Forked welle.io for DAB+ linear recording

This project is a simplified fork of welle.io

Goals

• Learn the official welle.io codebase
• Learn how a DAB+ mux works
• Be focus only on the cli tool and rtl-sdr support
• Adapt the code to be able to record 24/7 a whole ensemble or only selected service(s)
• Be able to extract audio stream (decoded PCM and native AAC) + DLS + MOT
• if people are interested in these specific features, propose back some patchs ans pull requests to the official welle.io project

Why a fork ?

welle-cli command from welle.io project is great but I didn't find a way to do some specific things:

• How to selected some services out of an ensemble ?
• How to specify a record path ?
• How to extract the raw ACC stream ?
• How to avoid aac -> PCM -> mp3 decoding/recoding ?

So I began this fork. Of course with free GPL licence.

Differences / Usage

• Choose a block. arg -c. ex: -c 5A
• Choose the service(s) to decode. arg -s + serviceIds comma separated, ex: -s f00d,f00e
• Choose base storage directory. arg -o. ex: -o /path/to/rec
• Files name are bases on serviceId rather than serviceLabel.
• Audio streams are decoded and recorded in .pcm file (raw without any header, 48kHz, stereo, 16 bits)
• Metadata are stored in new line delimited json format (extension .ndjson)
• MOT pictures are stored with their original extension (png ou jpg), with a timestamp in the file name
• Tree structure (f00d = serviceId in hexa)
  • /path/to/rec/$serviceId/$serviceId.pcm
  • /path/to/rec/$serviceId/$serviceId.ndjson
  • /path/to/rec/$serviceId/$serviceId-$timestamp-MOT.[jpg|png]
• Ability to use several SDR keys to records more than one ensemble on a same machine (tested by 2)

Installation

Debian

sudo apt install cmake g++ librtlsdr-dev libfftw3-dev

MacOS

brew install cmake mpg123 fftw librtlsdr

Compilation

cd welle.io
mkdir build
cd build
cmake ..
make
sudo make install

About DAB+ ensemble

A DAB+ multiplex, or mux, or ensemble, is identified by a central frequency, in MHz BHF Band III is splitted in blocks, or channels width 1536 kHz bandwidth.

Paris current active blocks are the following :

Block	Frequency	EnsembleLabel
5A	174.928 MHz	EXPE TDF TFL 5A
6A	181.936 MHz	PARIS 6A
6C	185.360 MHz	towerCast-m1
6D	187.072 MHz	PARIS 6D
8C	199.360 MHz	towerCast-m2
9A	202.928 MHz	RNT Associative
9B	204.640 MHz	PARIS 9B
11A	216.928 MHz	PARIS 11A
11B	218.640 MHz	Paris-Etendu

An ensemble gather the following properties :

• ensembleId (ex: F001)
• ensembleLabel (ex: Paris-Etendu)
• A service list

A service is caracterised by :

• serviceId (ex: FEED)

• serviceLabel (ex: RADIO LiFE)

• an audio stream (codec HE-AAC, 960 frames / sec), 88 à 128 kbps, mono or stereo, 48 kHz. We'll decode in WAV PCM 16 bits stéréo 48 kHz

• DLS (Dynamic Label Segment) : 128 bytes, utf-8 encodec

The dynamic label feature provides short textual messages which are associated with audio programme content for display on receivers. The messages can have any length up to a maximum of 128 bytes; depending on the character set used, the message can have up to 128 characters. https://www.etsi.org/deliver/etsi_en/300400_300499/300401/02.01.01_60/en_300401v020101p.pdf

• MOT Slideshow (image)

Multimedia Object Transfer, JPEG ou PNG 320x240 (ou +), ClickThroughURL (512 octets)

https://www.etsi.org/deliver/etsi_ts/101400_101499/101499/02.02.01_60/ts_101499v020201p.pdf

Launch a recording session

In the conf directory, create a profile, ex 5A.ini file with this kind of content :

REC_DIR="/Users/gus/dab"
BLOCK="5A"
SERVICES=("F00D:239.0.0.1" "F00E:239.0.0.2")

rec.sh script uses named pipes. welle-cli will write into these pipes (2 for each service), but an application has to read these whole pipes at the other side, otherwise there will be a buffer overflow. So you have to arm these readers before launch welle-cli.

read-pipe.sh simple script could be used to read these pipes. We could launch in parallel these commands:

./read-pipe.sh /Users/gus/dab/f00d/f00d.pcm
./read-pipe.sh /Users/gus/dab/f00d/f00d.ndjson
./read-pipe.sh /Users/gus/dab/f00e/f00e.pcm
./read-pipe.sh /Users/gus/dab/f00e/f00e.ndjson

Now execute rec.sh which do some checkes (and create named pipes) before the real welle-cli launch.

