PNG_FILTER_VALUE_NONE  191 libavcodec/pngdec.c     case PNG_FILTER_VALUE_NONE:
PNG_FILTER_VALUE_NONE  121 libavcodec/pngenc.c     case PNG_FILTER_VALUE_NONE:
PNG_FILTER_VALUE_NONE  432 libavcodec/pngenc.c     s->filter_type = av_clip(avctx->prediction_method, PNG_FILTER_VALUE_NONE, PNG_FILTER_VALUE_MIXED);
PNG_FILTER_VALUE_NONE  434 libavcodec/pngenc.c         s->filter_type = PNG_FILTER_VALUE_NONE;