PNG_FILTER_VALUE_NONE  238 libavcodec/pngdec.c     case PNG_FILTER_VALUE_NONE:
PNG_FILTER_VALUE_NONE  142 libavcodec/pngenc.c     case PNG_FILTER_VALUE_NONE:
PNG_FILTER_VALUE_NONE  556 libavcodec/pngenc.c                              PNG_FILTER_VALUE_NONE,
PNG_FILTER_VALUE_NONE  559 libavcodec/pngenc.c         s->filter_type = PNG_FILTER_VALUE_NONE;