what bitrate should i use to record live tv?

[bradlewa]

I'm fairly new to this whole PVR on your computer thing. I have a Hauppauge PVR-150, which I generally use to record TV shows. I've been recording at the preset DVD Extra Long Play (2.5MBit/sec), but I'm not sure if I'm over-encoding. I know with music it's always dumb to try to (re)encode something that's already, say at 128 kbps to a higher bitrate. I guess my question is, what quality or bitrate is live TV? What bitrate would I use to make an exact copy? And how low of a bitrate do people generally encode without losing much quality?

Any help with this is greatly appreciated.

BB

[greymalkin]

if we are speaking of analog sources then "bitrate" and "resolution" are not applicable. If you were to try and make them applicable..you would probably have to say bitrate: infinite and resolution: infiinite.

okay..enough badgering...most people don't see a difference when they record tv/vhs @ 352 x 480 @ about 4 to 5000kpbs

[presto]

record tv/vhs @ 352 x 480 @ about 4 to 5000kpbs

I have the same card and the above is correct for good quality. However I have my Beyond TV set for 352X480 @ 2400kpbs for ordinary everyday acceptable quality. It let's me fit a lot more on my hard drive.

[Noahtuck]

okay..enough badgering...most people don't see a difference when they record tv/vhs @ 352 x 480 @ about 4 to 5000kpbs

Wow!!!!!!
If i record something off of TV and do it in 352X480 and 720x480, i can see a huge diff.!!!!!!!!!!
I must fall way out of the range of most people 8)

[bradlewa]

Thanks for the responses. So, I've seen a couple of charts on digitalfaq.com and mediachance.com that say if you want to record at 720x480 you need to increase your bitrate to ~6000-8000 kbps in order to get a good recording, whereas using 352x480, you only need ~2500-4000 kbps. Is this really true? I mean, because I've recorded TV at 720x480 at a VBR of 3000 kbps and a max of 4400, and I really don't see a difference (at least on my computer screen) between this and a 352x480 recording at the same bitrate. In theory, even though they should be the same filesize, wouldn't the higher resolution be the better quality recording?

[davideck]

In theory, even though they should be the same filesize, wouldn't the higher resolution be the better quality recording?

Indeed, I find this to be true for my PVR-250.
I always capture at 720x480.
720x480 at 4500 kbps looks great for 2 hour DVDs.

[syeager]

Are you using your noise filter on your captures? I have a different card, an ATI TV Wonder Pro, and if I use a noise filter during capture, the bit rate is apparently calculated before filtering. If not, during noisy broadcast or for fast action, like sports, an even higher bitrate is required. I experimented once with a 250 and found that there was a marked improvement capturing at 704x480 over 352x480, even with the bitrate set to 8mb for both. Also, for sports, I found that capturing at the maximum 12mb also showed a dramatic improvement in quality.

It also depends upon whether you intend to burn to dvd or just watch it later and delete it. I like to capture at pretty much max quality and rerender to proper dvd specs if I am keeping it.

[greymalkin]

okay..enough badgering...most people don't see a difference when they record tv/vhs @ 352 x 480 @ about 4 to 5000kpbs

Wow!!!!!!
If i record something off of TV and do it in 352X480 and 720x480, i can see a huge diff.!!!!!!!!!!
I must fall way out of the range of most people 8)

is that that new thing called sarcasm??? :P

yes you are different and strange. all of your friends can't see the difference and they snicker at you behind your back.

seriously, though..are you recording from vhs/analog cable? I have heard some people say they notice a difference when capturing at 720x480 resolution, but not a HUGE difference and there is a point of diminishing returns where the ratio of quality to space on the dvd skews into a tangent...

[Noahtuck]

is that that new thing called sarcasm??? :P

But seriously, no, i was serious

yes you are different and strange. all of your friends can't see the difference and they snicker at you behind your back.

Behind my back hell!!!!!! They have no problem telling me to my face :P

I have had so many people say they can't tell any diff. watching the 2 before i went to just dvd resolution years ago when i bought my first dvd burner and they say it to my face and i laugh at them :P
Would say, that was a vcd you just watched and they would go huh... never would have known blind MOFO's!! 8)
Have this one friend who like's to... ummm... torrent, and she had this video, converted it and brought it over to watch, the first minute i was like damn!!! i was seeing all kinds of shit through the whole thing!!! and she was like, it looked as good as any dvd i have seen i was like damn!!! that baby would have went right into the scrap pile

seriously, though..are you recording from vhs/analog cable? I have heard some people say they notice a difference when capturing at 720x480 resolution, but not a HUGE difference and there is a point of diminishing returns where the ratio of quality to space on the dvd skews into a tangent...

Well, even from over the air broadcast's if i capture/record at full dvd spec's or anything lower & vcd/svcd i can tell the diff in a second watching it on my 27" and watch it in the living room on the 54" and you would have to be seriously blind not to see the diff. right off
But even back before dvd burner's i was always a stickler for the best possible video quality. Other lower resolutions are acceptable to me for viewing, but i can definatley see a diff. right away watching them.

[slacker]

I can also vouch for the fact that when using Vegas (MainConcept encoder) 2 pass vbr 704x480 looks WAY WAY WAY better than 352x480 at the same bitrate, for example 4mbps. I can't imagine using 352x480 for anything!

[edDV]

For a full quality NTSC TV signal 704* will get superior results to 352 on the frist pass. Analog PAL is usually broadcast with wider analog bandwith so the differences would be even greater.

Depending on the capture card technology, 704 can look significantly better. Bad cards will cap 640x480 and rescale with poor filters to 704 or 352.

Good cards will oversample, thus reducing the spec required for the analog low pass anti-alias filter, to a 704x480 raster. Realtime hardware encoding cards can then process with full data and then filter for output at either 704 or 352x480. 704 should still look better but 352 will look good although with somewhat less luminance high frequency detail.

Software encoders can do the same thing as a second non-realtime process.

NTSC VHS has luminancce cut below 3MHz. Broadcast NTSC has 4.2MHz luminance bandwidth. Laserdisc, Hi8 and S-VHS can have up to 5 MHz.

352x480 implies an equivalent analog luminance bandwidth around 3.38 MHz. That would imply some loss of detail for all but VHS.

The tradeoff is some detail for half the bitrate.

Digital cable/dbs SD channels are usually transmitted as 3-7Mb/s MPeg2 ~530x480 to the set top box.



* 720 is 704 with 8 extra padding pixels on the left and right. 704/2 = 352

[SatStorm]

I prefer 704 x 576 when I capture analogue TV, using an average of 4000 kb/s. There are some blocks once here and there, but overall the picture is OK