[FFmpeg-devel] [RESEND][PATCH] Fix buffer allocation in pad filter

[Andrey Turkin]

Sure; no-copy padding was broken for some scenarios (namely, left-padding
when target height divides evenly by 32). Lets say I want to use following
filter string: "scale=720x576, pad=880:576:80:0" (scale to 720x576 and add
some black bands on the sides). Pad should be able to allocate buffer for
scale and then just fill remaining area; yet it fails to do so and "Direct
padding impossible allocating new frame" message can be seen in logs (when
log level set to verbose). In this particular case the allocated buffer is
big enough to hold 896x576 image and a few extra bytes; scale filter then
operates on its view of the buffer (720x576 but with pitch of 896).
Interestingly, last row of that view doesn't fit in the buffer (there's
only 720 bytes + a bit of padding and not 880 bytes). So scale does its
thing and then pad checks if there is enough extra space in the buffer for
the padding. There's not; in fact there's no room in the buffer to hold the
view itself - so pad gives up and does another allocation and a copy. So,
basically this patch fixes that.

2016-01-06 0:59 GMT+03:00 Paul B Mahol <onemda at gmail.com>:

> On 1/5/16, Andrey Turkin <andrey.turkin at gmail.com> wrote:
> >
> > One extra line must be allocated when adding left padding to make sure
> > that last line in every plane fits in the allocated buffer fully
> > ---
> >  libavfilter/vf_pad.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> >
>
> Do you have example this patch fixes?
>