From Opendigitalradio
Revision as of 12:37, 21 January 2022 by Hb9egm (Talk | contribs)

(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to: navigation, search

FDK-AAC-DABplus contains a DAB and a DAB+ encoder, which has been deprecated in favour of ODR-AudioEnc, which now integrates the codec in the same repository.

In september 2016, FDK-AAC-DABplus was split in three: ODR-AudioEnc, fdk-aac and ODR-PadEnc, for ease of maintainability and packaging, to clarify the licence situation a bit, and in the hope that the DAB+ modification to fdk-aac could be given upstream. This is unlikely to happen, and since ODR-AudioEnc is the only tool requiring the DAB+-capable fdk-aac, the codec was moved back into ODR-AudioEnc to simplify compilation and installation.

The DAB encoder is derived from libtoolame-dab. toolame-02l has been converted to a shared library libtoolame-dab.

The DAB+ encoder is derived from the Fraunhofer FDK AAC code from Android, patched for 960-transform and proper header and firecode.

The main tool is dabplus-enc, which can encode from a file or pipe source, all inputs supported by libVLC or an ALSA soundcard, and encode to a ZeroMQ output compatible with ODR-DabMux, to a file or to standard output. The VLC ALSA input supports experimental sound card clock drift compensation, that can compensate for imprecise sound card clocks.

To encode DLS and Slideshow data, ODR-PadEnc 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 different tools.

Its development is public : http://github.com/Opendigitalradio/fdk-aac-dabplus




The FDK-AAC-DABplus package depends on libfec, boost-thread, boost-system, alsa and ZeroMQ. For instructions on how to install these, please see ODR-DabMux#Prerequisites

The mot-encoder optionally needs ImageMagick's magick_wand to be able to resize pictures.


See https://github.com/Opendigitalradio/fdk-aac-dabplus#how-to-build


Several usage scenarios are shown in https://github.com/Opendigitalradio/fdk-aac-dabplus#how-to-use

Problem solving

In the case you are using ZeroMQ between the encoder and odr-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.

If you are using a pipe between the encoder and odr-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:

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.

Historical notes

The encoders were renamed at version 0.2.0. The aac-enc testing program disappeared, but its code is still in src/. The aac-enc-dabplus and aac-enc-dabplus-zmq were renamed to dabplus-enc-file and dabplus-enc-file-zmq. dabplus-enc-alsa-zmq appeared in v0.2.0.

In v0.2.2, dabplus-enc-file-zmq received support for output to file and pipe, making dabplus-enc-file obsolete, which has therefore been removed.

In v0.4.0, lots of code redundancy between different encoder variants has been merged into dabplus-enc. The old tools dabplus-enc-file-zmq, dabplus-enc-alsa-zmq and all this have been replaced by a single encoder.

Some of the encode- scripts available in the mmbtools-aux repository might still make use of the old names.

Personal tools