[FFmpeg-devel] [PATCH] avfilter: add starfield video source

[Moritz Barsnick]

On Thu, Sep 07, 2017 at 21:29:33 +0200, Paul B Mahol wrote:
> Signed-off-by: Paul B Mahol <onemda at gmail.com>

Works fine for me.

>  libavfilter/Makefile         |   1 +
>  libavfilter/allfilters.c     |   1 +
>  libavfilter/vsrc_starfield.c | 191 +++++++++++++++++++++++++++++++++++++++++++

Missing some texi documentation.

> +static const AVOption starfield_options[] = {
> +    { "size",  "set video size",   OFFSET(w),          AV_OPT_TYPE_IMAGE_SIZE, {.str = "hd720"},   0,         0, FLAGS },
> +    { "rate",  "set video rate",   OFFSET(frame_rate), AV_OPT_TYPE_VIDEO_RATE, {.str = "25"},      0,   INT_MAX, FLAGS },

When using this, I immediately missed the usual vsrc option
abbreviations "s" and "r", respectively.

> +    { "stars", "set stars number", OFFSET(nb_stars),   AV_OPT_TYPE_INT,        {.i64 = 1024},      1,     81920, FLAGS },

"number of stars"?

> +    { "speed", "set speed",        OFFSET(speed),      AV_OPT_TYPE_RATIONAL,   {.dbl = 1.01},      1,         2, FLAGS },

Why 1.01 and not 1.0? (Just wondering.)

> +    .description   = NULL_IF_CONFIG_SMALL("Create retro 3D star field."),

Nice, "retro". :-) (I don't mind at all, I just had to giggle and
wonder why a star field would be considered retro.)

Functionally: The stars seem to jump from one pixel location to the
next, and not interpolate across pixels - very unsmooth and annoying.
This is quite obvious e.g. if you create the video at 360x240, and view
it several times as large. The anti-aliasing might be a future enhancement
though.

Other "features" might be configurable fore/background colors, star
size (is that random right now?), and stuff...

Question: Why do the stars appear white(-ish), although their R, G, B
components are each randomly initialized?

Moritz