Live TV in MythTV 0.19 and Beyond
One of the big changes to MythTV starting with 0.19 is how it handles Live TV. This page will try and outline How live TV works now, the advantages, and why you shouldn't have any fears over this new method.
You may be asking "But Isaac, WHY did you change how Live TV works? It worked fine for me in 0.18!"
The new method allows users to more easily record a show that they are watching in Live TV. It basically treats Live TV as a series of continuous scheduled recordings. This allows you to hit record at anytime and Myth will add the show to the Watch Recordings listing in its entirety.
The new Live TV method is also faster to change channels (for many users), and lowers hardware requirements a bit. The old style of Live TV involved an extra network transfer stage for all of the recording data, even for a single machine.
How It Works
Live TV now behaves like a series of scheduled recordings. When you enter Live TV MythTV begins recording the channel as though it were a scheduled recording, except that it flags it as LiveTV in its database. If you change channels MythTV does the same on the new channel, stopping the old recording, changing channels and recording the new channel. MythTV creates a recording file according to the scheduled recording rules for recordings (Why will become clear further down) and adds this file and the show information to its database of recorded shows. As the show you are watching ends, Myth stops writing to that file and creates a new file, and new database entry for the next show, in same vein of it thinking of it like a scheduled recording, except flagged as Live TV.
Now this is the cool part. MythTV is now treating what you're watching as a scheduled recording, so if you decide you actually want to keep what you're watching and hit the "Record" button all MythTV has to do is flag the recording in its database as no longer being just Live TV but an actual recording. It will now show up in your Watch Recordings listing!
There is some more to this. If you are watching LiveTV and exit to the menu, MythTV will stop recording to this Live recording. But if you hit record while watching and exit to the menu it will continue recording the show, as one would expect, until it finishes. So if you have multiple tuners and decide you want to record what you're watching and watch something else you can!
This feature allows you to exit from the MythTV Frontend while the MythTV Backend continues to record the show that's already in progress.
No programme guide: 30 Minute Segments
If there is no programme guide for the channel you are watching in LiveTV, Mythtv ends the recording automatically on the hour and 30 minutes past the hour, but it continues to record the programme in a new file. For example if you watch a channel without a programme guide in Live TV from 9.12 until 10.22, you will get three recording files: one starting at 9.12, one starting at 9.30 and one starting at 10.00.
You can press the left arrow key on the keyboard to rewind the programme while Mythtv is still recording it and Mythtv will rewind past the 30 minute segment it was in and seamlessly start on the previous 30 minute segment without interruption. If you press the left arrow key down long enough, Mythtv will finally arrive at the starting position of your LiveTV session, meaning that all of the 30 minute segments that were recorded are seen as one continuous file to Mythtv. This behaviour does not work if you are watching the programme from the Media library (outside LiveTV): to navigate seamlessly, you will have first to define a playlist of all the 1/2 hour recordings.
- But now I've got all these random recordings on my harddrive, won't it fill up and delete shows I've asked to record?: The answer of course should be, and is, No! MythTV will automatically expire recordings flagged in the database as LiveTV first before removing shows you scheduled to record.
- What about the old Live TV ring buffer drive I created?: You don't need it any more, Live TV now uses your recordings drive.
- Won't my recordings drive fill up faster now?: Yes.
- What if I share my recordings drive with other files? How can I ensure I always have free space?: Easy, use the Auto Expire Free Disk Space Threshold setting to tell MythTV you would like for there always to be XX amount of space on the drive!
- What if I do have enough free space, will MythTV keep these files until it needs to remove them?: No, by default MythTV will remove these Live TV recordings after 1 day. You can increase this period to longer if you would like. Remember, if MythTV sees it needs to create space on the hard drive it will remove these files sooner than one day!
It would be nice if someone who has a better understanding of exactly what MythTV is doing describes it here.
Reports of problems with LiveTV appear frequently without a fix appearing. However that may have changed as of February 2014. Jean-Yves Avenard has done a lot of work on LiveTV which can be seen on Trac ticket #12045 The updates can be found on 0.27-fixes.