[mythtv-users] Confusion about transcoding, Nuvexport / ffmpeg / mythtranscode

[Matt Mousseau]

Oh, one more thing, is either ffmpeg (that's what nuvexport uses to
actually do the transcode, right?) or mythtranscode multi-threaded? IE,
will they take advantage of a dual processor machine?

Matthew Mousseau
AMSVans, Inc. Webmaster
matt at amsvans.com


-----Original Message-----
From: mythtv-users-bounces at mythtv.org
[mailto:mythtv-users-bounces at mythtv.org] On Behalf Of Robert Tsai
Sent: Thursday, August 25, 2005 11:37 AM
To: Discussion about mythtv
Subject: Re: [mythtv-users] Confusion about transcoding,Nuvexport /
ffmpeg / mythtranscode


On Thu, Aug 25, 2005 at 08:09:48AM -0400, Matt Mousseau wrote:
> What exactly happens when I tell myth to "transcode" a recording from 
> the Watch Recordings screen? Previously to re-encode files I have used

> nuvexport, which I know is just a perl script that pulls information 
> about all your recordings from the database, checks dependencies, and 
> asks you how you want to re-encode specific files, then launches 
> ffmpeg. I'd like to utilize the built-in transcoder, but I'm curious 
> how it compares in speed to the nuvexport/ffmpeg combo.
>  
> Of course, I could have the complete wrong idea about how that 
> operates, soooo...can anybody give me some idea what happens when I 
> hit that little "X" key on my keyboard?

It will launch the internal "mythtranscode" transcoding program (which
is different from the "mtd" MythDVD transcoding program) to transcode
your TV recordings. Usually the motivation is to save space, but it can
also be used to cut out commercials (but nuvexport can also respect the
commercial cutlists).

It differs from nuvexport in that nuvexport will create a new file for
you (presumably for you to burn to DVD, or place in your permanent
MythVideo collection), while mythtranscode will replace your original
recording with the transcoded copy (by default; there is a backend
option to preserve the original files as ".old" or something like that).

I can't really compare with nuvexport; I used nuvexport once to burn a
DVD of a program. Otherwise, I pretty much always use mythtranscode to
save space.

>From the space-saving perspective, the only use I can really see for
mythtranscode is to save space when you don't have a capture card that
can do the desired transcoding at recording time. For example, I only
have two HD-3000 cards (which do no encoding), so to save space I have
to have them processed after the recording is finished.

If you have the Hauppauge PVR-x50 cards or similar hardware, you should
be able to just use the "Recording Profiles" to tell the PVR hardware to
encode to the desired quality/disk-space profile; you shouldn't have to
use mythtranscode.

I think I've read somewhere on these lists that mythtranscode is
optimized for speed (at cost of lower quality), while nuvexport is
optimized for quality (at the cost of slower speed). But I don't know
anything about that.

--Rob