DVD2AVI - YUV -> RGB Question

[ABC123]

When frameserving using DVD2AVI, should I be selecting PC Scale or TV scale under the YUV -> RGB option? I've made a few DVDs to SVCDs but never realized about this option until a couple of days ago.

[adam]

Ok, in case you are the type of person who just wants to be told what to do...

If you use CCE (Cinema Craft Encoder) to encode than ignore the pc/tv scale setting altogether, and just make sure output is set to YUV. In CCE set the luminance level to 0-255.

If you use TMPGenc than you have two options, either one will pretty much give you the same result. 1) Set dvd2avi to RGB output and set it to pc scale, encode in TMPGenc with default settings. 2) Set dvd2avi to RGB output and set it to tv scale and enable the "Output YUV data as Basic YCbCr not CCIR601" which is located on the Setting/Quantize Matrix tab.

As far as other encoders are concerned, I'd have to test them to see what colorspace they encode in by default, but my guess would be that you generally you would want to use pc scale in dvd2avi.

In case you are the type of person who wants to know why they are selecting one option over another...

Tv's use a color space of 16-235, which corresponds to tv scale in dvd2avi, and pc's use a colorspace of 0-255, which corresponds to pc scale in dvd2avi.

Since a DVD is obviously meant to be played on a tv, it is encoded in the 16-235 colorspace, and it also happens to be YUV. Now you want to preserve this 16-235 color space throughout your frameserving/encoding process. You'd think that this means you want to encode at 16-235, but this is incorrect. Setting the encoder to 16-235 actually compresses the luma, regardless of what it actually is, while setting it to 0-255 stretches the scale out, effectively preserving the luminance level exactly as it is.

So, CCE is the only software encoder I know of that can accept YUV input. So its best to not convert to RGB in dvd2avi. This preserves quality and saves a heck of alot of time. It will also keep your movie in the 16-235 color space. So now in the encoder, you want to use a luminance level of 0-255 to prevent any further luma compression.

When using TMPGenc you have no choice but to convert to RGB. By default, TMPGenc encodes in the 16-235 scale (actually TMPGenc lists it as 8-235) so you would want to use pc scale in dvd2avi to first stretch your luma scale out to 0-255, and then let TMPGenc compress it back to spec. And by reversing the colorspace TMPGenc encodes in, by changing that option on the Quantize Matrix tab, you basically just want do the opposite. Use tv scale to keep the source 16-235, and then TMPGenc will use 0-255 to keep from further compressing the luma scale.

So now what does this colorspace even mean? It refers to your luminance levels, basically the dynamic range of your colors. A camera has a slightly wider dynamic range than what a tv can, or is meant to display. So once something is filmed it has colors which, as far as your tv is concerned, are whiter than white, and blacker than black. They are illegal colors, and if you play them on your tv they just get clipped which looks really bad. That is why 16-235 colorspace is used, it compresses these colors so that they are no longer in the off spec ranges.

So, like I said, your DVD is the starting point and has already had these off spec colors compressed to spec. If you were to set your luminance level incorrectly, than you would further compress your luminance level and crop out some of the legal black, and legal white levels. Basically, your whites won't be a white as they can be and your blacks won't be as black as they can be, and actually the entire picture can appear either too bright or too dark depending on the nature of your source.

I think too many people overlook this very important setting and actually, I think there is alot of incorrect information floating around out there. Generally, the TMPGenc guides I see are accurate in telling you to use pc scale in dvd2avi, but all of the CCE guides I see are incorrect in telling you to use 16-235 in the CCE video tab. This will compress your colors too much and you won't get the full dynamic range of colors that your source has. Alot of times when you do this blacks look almost gray and it also makes your entire movie less compressible.

[ABC123]

Wow! Thanks. Wasn't expecting that much info.

[scottb721]

Adam, I have been using TV Scale in DVD2AVI for my TMPGEnc encodes for my SVCDs.
What changes can I expect to the end reuslt if I switch to PC Scale ? Blacker blacks and whiter whites?

I understand the idea of keeping as much info in the intermediate source files before the final compression is done so your advice prevents premature compression of the colour range, correct ?

thanks

[adam]

Adam, I have been using TV Scale in DVD2AVI for my TMPGEnc encodes for my SVCDs.
What changes can I expect to the end reuslt if I switch to PC Scale ? Blacker blacks and whiter whites?

Basically yes. Depending on the movie it may or may not even be noticable, but since it requires no extra work you might as well do it correctly.

I understand the idea of keeping as much info in the intermediate source files before the final compression is done so your advice prevents premature compression of the colour range, correct ?

No not premature compression, it prevents unnecessary compression. The only reason the colors must be compressed at all is because a camera captures colors outside of what a tv supports. When the DVD was encoded they already took care of these colors, compressing them back into spec. You want to prevent any further compression at all, because the source is already exactly how you want it.

[scottb721]

Where has all this knowledge stemed from Adam you Legend!