[mythtv-users] Transcoding SD MPEG2 to H.264---recommendations?

Christopher Kerr mythtv at theseekerr.com
Mon Nov 29 09:07:00 UTC 2010


On Mon, Nov 29, 2010 at 7:52 PM,  <f-myth-users at media.mit.edu> wrote:
>    > Date: Mon, 29 Nov 2010 09:36:51 +1100
>    > From: Christopher Kerr <mythtv at theseekerr.com>
>
>    > I'm not doing this yet, but I'm planning to get such a thing going
>    > over the next few weeks to help manage the endless episodes of "Escape
>    > to the Country" and "Bargain Hunt" that are clogging up my harddrive.
>
>    > I plan to use HandbrakeCLI with the Transcode Wrapper Stub on the wiki.
>
> I had very bad results with Handbrake in a test yesterday---see below.
>
>    > Transcode times vary pretty wildly depending on the complexity of the
>    > job, but as a datapoint:
>
> What args are you using to Handbrake?  Or are you using something like
> ffmpeg directly?
>
>    > I'm using an i5 750 (quad core, currently overclocked to 3.8GHz per
>    > core, stock is 2.66) with 4GB of RAM.
>
>    > A high profile encode of PAL DTV material, using deinterlacing and
>    > denoising, runs at 2-3 times realtime using all 4 cores.
>
>    > If you trade off some filesize for speed, a more normal encode might
>    > run at 4-5 times realtime (or about 1.5 times realtime if run on a
>    > single core)
>
>    > At the best end of things, the low-complexity low-resolution iPhone
>    > preset with denoising runs at about 6-8 times realtime (ie. a 2 hour
>    > film takes 15-20 minutes)
>
> Those times look good; I tried a Handbrake test with PVR-250 input
> (interlaced NTSC, 720x480) on an Athlon 64 5400+ (2.8GHz?) and it ran
> at about real-time speed using its default settings but no auto-crop,
> and using 1.5 of the 2 cores.  (Apparently, it couldn't keep the other
> half of the second core busy.)
>
> However---the result was unusable.  The activity log was crammed full
> of "audio 192 time went backwards 0 ms, dropped 1 frames" and "video
> time didn't advance - dropped 1 frames" lines, and about halfway
> through the transcode, it suddenly went from claiming it had 20
> minutes to go, to done.  (It also said "sync: got 26887 frames, 60691
> expected", which might explain a thing or two.)  And the result, as you
> might expect, was a jumpy mess.
>
> I have no idea why this didn't work.  I'd have thought that the mpeg
> file produced by a PVR-250 seeing baseband NTSC from an STB would be
> about as easy as you could get.  I do have VBI CC enabled; I wonder if
> that extra info is confusing Handbrake.  Searching for those error
> messages with or without PVR and other likely terms hasn't yielded
> much that's usable, alas.
>
> (The Handbrake version was "svn3686", which is what you get if you're
> running Ubuntu 9.10  and add ppa:stebbins/handbrake-snapshots.  I have
> no idea if this is just a bad version or what.)
>
> Didn't matter whether cropping was on or off, or whether I used the
> default decomb or switched to fast deinterlace.
>
> P.S.  Other issue is how I'm going to display deinterlaced transcoded
> stuff on my Sony analog CRT; can any VDPAU-capable card output interlaced
> content?  I seem to recall asking exactly this question a year or two
> ago, but can't find it and can't remember the answer...  I'm guessing
> that anything with an S-Video output is also outputting interlaced,
> but...

I haven't yet used Handbrake on linux, only ever on Windows and Mac
OS, and I've never had any issues with it - in my experience, it's
worked perfectly.

Be interesting to see how it goes....

- Chris


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