi all,
I am working on 8mm anolog played by a Digital 8 vtr. I have been trying both Vdub and Avisynth to frame serve to TMPGEnc and I am wondering which codec to use? One that outputs RGB or YUV. I have downloaded Canopus and Mainconcept for YUV and Panosonic and Sony for RGB colorspace.
I used Avisynth script, Info() and it confirms the codecs output the proper colorspace but which colorspace should I be using? I am concerned about conversion of the colorspace and it seems that RGB should be used with Vdub and YUV for most of the filtering on Avisynth.
What do you guys reccomend. Is it anything to be to concerned about. Since I will be frameserving to TMPGEnc I understand it will convert to RGB output anyway.
Your Codec confused newbie
Hawker  |
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| phaeron |
| Posted: Mar 8 2004, 05:01 AM |
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Virtualdub Developer
Group: Administrator
Posts: 7773
Member No.: 61
Joined: 30-July 02
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The color space for DV is always YCbCr (YUV), but exactly which format depends on the standard in use. NTSC DV uses 4:1:1 (1/4 horizontal color res.), whereas PAL DV uses 4:2:0 (1/2 both). The most straightforward target format is thus YUY2/UYVY (4:2:2, 1/2 horizontal). This is the default, preferred format for the original Avisynth. The newer versions of Avisynth prefer YV12 (4:2:0), but I wouldn't recommend that if you are using NTSC DV as you will lose vertical color resolution.
As both MPEG and DV are YCbCr, you will get better performance if you avoid roundtripping through the RGB format. There is also a tiny amount of error introduced in such conversions but I doubt you will notice it for a single round trip. Conversion between different YCbCr formats, on the other hand, is fairly cheap.
One problem to watch for is whether your chroma is being interpolated properly. The Microsoft DV codec interpolates chroma, but some early codecs didn't and the result was color blockiness. For the 4:1:1 NTSC format, this can be rather apparent. Last time I checked Avisynth didn't interpolate chroma vertically when upsampling YV12 to YUY2, but it's been a while and that may have been fixed.
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| Hawker7 |
| Posted: Mar 9 2004, 05:10 AM |
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Phaeron,
Could you elaborate on roundtriping. Do you mean opening in Vdub, then full processing back to RGB without compression?
It seems to me if I am using the Panasonic DV codec which decompresses to RGB colorspace and then frame serving with VD to TMPGEnc that I am avoiding any roundtripping. Correct?
Is this the way you would try to conserve the most color information or would you use another method or codec?
Thanks for all your help on the forum
Hawker  |
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| phaeron |
| Posted: Mar 9 2004, 05:33 AM |
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Virtualdub Developer
Group: Administrator
Posts: 7773
Member No.: 61
Joined: 30-July 02
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The DV format is stored as YCbCr regardless of what codec you are using; this is also true of MPEG. All codecs that decompress DV to RGB really do so by decompressing the YCbCr data first and then converting that. Thus, frameserving in RGB means your video data is being converted to RGB and back to YCbCr.
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