[mythtv-users] MPEG-2 to MPEG-4 Transcoding comparisons
Clif Deanhardt
mythtv at deanhardt.com
Wed Oct 29 02:28:21 EST 2003
Actually, I'm just trying to make it as small as possible (while,
unfortunately, knowing as little as possible). Back when I had the CVS
running (early september) I had it transcoding 3.7gb files into 700Mb
MPEG-4s with no noticable loss in picture quality (to my eyes). I can't
seem to recapture that, though.
I assume I'd just drop my MPEG-2/DEFAULT bitrate to 2200 or so and check the
quality... is that right? Should I expect to get any space savings from
converting a 2200 MPEG2 into a 2200 MPEG4? I have no reason to use MPEG4
other than trying to save space.
Clif
-----Original Message-----
From: James L. Paul [mailto:james at mauibay.net]
Sent: Wednesday, October 29, 2003 1:39 AM
To: Discussion about mythtv
Subject: Re: [mythtv-users] MPEG-2 to MPEG-4 Transcoding comparisons
Clif Deanhardt wrote:
> Would someone who's using .12 to transcode PVR-250 MPEG-2s into MPEG-4s
like
> to compare notes on compression rates? I'm trying to get a handle on
> whether I've got mine set up optimally and I'm a bit of a noob at setting
> this thing up.
>
> With the exception of a apparition when I first started using it, every
one
> of my 1hr shows records at 3.7gb and after transcoding it's 2.2gb,
> regardless of the type of show or number of colors or quantity of
movement.
I wonder... Is the quality of a 3.7G MPEG2 file transcoded to 2.2GB
MPEG4 better or worse than just encoding the original MPEG2 at 2.2G in
the first place? I have trouble believing it's better quality and worth
the effort, unless for some reason you really want the results as MPEG4.
> Likewise, every one of my half hour shows records at 1.8gb and transcodes
to
> 1.1gb.
My PVR-250 bitrate is set to result in 1 hour for 1.8G and looks
absolutely great, better than VHS to my eye. I just keep the MPEG2 and
prefer not to transcode at all. Then again, I have little use for MPEG4.
> Is anyone else similarly set up? What numbers are you getting?
>
> Thanx!
>
> Clif
>
>
> My settings:
>
> ----------------------------
> MPEG-2 ENCODERS / DEFAULT
> ----------------------------
> Width/Height: 480x480
>
> Codec: MPEG-2 HARDWARE ENCODER
> Stream: MPEG-2 PS
> Aspect: 4:3
> Bitrate: 4500
> Max Bitrate: 6000
>
> Codec: MPEG-2 HARDWARE ENCODER
> SampleRate: 32000
> Type: Layer II
> Bitrate: 384kbps
>
> ----------------------------
> TRANSCODERS / MPEG2
> ----------------------------
>
> Width/Height: 480x480
>
> Codec: MPEG-4
> Bitrate: 2200
> Max Quality: 2
> Min Quality: 15
> Max Quality Difference Between Frames: 3
> Scale Bitrate for Frame Size: Selected
> Enable High Quality encoding: Not Selected
> Enable 4MV: Not Selected
>
> Codec: MP3
> SampleRate: 32000
> Quality 7
>
> ----------------------------
> GENERAL
> ----------------------------
> It's configured to automatically detect commercials, but not to skip them.
> And the resulting, compressed files still have the commercials in them.
>
>
>
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