ffmpeg \
-ac 1 \
-i 'udp://a.b.c.d:1234?sources=w.x.y.z&fifo_size=2000000&overrun_nonfatal=1' \
-i 'udp://a.b.c.e:1234?sources=w.x.y.z&fifo_size=2000000&overrun_nonfatal=1' \
-i 'udp://a.b.c.f:1234?sources=w.x.y.z&fifo_size=2000000&overrun_nonfatal=1' \
-i 'udp://a.b.c.g:1234?sources=w.x.y.z&fifo_size=2000000&overrun_nonfatal=1' \
-threads 0 -max_alloc 5000000000 \
-filter_complex \
"nullsrc=s=720x576 [bas]; \
[0:a] aresample=icl=stereo:ocl=stereo:async=1000, anullsink; \
[0:v]drawtext=fontfile=/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf:text=a1:fontcolor=white:fontsize=80:borderw=3:x=(w-tw)/2:y=(th):box=0:boxcolor=0x000000, setpts=PTS-STARTPTS, scale=360:288 [ulv]; \
[1:v]drawtext=fontfile=/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf:text=a2:fontcolor=white:fontsize=80:borderw=3:x=(w-tw)/2:y=(th):box=0:boxcolor=0x000000, setpts=PTS-STARTPTS, scale=360:288 [urv]; \
[2:v]drawtext=fontfile=/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf:text=a3:fontcolor=white:fontsize=80:borderw=3:x=(w-tw)/2:y=(th):box=0:boxcolor=0x000000, setpts=PTS-STARTPTS, scale=360:288 [llv]; \
[3:v]drawtext=fontfile=/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf:text=a4:fontcolor=white:fontsize=80:borderw=3:x=(w-tw)/2:y=(th):box=0:boxcolor=0x000000, setpts=PTS-STARTPTS, scale=360:288 [lrv]; \
[bas][ulv] overlay=shortest=0:x=0 [dul]; \
[dul][urv] overlay=shortest=0:x=360 [dur]; \
[dur][llv] overlay=shortest=0:y=288 [dll]; \
[dll][lrv] overlay=shortest=0:x=360:y=288" \
 -c:v libx264 -crf 20 -preset ultrafast -aspect 16:9 -pix_fmt yuv420p -b:v 7M -an  -flush_packets 0 -mpegts_transport_stream_id 0x0001     -mpegts_service_id 0x0bba  -mpegts_start_pid 0x0bba -flags cgop+ilme -sc_threshold 1000000000 -f mpegts -muxrate 9M - | parser a.b.c.z 1234 l.m.n.o