[x264-devel] x264-devel Digest, Vol 19, Issue 23

[Ram prasad]

Thank you Dark
To begin with i'll use a variable where ever 420 is assumed. so that i can
encode 444 also.
Now, is there any thing I need to modify in the decoder side.
If yes please direct to a good decoder.
Thank you

On Tue, Dec 23, 2008 at 4:30 PM, <x264-devel-request at videolan.org> wrote:

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> Today's Topics:
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>   1. Lossless H.264 encoding (Ram prasad)
>   2. Re: Lossless H.264 encoding (Jason Garrett-Glaser)
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> Message: 1
> Date: Tue, 23 Dec 2008 15:26:14 +0530
> From: "Ram prasad" <ramprasad85 at gmail.com>
> Subject: [x264-devel] Lossless H.264 encoding
> To: x264-devel at videolan.org
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> Hi allMy source data is raw 24 bit RGB VGA video. I want to encode it into
> a
> h.264 video. my requirement is that this should be a lossless compression.
> Looking at the code i think x264 does not support any other format other
> than YUV 420. I am planning to modify the code to make it work on high
> quality YUV 444 or if possible on the RGB data itself.
> Before i embark on this task i would like to know whether it is feasible or
> not. if it is yes, how much effort would it require.
> Please share your thoughts.
> Thank you
>
> Regards
> Ramprasad N
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> Message: 2
> Date: Tue, 23 Dec 2008 05:05:24 -0500
> From: "Jason Garrett-Glaser" <darkshikari at gmail.com>
> Subject: Re: [x264-devel] Lossless H.264 encoding
> To: "Mailing list for x264 developers" <x264-devel at videolan.org>
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> 2008/12/23 Ram prasad <ramprasad85 at gmail.com>:
> > Hi all
> > My source data is raw 24 bit RGB VGA video. I want to encode it into a
> h.264
> > video. my requirement is that this should be a lossless compression.
> Looking
> > at the code i think x264 does not support any other format other than YUV
> > 420. I am planning to modify the code to make it work on high quality YUV
> > 444 or if possible on the RGB data itself.
> > Before i embark on this task i would like to know whether it is feasible
> or
> > not. if it is yes, how much effort would it require.
>
> RGB support is probably not feasible; I don't even know if the spec
> supports it, and even if it does, I know of no decoders that do--you'd
> have to modify a decoder to support it to, and you'd probably end up
> having to use the Separate Chroma Plane coding feature, where each
> chroma plane is its own image.
>
> YUV444 is definitely feasible.  It would require the following changes:
>
> 1.  In all cases where chroma planes are handled, instead of >>1 to
> get the size of chroma, or chroma stride, or whatever, a variable
> would have to be used.  This is probably the most time consuming step
> by far--going through all the code, finding all places where 420 is
> assumed, and fix it.
> 2.  AFAIK, a different Hadamard transform is used for chroma coding
> for 422/444.  This isn't important in lossless mode, but it would have
> to be implemented for the feature to be accepted (since lossy is also
> useful...).  It probably wouldn't be much work though.  In fact, if
> I'm right, you might be able to just use the luma transform for chroma
> in 444, as I think they might be the same.
> 3.  Deblock would have to be called on more chroma edges accordingly.
> Not important in lossless, but would be needed for lossy.
> 4.  Increase the size of the necessary dct blocks in x264_t to add
> enough room for all the chroma DCTs and adjust CABAC/CAVLC coding as
> necessary.
>
> Dark Shikari
>
>
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> End of x264-devel Digest, Vol 19, Issue 23
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