[FFmpeg-devel] [PATCH] avfilter: add dynoverlay filter.

[wm4]

On Thu, 22 Sep 2016 18:45:43 +0000
"Priebe, Jason" <jpriebe at cbcnewmedia.com> wrote:

> This patch adds a new filter that allows you to drive dynamic graphic overlays
> on a live encoding by creating/updating/deleting a specified 32-bit PNG.
> This is very different from the overlay filter, because it lets you change
> the overlay in real time during a live stream.  It doesn't allow you to overlay
> video on top of video, but you can overlay still images over video, which is
> useful for things like lower-thirds and fullscreen graphics.

This seems like a very odd approach, and the filter seems to have very
limited usefulness.

Why can't this be a bit more general? Like providing an API to set
overlay images, and letting ffmpeg.c use it to e.g. load from a file in
intervals. Rather than hardcoding yet another CLU use-case in the libs.

We already have a long list of filters that seem to hardcode such
things.

Most importantly, it definitely shouldn't duplicate any blending code.

> +
> +static unsigned long long get_current_time_ms (void)
> +{
> + unsigned long long ms_since_epoch;
> + struct timespec spec;
> +
> + clock_gettime(CLOCK_REALTIME, &spec);

Unportable.

> +
> + ms_since_epoch =
> + (unsigned long long)(spec.tv_sec) * 1000 +
> + (unsigned long long)(spec.tv_nsec) / 1.0e6;
> +
> + return ms_since_epoch;
> +}
> +
> +static int load_overlay (AVFilterContext *fctx)
> +{
> + DynOverlayContext *ctx = fctx->priv;
> +
> + AVFrame *rgba_frame;
> +
> + struct stat attrib;
> + int ret;
> +
> + if ((ret = stat(ctx->overlayfile, &attrib)) != 0)

Not sure if portable.