On Thu, Aug 20, 2020 at 04:50:05PM +0200, Nicolas George wrote:
> The channel_layouts and channel_counts options set what buffersink
> is supposed to accept. If channel_counts contains 2, then stereo is
> already accepted, there is no point in having it in channel_layouts
> too. This was not properly documented until now, so only print a
> warning.
>
> Signed-off-by: Nicolas George <geo...@nsup.org>
> ---
> libavfilter/buffersink.c | 23 +++++++++++++++++++++++
> 1 file changed, 23 insertions(+)
>
>
> Added an explanation requested by Paul.
>
>
> diff --git a/libavfilter/buffersink.c b/libavfilter/buffersink.c
> index 76a46f6678..c58daf6124 100644
> --- a/libavfilter/buffersink.c
> +++ b/libavfilter/buffersink.c
> @@ -62,6 +62,28 @@ typedef struct BufferSinkContext {
>
> #define NB_ITEMS(list) (list ## _size / sizeof(*list))
>
> +static void cleanup_redundant_layouts(AVFilterContext *ctx)
> +{
> + BufferSinkContext *buf = ctx->priv;
> + int nb_layouts = NB_ITEMS(buf->channel_layouts);
> + int nb_counts = NB_ITEMS(buf->channel_counts);
> + int l, lc, c, n;
> +
> + for (l = lc = 0; l < nb_layouts; l++) {
> + n = av_get_channel_layout_nb_channels(buf->channel_layouts[l]);
> + for (c = 0; c < nb_counts; c++)
> + if (n == buf->channel_counts[c])
> + break;
this would be O(nb_layouts * nb_counts) but can be done in
O(nb_layouts + nb_counts) as in
for (c = 0; c < nb_counts; c++)
has_channel_count[ buf->channel_counts[c] ] = 1;
for (l = lc = 0; l < nb_layouts; l++) {
n = av_get_channel_layout_nb_channels(buf->channel_layouts[l]);
if (has_channel_count[ n ])
break;
not sure this is faster or how much it is in practice or how much that matters
but its asymptotically better and its simple
thx
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
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