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Recorded programs are very large in size
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Author:  NTolerance [ Wed Oct 11, 2006 10:49 am ]
Post subject:  Recorded programs are very large in size
I am using a Happauge WinTV GO card to record shows. A 60-minute program takes up nearly 4GB of disk space. Is it possible to reduce the size of these shows without degrading my already crappy recording quality?
Author:  ceenvee703 [ Wed Oct 11, 2006 11:52 am ]
Post subject: 
Adjust your recording profile (it's buried in some menu path I can't recall right now). There are four profiles set up by default: default, live tv, high quality, and low quality.

If your recordings are 4GB/hr, that sounds like your recording profile is cranked up to 8Mbps for video. This is high for MPEG2. Lowering that bitrate will reduce the quality of the recording, unless you also lower the recorded resolution as well.

I usually record 352x480 (a legal half-D1 resolution for DVD authoring) at 4Mbps and recordings are more like 2GB/hr. It's still big but that's why God made 400GB hard drives. :)
Author:  NTolerance [ Wed Oct 11, 2006 12:23 pm ]
Post subject: 
Is there any noticeable difference between 480x480 and 352x480 during playback on an SDTV?
Author:  ceenvee703 [ Wed Oct 11, 2006 12:46 pm ]
Post subject: 
I would argue that there is no noticeable difference, and certainly not while it's playing at 29.97fps.

I searched around and found this page (Television and Video Resolution) that certainly sounds authoritative:

http://members.aol.com/ajaynejr/vidres.htm

It states "the most resolution that will be seen for received [analog NTSC] TV broadcasts is 330 lines" of horizontal resolution.
Author:  baishen78 [ Wed Oct 11, 2006 12:55 pm ]
Post subject: 
Speaking of resolutions, why would you use 480x480 for a 4:3 broadcast?
Author:  ceenvee703 [ Wed Oct 11, 2006 1:37 pm ]
Post subject: 
A few sources (including the MythTV docs) say that 480x480 is a standard SVCD resolution.

http://www.mythtv.org/docs/mythtv-HOWTO ... esolution_

http://forum.videohelp.com/viewtopic.php?t=94382

As long as it's a standard resolution, a playback device will be able to compensate. So if you take a 4:3 image and record it at 320x480 or 480x480 or 720x480, as long as the playback device knows to take that resolution and stretch/squeeze it back to 4:3 for playback, it should appear correct.
Author:  andysl [ Wed Oct 11, 2006 7:21 pm ]
Post subject: 
i havent actually set this up yet, but it may be helpfull:
[url]http://knoppmythwiki.org/index.php?page=XviDEncoding[/url]

Can anyone tell me roughly what size a 1hour recording would be in XviD?


*edit: why wont my link work??

*edit:
stumbled across this link to answer my own question:
[url]http://www.linuxjournal.com/article/8524[/url]
Author:  ceenvee703 [ Thu Oct 12, 2006 5:32 am ]
Post subject: 
"Can anyone tell me roughly what size a 1hour recording would be in XviD?"

The size of any one-hour recording, whether Xvid or MPEG2 or MPEG4 or whatever, is entirely dependent on the bitrate you use to encode your material.

A 4Mbps video bitrate results in about a 2GB file for an hour program, as mentioned above. Halve that bitrate and you get 1GB for an hour program. Halve it again to 1Mbps (approximately the default bitrate for nuvexport's Xvid transcoding) and you get a 500MB hour-long file. If you recorded MPEG2 at 1Mbps, you'd also get a 500MB file, but since it's less efficient, it would look quite bad.

(Compressed audio is usually a tiny fraction of the file size, but of course as you use lower and lower video bitrates, it does start becoming a more significant fraction.)
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