color gradients look bad on my tv - recoding makes it worse

[Psythorn]

I stumbled across an issue with my LCD TV (Philips 37PF9731). Color gradients are not soft. It seems that there is no dithering - looks a bit like 8Bit instead of 16Bit.

This effect is best seen with the DreamWorks intro. The soft blue color gradients of the clouds etc.

Also this seems to be an issue of my TV it cleary gets worse with recoded material. I'm using nero recode right now with AVC (h264), 2 pass, quality set to extreme and giving around 1.5GB to 2GB for a movie.

Input quality is similar to not recoded dvd material [720 x 4??]- so I do think that bitrate is no way to low.

Somebody got an idea what happens here and if there is a way to improve it ?

[Dark Shikari]

That's because all modern video formats do use 8-bit; 8-bit luma (brightness).

Dithering is extremely difficult to encode into the video stream--that's why some people consider film grain so important (it covers up banding).

[Psythorn]

I tried to dig a bit further and noticed this. If using my Laptop in "Clone" Mode to see the image on the LT Display and on my TV I can see that the TV is definetly doing worse in displaieng the color gradients... much less banding...

Dithering is a nightmare to compress so I do understand why it is filtered away... But the dithering I'm missing is the dithering the tv should use to blend color gradients more smootly...

That's because all modern video formats do use 8-bit; 8-bit luma (brightness).
This could be a hint why recoding does make it worse. If mpeg2 is not a "modern format" under this point of view and if mpeg2 did a better job with color gradients compared to divx or h264 this could explain why recoding does make it worse...

[Dark Shikari]

I tried to dig a bit further and noticed this. If using my Laptop in "Clone" Mode to see the image on the LT Display and on my TV I can see that the TV is definetly doing worse in displaieng the color gradients... much less banding...

Dithering is a nightmare to compress so I do understand why it is filtered away... But the dithering I'm missing is the dithering the tv should use to blend color gradients more smootly...


This could be a hint why recoding does make it worse. If mpeg2 is not a "modern format" under this point of view and if mpeg2 did a better job with color gradients compared to divx or h264 this could explain why recoding does make it worse...Nope, MPEG-2 uses 8-bit luma also. The reason it does better with gradients is because MPEG quantization (available in Xvid/DivX as opposed to H.263 quantization) is much better at retaining fine details, while H.263 tends to smooth the resulting video. This smoothing eliminates the grain/dither that was on the image to begin with. Of course, you need lots of bits to keep the grain/dither effectively either way.

[Psythorn]

Nope, MPEG-2 uses 8-bit luma also. The reason it does better with gradients is because MPEG quantization (available in Xvid/DivX as opposed to H.263 quantization) is much better at retaining fine details, while H.263 tends to smooth the resulting video. This smoothing eliminates the grain/dither that was on the image to begin with. Of course, you need lots of bits to keep the grain/dither effectively either way.

Ok... does this mean I might get better results if i'd use DIVX/XVID and giving more bitrate ? How many GB would you suggest would be needed to see this happen when using "normal" DVD quality material as input ?

[Dark Shikari]

Ok... does this mean I might get better results if i'd use DIVX/XVID and giving more bitrate ? How many GB would you suggest would be needed to see this happen when using "normal" DVD quality material as input ?Xvid on CQ2 shouldn't have too much of an issue with banding.

If you want to stay with AVC, try x264--my adaptive quantization (a few threads down, I think) may be able to solve your problem.

[CruNcher]

Also some Laptop/Notebook GFX solutions use special power saving display modes with reduced colors if unpluged i saw this with my ATI Xpress 200 based Notebook.
Windows said it's still useing 16 million colors but it didn't as banding became even more obvious in this mode. It's a Powerplay feature look @ such stuff closely. But i don't think LCD TVs make use of such stuff, they don't really need to save Power that extreme ;)

[HowlerX]

I'm assuming you are using a PC connected to an LCD HDTV (presumably via its PC RGB input). One thing I've noticed is that if you use a media player that uses the overlay mixer to display video the banding really stands out. I'm not sure if this applies to every video card though. I connected a PC with a Nvidia 6600GT graphics card and the banding when using overlay mixer was annoying. I tried VMR9 (or Haali's Renderer) and it was a much, much better looking image. I tried a laptop with Intel graphics and the overlay mixer with that card wasn't as bad as Nvidia's. Banding wasn't too noticeable. If you use the VMR7 or VMR9 renderer the banding is almost unnoticeable. You should try that before re-encoding your video.

[foxyshadis]

If it's a cheap LCD, it'll probably be 6-bit TN, also. Even nowadays most of them are, and it exacerbates even the slightest banding in the source.

[Psythorn]

If it's a cheap LCD, it'll probably be 6-bit TN, also. Even nowadays most of them are, and it exacerbates even the slightest banding in the source.

Well it wasn't exactly cheap... But yes... It kinda looks like it...