[mythtv] Recording multiple channels on a single DVB transport

Gnome42 gnome42 at gmail.com
Mon Nov 13 17:41:01 UTC 2006


On 12/20/05, Daniel Kristjansson <danielk at cuymedia.net> wrote:

> To make a DTV recording we go through a few steps
>  1 close any existing access to DVB/HDTV file devices
>  2 open a signal monitor and wait for it to find our channel
>  3 open a recorder to record the program
>  4 wait for recording to end
>  5 close the recorder
>
> The TVRec states all center around a single recording so I wouldn't
> change that. But you can create multiple TVRec's per device but tell
> them that they share a single tuner.
>
> When someone wants to make a recording (the scheduler or the user)
> and it is on a TVRec with a shared tuner you check if the tuner is
> already in use. If it isn't you proceed normally. If not, then
> assuming the channel is on the same transport/frequency you skip
> step 1, and in place of step 2 you just check the PSIP/SI tables
> for your channel. For step 3 you share the file descriptor for the
> recorders, and instead of just closing the recorder in step 5 you
> need to reference count the file descriptor and only close it if
> you are the last one out (because recordings may end at different
> times).
>
> The DVB recorder requires an additional change to filter only the
> PIDS it should be recording, the HDTV recorder already handles this.
>
> The only real changes for when this topic has come up before is
> steps 1 and 2. So read up on those earlier discussions.

Hi Daniel and All,

I have been thinking my way through your list of how recordings are
done. I am stumped by how to handle this in the DeviceReadBuffer and
was hoping for some pointers/direction.

If there are multiple TVRec's (and each TVRec has a DVBRecorder and a
DeviceReadBuffer) for a DVB card how do we _share_ the TS data being
read from ../drv0 amongst the separate DeviceReadBuffers? Sharing the
file descriptor for the device doesn't help us does it?

Some sorta shared version of the DeviceReadBuffer with pid filtering?
Sounds too complicated, there must be a better way.

Shane


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