[FFmpeg-devel] [RFC] libswscale and non-chroma-aligned slices

Michael Niedermayer michaelni
Sat Jan 9 18:20:03 CET 2010

On Sat, Jan 09, 2010 at 05:40:36PM +0100, Stefano Sabatini wrote:
> Hi all,
> libswscale issues slices with weird heigth, for example:
> y:100 h:9
> y:119 h:9
> y:128 h:10

try again, this doesnt look very likely

> this with an yuv420p output, so I'd expect for each slice an height
> which is a multiple of vsub^2, that is:
> h == (h & ~((1 << vsub) - 1));
> For example for the previous case I'd rather expect:
> y:100 h:8
> y:118 h:10
> y:128 h:10
> I suppose the chroma components lines associated to the last luminance
> line is already filled, anyway it would be a lot simpler to make the
> scaler always return already chroma-aligned h values, this would
> simplify the logic required from each filter dealing with such slices,
> which gets complicated especially with negative slice direction
> values.

you have a video of yuv420p with vertical resolution of 9
how exactly will you avoid outputing a slice of odd height?

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The educated differ from the uneducated as much as the living from the
dead. -- Aristotle 
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