[mythtv-users] Transcoding all recordings to h.265

James Abernathy jfabernathy at gmail.com
Wed Nov 2 11:17:03 UTC 2022

On Wed, Nov 2, 2022 at 1:37 AM George Bingham <georgeb1962 at gmail.com> wrote:

> On Fri, Jun 4, 2021 at 8:56 AM Ryan Patterson <ryan.goat at gmail.com> wrote:
>> On Mon, May 24, 2021 at 10:29 AM Fred Hamilton <fred at yonkitime.com>
>> wrote:
>>> I've been using MythTV for 13 years, but never looked into transcoding,
>>> partly because I didn't want any quality loss, but also because most people
>>> seemed to be using it to create smaller files with the commercials cut out,
>>> and from normal watching I found commercial detection to be amazing but not
>>> reliable that I would trust it not to delete actual content.  (Although it
>>> looks like it might be much better nowadays - I watched SNL [usually a real
>>> challenge] last night and it did a flawless job.)
>>> But what I'd like to do now is transpose all of my multi-terabyte
>>> recording collection from .ts to h.265 mp4 (or similar), hopefully keeping
>>> the commercials in but keeping the commercial cutlist (although maybe it
>>> wouldn't be a bad idea to re-detect all the commercials with the latest
>>> algorithm).
>>> Is that doable from within MythTV?
>> In the past people have presented arguments that it was actually more
>> expensive to pay for the electricity to transcode recordings smaller, and
>> cheaper to spend the same amount to buy larger hard drives.  I'm not sure
>> what the math says is the optimal solution these days.
>> _____________
>> Ryan Patterson
>> May the wings of liberty never lose a feather.
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> I've never had luck with mythtv's built in transcoding feature. I've tried
> it up to in v31, but have not tried in v32. However I wanted to do
> something similar for shows I wanted to keep / archive, which nowadays is a
> small percentage of recorded content.
> Generally for a show I want to keep, I will edit the commercial skips so
> they are accurate, and usually watch the original recording at least once
> to make sure all the cuts are correct. If I still want to save it, I have a
> job setup to save it, one for movies and one for tv shows - they're a
> little different because for movies I want to keep I don't want any
> reduction in recording quality, but for tv shows where my goal is to
> archive a whole season at a time, I compromise and reduce from 1080 to 720,
> I also include season and episode numbers in the naming scheme.
> I run that job against only select recordings. They're stored so they
> appear under the Videos section in mythtv.
> What you are proposing where you want to transcode the whole recording,
> but keep the skip list intact probably won't work. At least I've never been
> able to make that work because transcoding usually removes or invalidates
> the seektable. You may be able to regenerate a new seek table on the
> transcoded recordings, but then I would think you'd have to re-run
> commercial flagging, and I don't know if that'd work on a file that's not
> an mpeg2 recording. Although I guess I don't really know if that's the case.
> Also the other respondent may be correct in that the amount of time and
> resources you spend on getting all your recordings transcoded may  be worth
> more than the expense of buying additional storage.
I don't transcode every show to h.264 m4v, but I do sometimes collect a TV
series that is a classic I want to have permanently. I have not had the
built-in transcoding work for years and the help I've received on this
mailing list has not helped me get it to work.

But I do use a User Jobs with a bash script that takes the .ts MPEG2
recordings and removes the commercials I've automatically flagged and then
manually corrected where they were not completely accurate and transcode
the TV show to h.264 m4v file and puts it on the NAS section of my
mythtv-backend so all mythfrontends can find it their Video category. This
allows me to keep the original .ts file until I'm sure I'm happy with the
.m4v file. The script job that I use has a quality factory that controls
the size/quality of the compression.  My current setting allows a 2GB
recording to be reduced to ~400MB.

As has been said before with the cost of storage that should not be the
reason to compress. I compressed and edited all the commercials of "The Big
Bang Theory". All 278 episodes now fit on a 256GB USB key I can throw in my
briefcase at a cost of $30.  Because I used a higher quality compression
factor than was really necessary I only reduced the size by a factory of
2.  So I could have kept all 278 episodes in MPEG2 on a 512GB USB key for
$64. My backend uses a mess of 4TB ($75) hard drives in a RAID
configuration. So in today's world, I'd just leave it in the original

One case I could see I might need this is when frontend devices can't
accelerate MPEG2 and aren't fast enough to do the decompression in OpenGL.
The script I use is from the one on the Mythtv Forum and I just modified
it. It's called sendTVtoNAS. You can start with that or I'll email you
directly what I use.


Jim A
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