Sunday, September 25, 2011

MythTV archiving nowadays

I haven't mentioned MythTV in a long, long time, largely because I stopped messing around with either the hardware or software in that machine. Some months ago I attempted to upgrade the software but it kept failing before completion. Fortunately, the backup/restore feature allowed me to recover fairly easily each time. Between that difficulty and the extent by which the rest of my devices have since left the machine's hardware in the dust, I'd need to restart the entire project to do it properly. I'm not eager to expend the time, money, or energy for that (plus, the MythTV competitors are so much better now than back then...).

Regardless, it keeps working year after year, so I keep using it. When I seldom overrode the auto-delete of old recordings, my customary procedure for "archiving" was to run nuvexport to convert the source MPEG-2 file, captured/encoded by the PVR-350, into an XVid AVI. The result sometimes contained some bursts of unfortunate side effects, like small to medium "blocking", yet I thought this was a reasonable compromise for the sharply reduced storage requirements. Watching too closely yielded the impression of a video being portrayed by many tiny crawling ants. But quick and well-organized ants, I must admit, especially when seen from twice the usual viewing distance.

Recently, as I kicked off a nuvexport job and felt annoyed once again by the estimated time, I finally recognized the antiquated absurdity. The MythTV machine was put together using rather cheap parts that were current a few generations previously. My main Ubuntu desktop is a more modern computer with the corresponding increases in capability and performance. Moreover, my experiences with streaming services like Netflix or Amazon have reminded me of the advances in video compression. Time to rethink.

Instead, I've switched to transferring the source MPEG-2 from MythTV using the MythWeb interface's Direct Download, so the archiving work can exploit the newer hardware and software of the desktop. I run the h264enc script without many custom answers. The H.264 MP4 files look pretty good at around the same bitrate. And probably due to both the higher clock rate and additional specialized CPU instructions, the process really doesn't take that long to run: the stated output fps rate is faster than playback. This is despite the "nice" priority which prevents interference with all other tasks.

Of course, one "pre-processing" step remains in MythTV; I continue to employ the extremely easy interactive "Edit Recordings" feature (I've never trusted the automatic commercial detection). With the rapid "loss-less" option, the chosen edits produce just a shorter MPEG-2 file, ready for further manipulation elsewhere.

NOTE (Oct 1): Another side effect of switching to a video compression format that's conquered most of the world is that the Roku 2 supports it. But given that I have a working MythTV installation, this hardly matters...

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