[x264-devel] Boundary constraints

[Etienne Bömcke]

On 21 Nov 2007, at 14:48, Loren Merritt wrote:

> On Mon, 19 Nov 2007, Etienne Bömcke wrote:
>
>> I've got another question for you concerning the definition of the
>> boundary constraints within the encoder. Here's the deal : I've got
>> two video sequences, encoded separately. The first one is of  
>> classical
>> dimension, 720x576 for example, and the second one is a banner, let's
>> say 200x576. My goal is to incorporate the second sequence in the  
>> firt
>> one, replacing the bottom 200 lines with the banner. In order to do
>> that I need two things :
>> - I have to manipulate the bitstream to replace the sequence bottom's
>> macroblocks with the banner's macroblocks.
>> - The sequence has to be encoded without any prediction from the
>> bottom area, neither spatial nor temporal.
>>
>> As for now I'm focusing on the second part, ideally I'd like to be
>> able to define a mask defining the sequence areas where prediction is
>> allowed and feed it one way or another to the encoder. I suppose I'll
>> have to modify the code where the boundary constraints are checked.
>>
>> I just wanted to have a quick evaluation from people who know this
>> code better than I do. Do you think it could be done?
>
> You have control over the encoding process, and want to encode two  
> videos such that they can be either viewed separately or later  
> losslessly merged?

The idea would be to have one basis video, one part of which could be  
replaced by various banners, depending on the viewing context.

>
>
> Do your banners go only on the bottom of the frame, or would you  
> ever want to replace e.g. the left side? Your example is  
> inconsistent: 200x576 would be a side.

You're right about the dimensions, it was a mistake. I meant something  
like 720x150. As for now I only need bottom banners, but if there's a  
way to do this with any part of the sequence that would be way better.

> This is important bause you really don't want to implement it  
> without slices, and slices normally only stack vertically.


I'm afraid I don't really understand this... I thought about using  
slices, but as x264 currently doesn't support slices I was wondering  
if there was another way to achieve that goal. When you say slices  
only stack vertically, are you talking about that patch of yours you  
were mentioning in a former mail?

Once again, thanks a lot for your answers.

>
>
> --Loren Merritt_______________________________________________
> x264-devel mailing list
> x264-devel at videolan.org
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--
Etienne Bömcke
UCL - Laboratoire TELE
etienne.bomcke at uclouvain.be