[Ffmpeg-devel] lowres

Roine Gustafsson roine
Sun May 22 02:28:56 CEST 2005

On May 21, 2005, at 11:32 PM, Michael Niedermayer wrote:
> On Saturday 21 May 2005 15:32, Roine Gustafsson wrote:
>> "-lowres 1" seems broken in ffmpeg. It either produces a
>> full-resolution frame with a incorrect lowres image in it, or breaks
>> with segmentation fault in draw_edges_c. It doesn't seem to take in
>> account that the resulting image will be smaller.
> did it ever work better? if yes then when did it break?

I've never tried ffmpeg's -lowres before. My code broke with lowres and 
I wanted to check lavc (turned out to be unrelated).
Your patch improves ffmpeg's lowres but doesn't fix it.

I assumed it worked at some point :)

>> Shouldn't there be some attribute you can query if a codec supports
>> lowres or not?

Well? Something like a CODEC_CAP_LOWRES.

>> Also, I get quite alot of artifacts with lowres on high motion parts
>> that touches edges (both in mplayer and in my code). Is this a known
>> limitation of lowres or a bug?
> did it work better in the past? if no then without further info i 
> would say
> its a limitation, which shouldnt mean its impossible to improve though 
> ...

For most video it's very good. I don't think it's been better before 
I have an anime clip that is pretty revealing. I've uploaded a snippet 
to MPlayer's incoming as "difficult_lowres.avi".
Play with e.g. "mplayer -lavdopts lowres=1 difficult_lowres.avi".


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