World Cup HD with Lumagen HDQ

[Bryce Curdy]

Had my Lumagen HDQ installed earlier this afternoon. Have connected to Pioneer 504 using HDMI and RGB Scart (for SD channels). Watching Germany - Costa Rica on BBC HD. Utterly stupendous!

Brief initial impressions suggest that SD looks better via RGB Scart at 576i than HDMI at 1080i. Regardless of input selected, the improvement on the SD channels is probably more than on HD. Pioneer DVD868 (via HDMI) also superb. Also have a HDMI connected Sony DVD/HDD recorder, PS2 and Xbox (original) connected. Will keep you updated on my impressions, but it will take me a while to get my jaw off the floor!

[madshi]

Originally Posted by Bryce Curdy

Pioneer DVD868 (via HDMI) also superb.

Make sure you select 576i YCbCr output in the Pioneer (if possible).

[welwynnick]

Originally Posted by madshi

Make sure you select 576i YCbCr output in the Pioneer (if possible).

Madshi, do you think YCbCr looks significantly better than RGB over HDMI?

Nick

[madshi]

Originally Posted by welwynnick

Madshi, do you think YCbCr looks significantly better than RGB over HDMI?

I think it depends very much. The source is encoded in YCbCr. The displays all show RGB. So someone somewhere in the video chain has to convert YCbCr to RGB. The big question is: Who does that the best way? If you tell the DVD player to do the conversion, there will be some (quite little, but still some) loss, because HDMI supports only 8 bits in RGB, as a result there will be some minor rounding losses. I'd guess that the Lumagen is better in color space conversion, cause that's one of the things it was designed for. But even if it's "only" as good as the Pioneer, you get a benefit by transporting YCbCr to the VP, because then there are no rounding losses. The Lumagen then takes 8bit YCbCr, does its calculations (deinterlacing + scaling) and finally converts things to RGB. Honestly, I'm not sure whether the Lumagen is doing the conversion to RGB first and then doing deinterlacing/scaling, or vice versa. But you'll have benefits either way, as the Lumagen with the newest firmware does all calculations in 10bit internally. Only the end result is then dithered down to 8bit RGB.

If the Lumagen deinterlacing/scaling algorithms only work on YCbCr data, then sending it RGB is double bad, because then the DVD player would do YCbCr->RGB, the Lumagen would do RGB->YCbCr, then do deinterlacing/scaling etc, then do YCbCr->RGB again. But I'm not sure how the Lumagen does things internally. I do know that the Mosquito is internally doing its calculations in YCbCr, though.

In any case sending YCbCr to the Lumagen can't be worse than sending it RGB (unless the Lumagen screws things up majorly, which I'm sure it does not). Sending it YCbCr is most probably better. Maybe the difference is minor, but why settle for a suboptimal connection?

[welwynnick]

Thanks Madshi, I'm quite familiar with all the theory, and more, but I was wondering if you had any specific experience with using both RGB and YCbCr from a DVDP. I too, expect YCbCr to be better, but I figured it might be a small difference, and a 10 bit YCbCr output may be a more worthwhille improvement over 8 bit.

I would still expect 8 bit YCbCr over HDMI to have LSB errors. Golden-eyed AVers always say that 8 bit YCbCr over SDI is still better than 8 bit YCbCr over HDMI , so I have to assume that there is still some internal DVD processing going on with the latter (after the MPEG decoder). I think the 868 does YCbCr 4:4:4 rather than 4:2:2, so that may explain some of it - there's a chroma upscaling process being performed in the DVD rather than the scaler.

With regard to which format is used internally by scalers, I have been wondering that for a while. Realta processors promote their abilty to process 30 bit 4:4:4 video, so you might deduce that older processors do not, and may be limited to component. That sounds reasonable, as it would make for more efficient use of processing resources. But I'm starting to speculate now, and it would be interesting to hear from someone like Dale about how it is normally done. In the meantime I assume using YCbCr over HDMI will be better wherever it's available.

Nick

[Bryce Curdy]

ITV via the Freeview in my Sony HXD910 HDD/DVD recorder looked very good and clearly better than ITV via Sky.

[acave]

I have my Humax HD box via lumagen on passthrough. The lumagen adds stutters and slowdown. Its fine for other stuff but I don't see no real benefit for a scaler in the chain with HD video based material.

[Gordon @ Convergent AV]

acave: I'd be grateful if you can email me your cfg file and the version of firmware you are running and to what display. Your findings do not seem to be representative of the majority of Lumagen HD users.

Gordon