ODR-PadEnc is an encoder for Programme Associated Data (PAD) and includes support for:

  • MOT Slideshow (including catSLS), according to ETSI EN 301 234 and TS 101 499
  • DLS (including DL Plus), according to ETSI EN 300 401 and TS 102 980

To encode DLS and Slideshow data, the odr-padenc tool reads images from a folder and DLS text from a file, and generates the PAD data for the encoder.

For detailed usage, see the usage screen of the tool with the -h option.

More information is available on the Opendigitalradio wiki

How to build


  • a C++11 compiler
  • ImageMagick MagickWand (optional, for MOT Slideshow), version 6 (legacy) or 7

To install MagickWand on Debian or Ubuntu:

sudo apt-get install libmagickwand-dev

To compile and install ODR-PadEnc:

sudo make install

ImageMagick and Ubuntu 16.04

Please note that Ubuntu 16.04 still (09.03.2017) ships a version of ImageMagick that was affected by a memory leak (see #2). Hence ODR-PadEnc will increasingly consume memory until it crashes!

Until Ubuntu backports the bugfix, you should therefore use a more recent version of ImageMagick (6.9.2-2 or higher).

Usage of MOT Slideshow and DLS

odr-padenc reads images from the specified folder, and generates the PAD data for the encoder. This is communicated through a fifo to the encoder. It also reads DLS from a file, and includes this information in the PAD.

If ImageMagick is available

It can read all file formats supported by ImageMagick, and by default resizes them to 320x240 pixels, and compresses them as JPEG. If the input file is already a JPEG file of the correct size, and smaller than 50kB, it is sent without further compression. If the input file is a PNG that satisfies the same criteria, it is transmitted as PNG without any recompression.

RAW Format

If ImageMagick is not compiled in, or when enabled with the -R option, the images are not modified, and are transmitted as-is. Use this if you can guarantee that the generated files are smaller than 50kB and not larger than 320x240 pixels.

Supported Encoders

odr-audioenc can insert the PAD data from odr-padenc into the bitstream. The mp2 encoder Toolame-DAB can also read odr-padenc data.

This is an ongoing development. Make sure you use the same pad length option for odr-padenc and the audio encoder. Only some pad lengths are supported, please see odr-padenc's help.

Character Sets

When odr-padenc is launched with the default character set options, it assumes that the DLS text in the file is encoded in UTF-8, and will convert it according to the DAB standard to the Complete EBU Latin based repertoire character set encoding.

If you set the character set encoding to any other setting (except Complete EBU Latin based repertoire which needs no conversion), odr-padenc will abort, as it does not support any other conversion than from UTF-8 to Complete EBU Latin based repertoire.

You can however use the -C option to transmit the untouched DLS text. In this case, it is your responsibility to ensure the encoding is valid. For instance, if your data is already encoded in Complete EBU Latin based repertoire, you must specify both --charset=0 and --raw-dls.

Known Limitations

odr-padenc encodes slides in a 10 second interval, which is not linked to the rate at which the encoder reads the PAD data. It also doesn't prioritise DLS transmission over Slides.

Some receivers are unable to decode slides larger than some size, even within the allowed size limit given in the specification.


This encoder was initially called mot-encoder and has been contributed by CSP.