AIW980Pro: Confused About Different Sized Captures

[Tom Saurus]

I use an AIW9800Pro to capture video with. At times when my hard drive is nearly full it captures the video with good quality, and smaller file sizes. For example a got something captured the other week and it got it as 3.6Gb and the show was 1 hour and 50 minutes and my hard drive was nearly full. I cleared up some space and the capture card seemed to take that as permission to capture the file bigger. I got 4.5 GB for an hour and 40 minute show.

Here are my settings:

Mpeg2DVD
720x480
8.0 mb/s Max Bit Rate
6.0 mb/s Target Bit Rate
Motion Quality 99
4800 khz 16 Bit Stereo
256 kb/s Audio

I only ask this question because it is nice to get an entire show on one DVD at times, instead of having to split it up over two dvds. I use the vbr instead of the cbr. I wonder about this because sometimes when I have alot of hard drive space free it is as if the capture card senses this and decides a bigger file is just what is needed.

There doesn't seem to be that much difference in quality between the bigger and the smaller files. These captures don't turn out as sharp as what Hollywood does, but it turns out pretty decent for our liking. Most of the time I am recording using the S-Video.

[Nelson37]

Filesize on ATI caps is somewhat variable, brighter action movies seem to get larger while darker, slower flicks will be smaller.

Also, capture settings will sometimes change themselves from VBR to CBR, on one version on MMC the Motion setting would reduce by one each time you looked at the settings.

Double-check to make sure all settings remain unchanged.

I have never noted any relationship between space available and capture file size, though I haven't really looked for it.

What version of MMC are you using?

[Bodyslide]

Tom take a look here
http://digitalfaq.com/

Lordsmurf has alot of info on the ATI cards.

[Tom Saurus]

Nelson37: I am using MMC 8.50, I am hesitant to upgrade to a higher MMC because I really don't understand completly how to do that, and this seems to be working fine for the most part. The Settings seems to stay the same.

[lordsmurf]

Drop res, lower bitrate.

352x480 3.5Mb/s

[Tom Saurus]

lordsmurf: I went to 720x480 and the 6.0Mb/s because I have tried the way you recommended on your website and the resulting DVD's didn't look good on my tv or when I was extracting still pictures. Working with the 720x480 gives a much sharper picture.

It just confuses me to why at one time a show can be more compact, and at other times it is significantly bigger, even though the time frame is the same. For example 90 minutes can be too big to fit on a DVD, captured at a certain time, and at another it is a mere 2.8, 3.2, or 3.6Gb.

[Nelson37]

As a test, try capping several episodes of the same series, or even the identical episode or movie with different space available on your HD.

Are you using the TV-on-Demand feature?

As for Smurf's "advice", lowering the bitrate and res will not solve your variable size problem. It is also well known, to just about everybody but him, that ATI cards give better looking caps at 720, as you have noticed.

[Tom Saurus]

Nelson37: I have recorded all 32 Episodes of "Johnny Ringo" to watch until the series is released on DVD by Hollywood, then I will buy those. Most Episodes were 23 minutes long, except for the first two which were 25 minutes long. Well anyway, at first these episodes were around 900mb, and as my hard drive filled up, they went down to 800mb then 700mb then finally towards the end of the series they episodes were about 680mb. Back near the beginning of taping when I had more space available on the hard drive one of these episodes was 1.1 gb. For quite awhile now, I have only had 30 GB available.

I didn't notice much difference in quality, between the different sizes. Though I do think the bigger files you did notice a little better quality when getting still caps.

This difference in sizes confuses me. I am working on reclaiming my hard drive and offloading about 80 Gb's of shows to DVD.

I haven't tried the "TV on Demand" feature, since I don't have cable. I record from our Star Choice receiver via the S-Video and the jacks for the stereo sound. I have lately been trying the "Personal Video Recorder" feature and scheduling when the MMC turns on and records what is available to it from the S-Video Imput.

I notice that S-Video is very sharp, especially when it comes to colour. I don't want to upgrade MMC because I think ATI is going to follow in Microsoft's footsteps and start limiting what you can record with your Capture Card. I think it will get to the point, that one will not be able to use their capture cards to record TV, but only to capture Digital Video Camera footage.

But a factor in this is at times when it comes to recording TV Shows, I find I cannot cut the commercials acurratly when the show is airing so I let the computer record the whole show, commercials and all and take it to Womble Mpeg Video Wizard and then cut out the commercials and since it doesn't re-encode I find I don't loose any quality. The only problem with that is when you take this file into TmpgEnc DVD Author, you have to make sure you select the second frame as your starting point if you are cutting a video to split it between two DVD's, like puttting part one of an episode on one DVD and continue it onto another. The first frame doesn't cooperate, but is one frame, so it's presence is so insignificant it doesn't matter.

[lordsmurf]

Well, pick your poison.

Do you want to stuff lots of video on one disc?
Or do you want hi-res stills?

You cannot have both.

Or better yet, buy DL media and go that route.

720 caps will not look "better" unless the sources was also "better" .... meaning not tv, not VHS, etc. At any rate, 720 on an ATI is slightly aliased, use 704 because that's truer to the card. 352x is closest to most sources.

Also, try some specials screen image software.
There was one reported by BJ_M about a month ago, check the "news" forum for it.

[tluxon]

Here's my take on this.

The reason filesizes are different has to do with how easily frames can be compressed in real-time by the encoder. If B-frames and P-frames don't have many differences from the fully defined adjoining I-frames, an encoder can keep up quite easily and define all the differences fairly easily with good compression. From what I can tell, dark scenes often don't have as many motion detected areas in the frame which usually results in fairly high compression rates - thus smaller filesizes. Movies often fall into that category unless there's a lot of highly lit action. Sports are more brightly lit and have relatively high amounts of detectable motion, so compression is more difficult to achieve in real time - usually resulting in larger filesizes.

Consequently, I have often found 352 x 480 to be superior to 720 x 480 for low to moderate bitrates - especially for sports. As allowed bitrates get higher, the nod turns in favor of 720 x 480 because the needed compression is lower. A combination of a high bitrate and selecting only I-frames makes it even easier for the encoder to keep up, but of course creates larger files.

cheers,

Tim

[Tom Saurus]

tluxon: I think you are correct. I notice this bigger file size when a movie or tv show has alot of action in it; like when I tape pro wrestling tv shows. Thank you very much for your response to my querry. Also thank you to Nelson37 and lordsmurf for your contributions.