Record multiple channels from one multiplex

DVB transmissions can send multiple content streams (channels) on a single multiplex (frequency) meaning that one tuner can record multiple channels at once, where those channels are on the same multiplex. In the UK, where multiplexes can carry ten or more channels, it would be incredibly useful.

Multiplex recording also allows overlapping of sequent recordings of the same program. That avoids the annoying problem with the end of a broadcast being in the next recording or the beginning of a broadcast being at the end of a previous recording.

This currently can't be done in MythTV.

Countries with multiplexed DVB/ATSC transmissions

Australia

• ABC and ABC2, with ABC2 repeating much of the ABC content later in the week (great if you run out of tuners)
• SBS with SBS world News
• Digital 44 (Sydney only) - datacasting of news/tab/expo/christian tv/parliament

Europe

• Astra 19.2° and EutelSat 13.0° DVB-S (up to 20 radio or 8 TV programs per transponder/multiplex)

Germany

• All TV stations on DVB-C/-T (4 TV programs per VHF/UHF multiplex)

UK

The UK is made up of 6 multiplexes. As you can see below, with only 6 tuners you could have quite an incredible MythTV recording platform.

Mux 1	Mux 2	Mux A	Mux B	Mux C	Mux D
BBC ONE	ITV1	abc1	301	E4+1	Film4
BBC TWO	ITV2	bid tv	302 / Community	Sky Sports	Ideal World
BBC THREE	ITV3	Five	305	Sky Sports News	ITV Play
BBC NEWS 24 / CBBC	CITV	Five Life	BBC FOUR / CBeebies	Sky Three	The HITS
	Channel 4	Five US	BBC News Multiscreen	UKTV History / smileTV	TMF
	E4	price-drop tv	BBC Parliment		UKTV Bright Ideas / f tn
	More 4	QVC
	Quiz Call	Teachers' TV

The full list can be found here: [1]

Feel free to reformat or move the above data if you feel it's too big or not relevant for this page.

Pledge

A pledge to pay a developer who implements this feature has started.

• Hints for implementation:
  • Grab the complete TS from a DVB device
  • Fork a transport stream demuxer process for each recording
  • Make sure to handle process signals correctly (no zombies) to prevent mythtv-backend crashes when receiving broken transport streams.
  • Use source type (DVB-C/-S/-T), frequency and polarisation (DVB-S) to identify programs on the same multiplex in the recording scheduler.

Discussions

Please read these discussions, and the Trac ticket thoroughly before starting a new discussion about the subject on the mailing list.

• is mythtv smart enough to do this with recordings? thread on mailing list
• One mux, multiple channels - status? thread on mailing list
• Recording 2 channels on same multiplex (HDHomerun) thread on mailing list
• Record >1 channel per multiplex? thread on mailing list
• Handle multiple DVB channels simultaneously from a single multiplex thread on mailing list.
• Trac ticket

If someone has time, it would be great if the ideas in these threads and the ticket could be summarised?

Documentation

• PDF version of the Linux DVB API version 3

Software Engineering

Testing Phase

Testing by Users ;-)