[FFmpeg-devel] [PATCH] avfilter: add displace video filter

[Paul B Mahol]

On 11/7/13, Clement Boesch <u at pkh.me> wrote:
> On Wed, Oct 23, 2013 at 09:14:28PM +0000, Paul B Mahol wrote:
>> Signed-off-by: Paul B Mahol <onemda at gmail.com>
>> ---
>>  doc/filters.texi          |  43 +++++
>>  libavfilter/Makefile      |   1 +
>>  libavfilter/allfilters.c  |   1 +
>>  libavfilter/vf_displace.c | 390
>> ++++++++++++++++++++++++++++++++++++++++++++++
>>  4 files changed, 435 insertions(+)
>>  create mode 100644 libavfilter/vf_displace.c
>>
>> diff --git a/doc/filters.texi b/doc/filters.texi
>> index 7783807..0ba4e51 100644
>> --- a/doc/filters.texi
>> +++ b/doc/filters.texi
>> @@ -3100,6 +3100,49 @@ delogo=x=0:y=0:w=100:h=77:band=10
>>
>>  @end itemize
>>
>> + at section displace
>> +
>> +Displace pixels as indicated by second and third input stream.
>> +
>> +It takes three input streams and output one stream, the first input is
>> the
>
> It takes ... and outputS ...
>
>> +source and second and third input are displacement maps.
>
> is the source, and second and third ...
>              ^
>> +
>> +The second input specifies how much to displace pixels along the
>> +x-axis, while the third input specifies how much to displace pixels
>> +along the y-axis.
>> +
>
> Can you give an example with values? Assuming a pixel value between 0x00
> and 0xFF, it will displace it by [-127;127]?
>
> Can you use 10-bit maps to make larger displacement?
>
>> +A description of the accepted options follows.
>> +
>> + at table @option
>> + at item edge
>> +Set displace behavior for pixels that are out of range.
>> +
>> +Available values are:
>> + at table @samp
>> + at item blank
>> +Missing pixels are replaced by black pixels.
>> +
>> + at item smear
>> +Adjacent pixels will spread out to replace missing pixels.
>> +
>> + at item wrap
>> +Out of range pixels are wrapped so they point to pixels of other side.
>> + at end table
>> +
>> +Default is @samp{smear}.
>> +
>> + at end table
>> +
>> + at subsection Examples
>> +
>> + at itemize
>> + at item
>> +Add ripple effect to input of video size hd720:
>> + at example
>> +ffmpeg -i INPUT -f lavfi -i
>> nullsrc=s=hd720,geq='r=128+50*sin(2*PI*X/800):g=128+50*sin(2*PI*X/800):b=128+50*sin(2*PI*X/800)'
>> -f lavfi -i nullsrc=s=hd720,lutrgb=128:128:128 -lavfi '[0][2][1]displace'
>> OUTPUT
>
> I would suggest some annotation about the example. Also make it easier to
> get a working version. Something like:
>
>   ffmpeg -f lavfi -i testsrc=s=hd720 # your input video (here a filter
> source)
>         -f lavfi  -i
> nullsrc=s=hd720,geq='r=128+50*sin(2*PI*X/800):g=128+50*sin(2*PI*X/800):b=128+50*sin(2*PI*X/800)'
> # sinusoidal deformation for y-axis
>         -f lavfi -i nullsrc=s=hd720,lutrgb=128:128:128 # unchanged
> deformation source for x-axis
>         -lavfi '[0][2][1]displace' OUTPUT
>
> Q1: Can't you avoid the parameter copy for geq?
>
> Q2: What's the benefit of source videos maps over evals?
>     Maybe pre-computed maps to make it faster? If so, you should add
>     another complete workflow example where you generate maybe two
>     pictures pattern.
>
> Q3: Won't it be nice to have a 't' parameter to make it wave between sine
>     and original form?

?

>
> [...]
>> diff --git a/libavfilter/vf_displace.c b/libavfilter/vf_displace.c
>> new file mode 100644
>> index 0000000..65ba8d2
>> --- /dev/null
>> +++ b/libavfilter/vf_displace.c
> [...]
>> +AVFilter avfilter_vf_displace = {
>
> Don't forget to replace with ff_vf_displace.
>
> Code looks fine to me.
>
> [...]
>
> --
> Clement B.
>