[mythtv-users] mencoder and re-encoding HDTV shows.

[Paul Mason]

On 18/09/2007, Paul Mason <latepaul at gmail.com> wrote:
>
>
>
> On 18/09/2007, jack snodgrass <mrlinuxgroups at gmail.com> wrote:
> >
> > I'm using this mencoder command to re-encode a HDTV show to something
> > smaller... something
> > I can stream to my office over the internet or something I can put on
> > a usb drive....
> >
> > mencoder -srate 22050 -vf scale=720:400 -oac mp3lame -lameopts
> > preset=15:mode=3 -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=900 -sws 2
> > -o /tmp/1005_20070914190000_720x400x900.avi
> > /mnt/store/1005_20070914190000.mpg
> >
> > This command takes 22 minutes or so to re-encode a 30 minute, 4GB HDTV
> > show down to
> > 101Meg at a reasonable quality ( compared to the original HD stream ).
> >
> > 22 minutes seems a bit excessive to me for a 30 minute show.... this
> > is on a E6600 Core Duo.
> > It takes 2-3 more minutes to do this same command on a AMD x86_64
> > 3800+ box... quite
> > a bit slower than the E6600 box.
> >
>
> I was thinking 22 minutes was quite impressive. My AMD 3800+ (non-dual)
> box was taking ~80mins to convert a 2Gb, 45min DVD ripped VOB file to h264.
> That's with an IVTC filter and then resize (720:480 -> 512:384). That was
> before I decided that it was a background task anyway and so I'd do a
> two-pass transcode which is now taking 2h15m per file.
>
> I'm using avidemux2_cli. I'd heard mencoder was quicker but I didn't think
> it was that much quicker. I might have a go with mencoder tonight.



Well that was a useful exercise, thank you. So after a little playing I
discovered that:

1) like-for-like[1] mencoder is slightly faster but only slightly so.

2) the x264 is significantly more cpu-hungry than FFmpeg4

3) for the same bitrate[2] x264 encodes a noticeably[3] nicer video but

4) for only a little (25%) more filesize I can have a similar quality
FFmpeg4-encoded file in less than half the time.

So, since disk is cheap and time is less so, I'm going to switch to using
FFmpeg. Though stick with avidemux2_cli as I prefer it, and mencoder did
some funny things with sound on one of my tests[4]

Oh and when testing with Jack's options above, this also re-inforced
something I already knew, namely that I can cope much more easily with lower
picture quality than audio. Seriously, it sounded like it was being played
underwater!



[1]or as close as I could get.
[2]my loose definition of 'same bitrate' is 'same resolution and target file
size'
[3]to me. YMMV.
[4]I'm sure I could've fixed it given time and enough googling -but why
bother when I have an alternative that already works fine?


-- 
Paul Mason
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