DAB/DAB+ multicast streamer — modelled after dvblast, for digital radio.

Receives a DAB/DAB+ ensemble from an SDR device and streams each radio service as an individual MPEG-TS/UDP multicast stream, one per service. Each stream carries a single audio programme with full DVB PSI tables (PAT, PMT, SDT, EIT) and DLS (now-playing text) updates.

RTL-SDR (or compatible SDR)
         │
         ▼
   OFDM demodulator
   (frequency sync, FFT, Viterbi)
         │
         ▼
   DAB multiplex decoder
   (FIC → ensemble/service info)
   (MSC → subchannel audio data)
         │
         ▼
   DAB+ superframe filter
   (Reed-Solomon FEC, LATM audio)
         │
         ▼
   MPEG-TS packetiser
   (PAT + PMT + SDT + EIT + audio PES)
         │
         ▼
   UDP multicast  239.x.x.x:port

One UDP multicast stream is sent per configured service. VLC, mplayer, ffmpeg, and IPTV clients can tune each address directly.

sudo apt install \
  build-essential cmake \
  librtlsdr-dev \
  libfftw3-dev \
  libfaad-dev \
  libmpg123-dev

Optional:

• libairspy-dev — Airspy HF+ support
• libSoapySDR-dev — generic SDR support via SoapySDR

cmake -B build -S .
cmake --build build -j$(nproc)

Optional build flags:

Scan a single frequency:

./dablast -f 202928000 --scan

Or scan multiple frequencies in one pass using a frequency list file:

./dablast -l /etc/dab-Brisbane.freqs --scan

Example /etc/dab-Brisbane.freqs:

197648000 # 8B
202928000 # 9A
204640000 # 9B
206352000 # 9C
208064000 # 9D

dablast will scan each frequency in turn, printing results to stdout and progress/status to stderr. Frequencies with no DAB signal are skipped.

Output example (stderr):

Ensemble found. Collecting service list...
Ensemble: DAB+ Brisbane 1 (9A)  EId 0x1006  202928000 Hz

Output example (stdout):

MMM 80s:202928000:0x12A5
HeartHits:202928000:0x12A7
Inspire Digital:202928000:0x12CD
Coles CBD:202928000:0x1259
GOLD 80s:202928000:0x126D

Each line maps a service to a multicast address:

# /etc/dablast-202928000.conf
# Format: MULTICAST_IP:PORT  SERVICE_ID  # optional comment
239.2.2.1:20000  0x12A5  # MMM 80s
239.2.2.2:20000  0x12A7  # HeartHits
239.2.2.3:20000  0x12CD  # Inspire Digital
239.2.2.4:20000  0x1259  # Coles CBD
239.2.2.5:20000  0x126D  # GOLD 80s

dablast -f 202928000 -c /etc/dablast-202928000.conf

Tuning:
  -f FREQ      Centre frequency in Hz  (e.g. 202928000)
  -l FREQFILE  File of frequencies to scan (one per line)

Hardware:
  -a INDEX   Adapter/device index (default: 0)
  -F DRIVER  Input driver: rtl_sdr (default), rtl_tcp, soapysdr
  -g GAIN    RF gain in tenths of dB, or -1 for AGC (default: -1)

Modes:
  --scan     Scan ensemble and print service list, then exit
  -c FILE    Config file for streaming mode

Other:
  -h         Show this help

Run one instance per DAB ensemble (frequency). Each instance uses one SDR device:

dablast -f 197648000 -a 0 -c /etc/dablast-197648000.conf &
dablast -f 202928000 -a 1 -c /etc/dablast-202928000.conf &

# VLC
vlc rtp://@239.2.2.1:20000

Or add the multicast addresses to any IPTV playlist (M3U).

dablast passes audio through from the DAB multiplex without re-encoding — the audio quality is exactly what the broadcaster transmits.

DAB+ requires a specific decoder to play at full quality. Here is what HE-AACv2 actually does and why it can go wrong:

• The broadcast transmits a mono AAC core at 24 kHz — this is the base layer
• SBR (Spectral Band Replication) reconstructs the upper frequencies, bringing the output up to 48 kHz
• Parametric Stereo (PS) reconstructs the stereo image from the mono core, giving full left/right stereo

A decoder that handles all three layers correctly will output full 48 kHz stereo. A decoder that only reads the base layer will output 24 kHz mono — noticeably thin and low quality.

Desktop VLC works correctly because it uses FAAD2, a decoder specifically built for DAB+ that handles 960-sample AAC frames and the full HE-AACv2 chain.

Many other players (Android apps, hardware IPTV boxes, some media servers) use hardware AAC decoders or general-purpose software decoders that do not support the 960-sample frame size used by DAB+. These will fall back to the 24 kHz mono base layer regardless of how the stream is signalled. This is a decoder limitation, not a problem with the stream itself — the stream content is correct.

There is no workaround short of transcoding the audio on the receiving end, to decode and re-encode to a standard 1024-sample AAC stream.

• RTL-SDR — any RTL2832U-based USB dongle (default, tested)

The following drivers are included from the welle.io backend and should work in principle, but have not been tested with dablast:

• Airspy HF+ — compile with -DAIRSPY=ON
• SoapySDR — any SoapySDR-supported device, compile with -DSOAPYSDR=ON
• rtl_tcp — network-attached RTL-SDR via rtl_tcp server, use -F rtl_tcp
• Raw IQ file — for testing, use -F rawfile

Copyright (C) 2026 Paul Stanley paul.stanley@tutanota.com

GNU General Public License v3.0 or later — see LICENSE.md.

This project incorporates code from welle.io, SDR-J, DABlin, and third-party libraries. See LICENSE.md for details.