[mythtv-users] Max number of DVB channels per usb tuner

John Pilkington J.Pilk at tesco.net
Sat Dec 21 12:06:26 UTC 2013


On 21/12/13 11:40, Mark Perkins wrote:
> I was looking for something, don't remember what now, but came across
> the following statement on a site advertised as a complete guide to
> MythTV -
> http://www.techradar.com/news/software/applications/complete-guide-to-mythtv-947946/4
>
> ******
> If you're using DVB (either terrestrial or satellite), you're in luck,
> because these multiplex several channels into one stream. MythTV is able
> to receive an entire stream from a DVB tuner card, and then split it
> into individual programmes.
> When adding a capture card in mythtv-setup, press the Recorder Options
> button to see a further screen, which includes a Max Recordings setting.
> Three is a sensible setting for this, and means that you could record
> six channels at once if you have two capture cards.
> ******
>
> Is that statement correct - ie that the number of channels that can be
> tuned from a single multiplex is not a hardware "given" of the
> particular card / tuner (in a DVB context)?
>
> I've set mine to two per usb tuner but that was because I thought I
> remembered reading on the box (back when I had the box) that it was
> capable of two channels.

IIRC the default max number of 'virtual tuners' per hardware tuner is 5. 
  I have two single-tuner cards both set to that, and another USB tuner 
set to two.  I think the main reason for the 5 limit is to keep the 
scheduler complexity to a manageable level.  It's usually called 'multirec'.


>
> I've gone back to the manufacturer website to see what it says but it
> only has the following statement which I am not sure whether it means
> that it can tune two multiplexes (on a single usb tuner) and two
> channels from each multiplex, or 4 channels from a single multiplex.
>
> ******
> Multiple Video Processing mode, enables two TV tuner devices, up to four
> channel program processing simultaneously. You can simply upgrade your
> TV enjoyments with one more WinFast digital TV tuner card/ box for
> multiple TV viewing.
> ******
>
> No doubt there are other considerations (ie hardware of the backend) but
> I think USB 2.0 does 480Mbps and a multiplex is 20Mbps total so the USB
> part should be fine. I think a 7200rpm HDD can do around 60Mbps
> sustained write so that should be plenty as well.
>
>
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