avfilter/formats: allow unknown channel layouts by default

Since the default in the libav fork is to only allow known layouts, making unknown layouts allowed by default here can be a security risk for filters directly merged from libav. However, usually it is simple to detect such cases, use of av_get_channel_layout_nb_channels is a good indicator, so I suggest we change this regardless. See http://ffmpeg.org/pipermail/ffmpeg-devel/2016-November/203204.html. This patch indirectly adds unknown channel layout support for filters where query_formats is not specified: abench afifo ainterleave anullsink apad aperms arealtime aselect asendcmd asetnsamples asetpts asettb ashowinfo azmq It introduces a query_formats callback for the asyncts filter, which only supports known channel layouts since it is using libavresample. And it removes .query_formats callback from filters where it was only there to support unknown layouts, as this is now the default: aloop ametadata anull asidedata asplit atrim

MBMarton Balint committed 9 years ago