x264 with RGB32 input

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x264 with RGB32 input

Postby IchiCC » Sun Feb 15, 2009 5:55 am

Hey all. I have an RGB32 video that I'd like to encode using x264. However, for some reason it is always converted to the YV12 color space, resulting in quality loss. I'd like to know whether it's possible to encode in RGB32 using x264.

I have been using Zarx264gui if that's any help.
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Re: x264 with RGB32 input

Postby The Origonal Head Hunter » Sun Feb 15, 2009 8:20 am

No. If you use Zarxgui, it will HAVE to convert to YV12.
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Re: x264 with RGB32 input

Postby IchiCC » Sun Feb 15, 2009 8:35 am

Well, can I keep the RGB colors if I use something else?
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Re: x264 with RGB32 input

Postby Qyot27 » Sun Feb 15, 2009 8:52 am

No, H.264 itself doesn't support it. Distribution formats are generally YUV-only, if not strictly YV12. The only exception may be really harshly compressed MJPEG (but who would want to use MJPEG for distribution, anyway?).

Can you see the quality loss after it converts to YV12, and are you certain that loss isn't the product of your other compression settings? That's really the important question here. Colorspace conversions, while technically constituting a loss of quality via having to translate the channel info (and the fact that RGB can't be translated one-one to YUV or vice-versa, there's rounding errors), don't typically start showing the quality loss unless you've gone through several rounds of conversions back and forth.
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Re: x264 with RGB32 input

Postby IchiCC » Sun Feb 15, 2009 9:12 am

Hmm, well I'm compressing the raw file directly - it hasn't been compressed before. The resulting file seems to have noticeably duller colours, and seeing as the only thing that changed was a conversion to YV12, I assumed that that was the reason. I'll try to post some screenshots of what I'm on about. It might just be a naturalresult of simply compressing to H264.

EDIT: I just took two comparison screenshots, one of the input and one of the output, but it seems that the differences don't show up in them. I have no idea why that may be, there is most definately a noticeable difference when playing the actual video. Any advice?
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Re: x264 with RGB32 input

Postby Qyot27 » Sun Feb 15, 2009 9:39 am

The duller colors may be more a product of the video renderer being used, rather than the video or the colorspace conversion itself. Video renderer differences are also probably the root of the screenshot issue - it could be that those are set on one renderer, and the video player is set on another.
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Re: x264 with RGB32 input

Postby Zarxrax » Sun Feb 15, 2009 11:39 am

If you use Media Player Classic, you can go into the options and set the video renderer that is used for playback. I don't know which other players support this.
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Re: x264 with RGB32 input

Postby IchiCC » Sun Feb 15, 2009 2:43 pm

Hmm, well I'm not really sure what I did differently this time, but I've managed to obtain two screenshots of the problem. I'd really appreciate if someone could diagnose it.
Original:
http://img6.imageshack.us/img6/6546/rawvc8.png
After encoding:
http://img23.imageshack.us/img23/791/encodedyt9.png
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Re: x264 with RGB32 input

Postby Zarxrax » Sun Feb 15, 2009 6:05 pm

Its the renderer.
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