% ./rec.sh ./conf/5A.ini
- Autostart:
- Simu:      0
- Config:    ./conf/5A.ini
- Storage:  /Users/gus/dab
- Block:     5A
- Services:  F00D,F00E
- Create directory /Users/gus/dab/f00d
- Create named pipe /Users/gus/dab/f00d/f00d.pcm
- Create named pipe /Users/gus/dab/f00d/f00d.ndjson
- create directory /Users/gus/dab/f00e
- Create named pipe /Users/gus/dab/f00e/f00e.pcm
- Create named pipe /Users/gus/dab/f00e/f00e.ndjson
Did you arm all the recorders for selected services ? (y/N)
y
- welle-cli launch
---
InputFactory:Input device:auto
RTL_SDR: Open rtl-sdr
...

Synchronisation is done and named pipes start to be written (so as the MOT files). You can stop the process with Ctrl+C.

Misc

Read a named pipe, ingested by a raw pcm stream, with ffplay

cat f201.pcm | ffplay -f s16le -ar 48k -ac 2 -

Visualize shared libraries for a binary

MacOS

$ otool -L welle-cli
welle-cli:
	/usr/local/opt/librtlsdr/lib/librtlsdr.0.dylib (compatibility version 0.0.0, current version 0.6.0)
	/usr/local/opt/fftw/lib/libfftw3f.3.dylib (compatibility version 10.0.0, current version 10.10.0)
	/usr/local/opt/faad2/lib/libfaad.2.dylib (compatibility version 3.0.0, current version 3.0.0)
	/usr/lib/libc++.1.dylib (compatibility version 1.0.0, current version 1300.23.0)
	/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1311.100.3)

Linux

$ ldd welle-cli
	linux-vdso.so.1 (0x0000007faefa1000)
	librtlsdr.so.0 => /usr/local/lib/aarch64-linux-gnu/librtlsdr.so.0 (0x0000007faee76000)
	libfftw3f.so.3 => /lib/aarch64-linux-gnu/libfftw3f.so.3 (0x0000007faed19000)
	libfaad.so.2 => /lib/aarch64-linux-gnu/libfaad.so.2 (0x0000007faeccb000)
	libasound.so.2 => /lib/aarch64-linux-gnu/libasound.so.2 (0x0000007faebbe000)
	libpthread.so.0 => /lib/aarch64-linux-gnu/libpthread.so.0 (0x0000007faeaac000)
	libstdc++.so.6 => /lib/aarch64-linux-gnu/libstdc++.so.6 (0x0000007fae8d4000)
	libm.so.6 => /lib/aarch64-linux-gnu/libm.so.6 (0x0000007fae829000)
	libgcc_s.so.1 => /lib/aarch64-linux-gnu/libgcc_s.so.1 (0x0000007fae805000)
	libc.so.6 => /lib/aarch64-linux-gnu/libc.so.6 (0x0000007fae68f000)
	libusb-1.0.so.0 => /lib/aarch64-linux-gnu/libusb-1.0.so.0 (0x0000007fae663000)
	/lib/ld-linux-aarch64.so.1 (0x0000007faef71000)
	libdl.so.2 => /lib/aarch64-linux-gnu/libdl.so.2 (0x0000007fae64f000)
	libudev.so.1 => /lib/aarch64-linux-gnu/libudev.so.1 (0x0000007fae618000)

Ressources

• https://aerogus.net/posts/diffuser-tele-radio-reseau-local/#radio-dab-plus
• https://aerogus.net/posts/radio-dab-welle-cli/
• https://aerogus.net/posts/enregistrer-multiplex-radio-dab/
• https://github.com/aerogus/welle-cli
• https://github.com/AlbrechtL/welle.io
• https://fr.wikipedia.org/wiki/Bandes_de_fr%C3%A9quences_de_la_t%C3%A9l%C3%A9vision_terrestre