Re: TV recording quality stuck on best
From: Stephen Neal (stephen.neal_at_nospam.please.as-directed.com)
Date: 12/27/04
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Date: Mon, 27 Dec 2004 13:21:22 -0000
Roger48 wrote:
> Thanks for this helpful reply, Nigel. Yes, I do have a DVB-T card and
> had no idea it came with such restrictions.
It isn't a "restriction" as such - just a difference.
When MCE is used with an analogue capture device (such as a Hauppauge PVR)
the MPEG2 encoding is performed by the capture card itself, so you can
select your own compression levels (i.e. the quality setting in MCE). This
means you can trade-off recording quality for space - using a lower quality
to squeeze more onto a fixed capacity DVD-R for example.
When you use a DTV card (such as a DVB-T or ATSC card) the MPEG2 compression
is performed by the broadcaster as part of the broadcast process. The DVB-T
card just receives the MPEG2 signal and presents it to MCE 2005. MCE then
records it directly - or decodes it for live TV display. The bitrate, and
thus the quality level, is determined by the broadcaster not the capture
card or software. Therefore the amount you can record onto a DVD will vary
depending upon the data rate chosen by the broadcaster. The BBC use a fixed
rate of approx 4.8Mbs for BBC One in England, but BBC Two, Three/CBBC and
News 24 are "statmuxed" with each other - sharing a pool of data and varying
the data rate they are broadcast at based on dynamically assessing the
content of each channel. Typically this means they are broadcast at around
3-4.5Mbs depending on their (and the other two) channels content.
> I've always recorded at
> "best" quality and until recently have never needed to transfer to DVD
> more than about 90 minutes of TV recording.
How much you can fit onto a 4.7Gb DVD is likely to depend on the channel in
question - some run at higher or lower data rates than others - so the
amount of disc space required varies channel by channel!
> But over Christmas I
> recorded a couple of movies and wanted to store them, but the system
> couldn't cope with two hours so I tried to alter the quality setting.
> Media Center gives no clue as to why it won't let you change it.
>
Nope - MCE 2005 is a bit "basic" when it comes to DTV support.
> According to the Sonic Prime Time help facility, I should be able to
> record only 75 minutes on to DVD at best quality, but I have managed
> 90 on a couple of occasions.
>
I think this is based on the "analogue" Best setting - which is a fixed
rate. "Best" in terms of DTV (DVB and ATSC) effectively means "as
broadcast" - or "only" - in quality level terms.
> Thanks again for your intervention. I'm reassured that nothing's
> actually wrong; I'm just suffering a shotcoming in the system.
You can always, if you have the time and don't mind the quality reduction,
pull the DVR-MS Recorded TV files into a re-encoding application like
TMPEnc, which will allow you to decode the recorded TV files, and re-encode
them to MPEG2 at a fixed data rate, so that they fit into a fixed space?
(Personally I like the quality of DVB-T recordings to remain high, so
instead split long recordings between discs)
Steve
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