View source for FDK-AAC-DABplus

This is open-source version of DAB+ encoder. fdk-aac-dabplus reads audio data from standard input, and outputs data on standard output. The second tool fdk-aac-dabplus-zmq outputs frames using ZeroMQ, which can be used with the inputZmq from [[CRC-DabMux]]

== Installation ==
===Prerequisites===

fdk-aac-dabplus depends on libfec.

fdk-aac-dabplus-zmq depends on libfec and ZeroMQ.

For instructions on how to install these, please see [[CRC-DabMux#Prerequisites]]

===Building===

 git clone https://github.com/mpbraendli/fdk-aac-dabplus.git
 cd fdk-aac-dabplus
 ./bootstrap
 ./configure --enable-example --enable-zmq
 make
 sudo make install

Remove the flag --enable-zmq if you don't want to compile fdk-aac-dabplus-zmq

If the bootstrap step fails, you can try
 autoreconf -i
instead.


==Usage==
===Encoding===
After successful installation, it can be used to encode DAB+ in several ways.

Encoding of audio input, output to fifo:
 ALSASRC="default"
 BITRATE=64
 
 sox -t alsa $ALSASRC -b 16 -t raw - rate 48k channels 2 | \
   ../fdk-aac-dabplus/aac-enc-dabplus \
   -i /dev/stdin -b $BITRATE -f raw -a -o -o /dev/stdout 2>/dev/null | \
   mbuffer -q -m 10k -P 100 -s 360 > station1.fifo

Encoding of audio input, output to crc-dabmux using ZeroMQ
 ALSASRC="default"
 BITRATE=64
 DST="tcp://your.dabmux.example.com:9000"
 
 sox -t alsa $ALSASRC -b 16 -t raw - rate 48k channels 2 | \
   ../fdk-aac-dabplus/aac-enc-dabplus-zmq \
   -i /dev/stdin -b $BITRATE -f raw -a -o $DST

Live Stream enconding and preparing for DAB mux:
 arecord -t raw -f S16_LE -c 2 -r 48000 -D plughw:CARD=Loopback,DEV=0,SUBDEV=0 | \
 aac-enc-dabplus -b 24 -f raw -c 2 -r 48000 -i /dev/stdin -o /dev/stdout 2>/dev/null | \
 mbuffer -q -m 10k -P 100 -s 360 > station1.fifo

Wave file enconding and preparing for crc-dabmux:
 aac-enc-dabplus -a -b 64 -i wave_file.wav -o station1.dabp

Also have a look at the ''encode-'' scripts available in the [[https://github.com/mpbraendli/mmbtools-aux mmbtools-aux repository]]

===Problem solving===
If you are using a '''pipe between the encoder and crc-dabmux''', and you see a lot of errors like this:
 <2> ERROR: Incomplete DAB+ frame! 136 != 360
 <5> reach end of file -> rewinding
 <2> ERROR: Can't rewind file
 <6> ETI frame number: 228

Then the stream has to be buffered before giving it to muxer, this additional buffer installed between encoder and fifo. To calculate proper block size for mbuffer ("-s" parameter), the table below may be used:

{| border="1" cellpadding="5" cellspacing="0"
!DAB+ Stream bitrate, kbps
!Block size, bytes
|-
|16
|240
|-
|24
|360
|-
|32
|480
|-
|48
|720
|-
|56
|840
|-
|64
|960
|-
|72
|1080
|-
|128
|1920
|-
|160
|2400 
|}

In example above, for stream with bitrate 24 kbps, mbuffer size set to 360 bytes. This trick helping to solve problem.


In the case you are using '''ZeroMQ between the encoder and crc-dabmux''', and you see errors that the size of the data is wrong, then the configured bitrate in the mux probably doesn't correspond to the bitrate given to the encoder. Make sure they are identical.