DAB/DAB+ encoding

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Revision as of 21:17, 27 December 2011

Encoding the sound to MPEG-2 Layer II for DAB, MPEG-4 HE-AACv2 for DAB+ or video in MPEG-4 H.264 for T-DMB before feeding it to the multiplexer.

Contents 1 DAB audio encoding with toolame 1.1 jack input 1.2 Old workaround needed for JACKless toolame 2 DAB+ audio encoding with crc-dabplus 2.1 jack input 3 Tools for data services encoding 4 Decoding Internet stream 4.1 mpg123 input 4.2 mplayer

DAB audio encoding with toolame

• toolame MPEG-Layer II encoder (DAB)

jack input

Toolame has been modified to support JACK, rendering the dirty workaround mentioned below unnecessary.

Example:

toolame -D 4 -b 128 -j -n toolame1 ./1.ff

Old workaround needed for JACKless toolame

Toolame doesn't support jack, we use arecord with ALSA emulation to get the raw PCM stream. It is a dirty workaround, it is foreseen to find a better way in the future for example by modifying toolame to support jack:

Example:

arecord -t raw -f S16_LE -c 2 -r 48000 -D jackplug |toolame -s 48 -D 4 -b 128 /dev/stdin ./1.ff

DAB+ audio encoding with crc-dabplus

• CRC-dabplus HE-AAC encoder (DAB+) from CRC (warning, it is not free/open source because of royalty)

Example streaming one radio and with a buffer to compensate for bursty output from encoder

crc-dabplus -i souphttpsrc://location=http://maxxima.mine.nu:8000 -g -m -c 2 -b 48 -o file:///dev/stdout |mbuffer -m 100k -P 100  >output_fifo 

jack input

crc-dabplus uses Gstreamer for input/output.

Example of jackplug input (ALSA emulation), encoding at 48kbps, output to a FIFO file:

crc-dabplus -i card://jackplug -g -c 2 -b 48 -o file://2.ff

Similar example but with DLS input from TCP on port 12000

crc-dabplus -i card://jackplug -g -c 2 -b 80 -d tcpserver://:12000 -p 28 -t dls -o file://4.ff

Tools for data services encoding

• CRC-SlideShow : slideshow generator from CRC.
• DAB-EPG API from Global Radio Labs (never tested)

Decoding Internet stream

Here are some simple way to get internet radio stream as input and decode them into raw PCM samples to feed DAB/DAB+ encoders

mpg123 input

"mpg123" can be used to take Internet radio stream and convert them from mp3 to raw PCM samples. Be careful, it has been noticed that earlier version have a memory leak when resampling. We use version 1.4.3 to avoid the problem.

Example that decode an mp3 stream, resample it to 48kHz and output the raw samples to stdout:

mpg123 -b 1024 -r 48000 -s http://maxxima.mine.nu:8000

mplayer

simple mplayer command for jack output

mplayer -ao jack http://maxxima.mine.nu:8000