fate: add apng encoding/muxing test

Also test the fallback to png creation for a single frame.
Reviewed-by: NJames Almer <jamrial@gmail.com>
Signed-off-by: NAndreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>

tests/fate/avformat.mak

 FATE_LAVF-$(call ENCDEC,  PCM_S16BE,             AIFF)               += aiff
 FATE_LAVF-$(call ENCDEC,  PCM_ALAW,              PCM_ALAW)           += alaw
+FATE_LAVF-$(call ENCDEC,  APNG,                  APNG)               += apng
 FATE_LAVF-$(call ENCDEC2, MSMPEG4V3,  MP2,       ASF)                += asf
 FATE_LAVF-$(call ENCDEC,  PCM_S16BE_PLANAR,      AST)                += ast
 FATE_LAVF-$(call ENCDEC,  PCM_S16BE,             AU)                 += au

tests/lavf-regression.sh

@@ -212,6 +212,15 @@ do_avconv $file $DEC_OPTS -f image2 -vcodec pgmyuv -i $raw_src $ENC_OPTS -t 1 -q
 do_avconv_crc $file $DEC_OPTS -i $target_path/$file -pix_fmt rgb24
 fi
 
+if [ -n "$do_apng" ] ; then
+file=${outfile}lavf.apng
+do_avconv $file $DEC_OPTS -f image2 -vcodec pgmyuv -i $raw_src $ENC_OPTS -t 1 -pix_fmt rgb24
+do_avconv_crc $file $DEC_OPTS -i $target_path/$file -pix_fmt rgb24
+file=${outfile}lavf.png
+do_avconv $file $DEC_OPTS -f image2 -vcodec pgmyuv -i $raw_src $ENC_OPTS -pix_fmt rgb24 -frames:v 1 -f apng
+do_avconv_crc $file $DEC_OPTS -i $target_path/$file -pix_fmt rgb24
+fi
+
 if [ -n "$do_yuv4mpeg" ] ; then
 file=${outfile}lavf.y4m
 do_avconv $file $DEC_OPTS -f image2 -vcodec pgmyuv -i $raw_src $ENC_OPTS -t 1 -qscale 10

tests/ref/lavf/apng

+a4c46fad7716ad094eb3c78b74ca0244 *./tests/data/lavf/lavf.apng
+6209864 ./tests/data/lavf/lavf.apng
+./tests/data/lavf/lavf.apng CRC=0x87b3c15f
+c5900fdd1b2fc30b985793f5226fd0c4 *./tests/data/lavf/lavf.png
+248854 ./tests/data/lavf/lavf.png
+./tests/data/lavf/lavf.png CRC=0xd8c7b7a1