With the recent guide issues I’m having with TiVo, I’m looking at purchasing a Plex Pass and moving to the Plex DVR as that still has Gracenote guide data (which is an improvement in my area over the Rovi data). One item, however, would be how focused thumbnail generation can be. Most items in my Plex library don’t need thumbnail generation (and the space/server hit that brings). However, in a Plex DVR world there are some items that would be of benefit. Morning news shows and daily chat shows, for example, are programs that my wife currently does a lot of fast-forwarding through until she sees something on-screen that she wants to see. She rarely watches them straight through and usually burns through the bulk of them on the weekend using this fast-forward ‘catch-up’. She would definitely not buy-in to changing to Plex DVR without the visual cues on screen.
I’m assuming Plex DVR works the same as my current Plex library in that fast-forward of recorded shows doesn’t show that visual cue without thumbnail generation. As I don’t need thumbnail generation for the entire library of TV shows (thus saving the space and server load during generation) - but would need it for her daily news/chat shows - is it possible to have Plex only generate thumbnails on specific programs? I wouldn’t care if it was even a manual task I had to initiate. Or is the only solution to have recorded TV in its own library? This wouldn’t be ideal as I would prefer to have the recorded shows placed in the same TV library as already exists for ease of ‘unwatched’ filtering.
VPTs can also be generated automatically when material is added, or both when added and during scheduled maintenance determined by the settings at:
Plexweb/Settings/Server/Library/
*Run a partial scan when changes are detected [Checkbox]
*Generate Video Preview Thumbnails [Options]
Triggering ‘When Added’ is surrounded a bit by mystery and intrigue to be determined if your libraries are located on local drives (just works) or Network Shares. <---- wherein the automatic detection routine is a complete crap shoot.
Those ‘in the know’ instinctively and manually update a network share when adding media manually and when material is automatically added (I would assume this happens in the Plex DVR world) a manual update is performed when new material that should be there, isn’t. This is the mystery and intrigue bit.
Anyway - once new material is found (one way or another) if the setting allows, VPTs will be generated.
Before enabling VPTs it would be wise to inspect the free space on the OS drive to ensure there is Plenty - as in PLENTY. If not, now would be an excellent time to change ‘The path where local application data is stored’ at: Plexweb/Settings/Server/General/
to a location on a separate LOCAL drive (bolted in the server box) with ample free space - and it is noteworthy to mention this procedure can be described as painful and result in the rediscovery of your entire Plexiverse if not done juuuuuuust right.
So it is only on a per-library setting. One can’t do it for only certain entries. So it looks like I would have to separate Recorded TV from TV Shows at the library level to prevent thumbnails being created for the entire library.
That is correct.
Having your Recorded TV in a Dedicated Library isn’t a bad thing really. I have 4 Dedicated Libraries for Recorded TV - two for TV Shows and Two for Movies.
You should also be aware that VPT generation will absolutely, positively pin your CPU to the ceiling for the duration of generation. This process, per item, could finish in moments, minutes or hours depending on CPU horsepower and quality/size of material requiring thumbs. It is for this reason I also recommend a VISUAL inspection of the CPU cooling apparatus to ensure free air flow and regular maintenance of same.
You wouldn’t want to fry your box and have to explain to the Wife why we’re buying another one well before it’s agreed upon and scheduled upgrade window. That could cost you in ways you are only now trying to imagine. 
Bingo! That did the trick. I was able to successfully generate thumbnails for only one show through the command line – without turning it on for an entire library - and without needing to separate the desired item from the rest of the library. It worked great! I assume there is no indicator inside of Plex to see progress of the task? I was able to determine start/finish through CPU usage in task manager - but just curious if the task is viewable like optimized version tasks. I don’t believe this is the case - but wanted to check. Anyway - thanks again for the command-line option. It exactly fits the bill for the few shows it would be needed if TiVo is abandoned.
And one final question I forgot to ask: As thumbnail creation would only be used for wife’s daily shows that we don’t keep - if a file is deleted either through client delete dialog or if I simply delete the folder in the library, when Plex realizes the file is no longer there, does Plex cleanup the thumbnails generated so they don’t take up space?
There is no way of tracking the progress of the thumbnails. The final BIF file is stored with the rest of the metadata for the video. Once a video is removed and the library is updated to reflect that, the metadata and BIF will be tagged for removal. You can manually remove these by selecting Clean bundles from the home page in Plex Web or they can be done automatically as part of the scheduled tasks, ‘Remove old bundles every week’.
