Maximum number of audio services ODR-DABMUX

[Lion Century]

Hi,

Is there a maximum number of audio / MOT services for the ODR- DABMUX, or is it all releated to the maximum of CU's?

Thanks,

Lion

[Matthias Brändli]

Hi

The maximum number of CUs is the hard limit. In practice, it's also
limited by expectations of offering a good audio quality, which imposes
a lower limit on the effective bitrate per service.

Independently, one could argue that above a certain number of services
it becomes challenging to respect the FIG repetition rates given in the
spec, but in my opinion, if you reach this number of services in a mux,
the audio quality of these services is already below acceptable.

mpb

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[Nick Piggott]

Hi,

One of the UK Trial Multiplex operators (Manchester) (http://www.wohnort.org/DAB/ukloc.html#Manchester%20Mini) has had over 20 services on it. The majority are at 48kbps HE-AAC v2.

There's been criticism of the audio quality of the services (which may not be entirely due to the bitrate used for transmission). The operator also struggled to stay within the *recommended* (not mandatory) repetition rates for the core FIGs in FIC.

The theoretical limit is very high - restricted by the 64 services limitation (assuming there's a justification for transmitting services at 16kbps HE-AAC).

DAB is a very flexible platform, but using it to excess in either direction (very low or very high bitrate services) is an inefficient use of spectrum and of low value to listeners. A pragmatic balance between variety and quality benefits everybody - but "variety" and "quality" are subjective assessments, not recommended or mandated by standards.

Nick

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[Lion Century]

Thanks,

Good  info.

I have look why my testmux is not working anymore after adding the 17 channel.

CU load is within limits, ODRdabmux is running, but stream to Modulator is no good, since the modulator stop putting out RF.

Just deleting the 17th channel ( and its services ) solves tjhis matter..

Thanks,

Lion

Op woensdag 5 september 2018 08:48:55 UTC+2 schreef Lion Century:

[pswiatki]

I would say it depends on what you exactly mean by number of audio services, or MOT services.

Check this figure from ETSI EN 300 401 V2.1.1 (2017-01):

I presume, you do not mean services / service components as seen in the service list on the receiver (where one can see many entries if MUX contains many service components pointing to exactly the same content), but rather entities carrying different content, right?

If so, I would point to this fact: 

So, you can only address up to 64 sub-channels (IDs 0 through 63), so this is also a limiting factor.

Some MOT content (SLS?) might be put into PAD, so that would give more combinations, but then - when in PAD - such MOT content isn't independent from the audio content.

Nevertheless, you seem to hit some limit internal to the software if it fails when you add 17-th sub-channel to the MUX....

[Lion Century]

Thanks! I will work with this!

Lion

Op woensdag 5 september 2018 18:42:25 UTC+2 schreef pswiatki: