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

Robert Tsai rtsai1111 at comcast.net
Thu Aug 25 17:27:34 UTC 2005


On Thu, Aug 25, 2005 at 11:56:18AM -0400, Matt Mousseau wrote:
> My system (will) use moto 6200's w/fire wire inputs... Sooo
> 
> The transcoding is to save space. 
> 
> Basically, I'm get my system to:
> 1. Record the program (basically just dump the mpeg stream from the
> firewire to disk if I'm not mistaken)
> 2. Wait till I flag the commercials
> 3. Transcode to xvid, divx, or whatever (cutting commercials) (hopefully
> would start automatically once commercials flagged)
> 4. Move the newly transcoded file to /mythtvArchive (on a separate raid
> set)
> 5. Create a symlink in the /mythRecordings to the transcoded file in
> /mythArchive

Yes, what you describe above is possible using either mythtranscode or
nuvexport. Yes, you can automatically start mythtranscode or nuvexport
after commercials are flagged, and move files around, and create
symlinks.

What you fail to realize is that commercial flagging is not always
100% correct, so if you go automatically cutting commercials you risk
losing real content.

> -----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
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