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View Full Version : Question about method for capturing to XviD on-the-fly


FlimsyFeet
23rd October 2006, 14:27
So Strictly Come Dancing and The X Factor are on at the same time on different channels, and my wife wants to record them both. In the past we've recorded one on a DVD recorder and one onto VHS, but it's a bit of a hassle moving the VCR around as it normally lives upstairs. Since we have a Divx player downstairs, I thought it might be a good idea, instaed of using VHS tapes, to capture one programme with VirtualDub on the PC and encode to XviD on the fly, so it can simply be dropped as an AVI file onto data DVD+RW and watched with the minimum of effort.

I set up XviD with settings in http://forum.doom9.org/showthread.php?p=864376&posted=1#post864376. Using a target quantizer of 16 I ended up with a video bitrate of about 1200kbps - fine.

I used the lame acm codec for the audio, recording to 128kbps CBR stero 48kHz.

CPU is Athlon 64 X2 4200+. I was getting 50-70% cpu usage, and no dropped frames during capture.

One problem - the audio ended up way out of sync. I think I used the same capture timing options that normally work fine for analogue capture, so is this something to do with the MP3 encodign?

Second question, can I make things look nicer and encode more efficiently by deinterlacing and resizing on-the-fly as well? If so, what would be a recommended way of doing this?

DrP
23rd October 2006, 17:18
FlimsyFeet, from the sounds of it you are in the UK. If that's true, do you have access to freeview? You'd do a much better job of it all round if you can record digital TV directly with a couple of DVB-t tuners.

FlimsyFeet
23rd October 2006, 20:16
No freeview is not available in our area. And even if it was, I think we'd have to pay 200 for a new aerial.

setarip_old
24th October 2006, 00:29
Hi!so is this something to do with the MP3 encodign?That is VERY likely. Standard operating procedure for capturing is to capture audio as Uncompressed PCM (.WAV) and compress to .MP3 afterwards.

I'm (pleasantly) surprised to hear that capturing in XvID (rather than the "standard" of using a lossless codec, such as HuffyUV) hasn't resulted in dropped frames for you...

FlimsyFeet
24th October 2006, 09:14
I'll try capturing with uncompressed PCM, and see if the sync problem goes away.

I'm not sure if my standalone will like PCM inside an AVI file (the overall bitrate might be too high), but it's not a big step to re-encode the audio and direct stream copy the video to a new file.

Regarding the second question, I've found that the help file included with VirtualDub is much more helpful than the documentation on the web site:
Filters / Enable RGB Filtering
Pushes video through the normal VirtualDub video processing filter chain. Nearly all video filters can be used here; however, the temporal smoother should be avoided as it has a frame lag, which is not supported in capture mode.

Using normal video filters will force the video to be converted to 32-bit RGB, and consumes a significant amount of CPU power.

So I might be able to do a blend deinterlace and bilinear resize, depends on the CPU.

setarip_old
25th October 2006, 02:48
I'm not sure if my standalone will like PCM inside an AVI filePlease re-read my suggestion,capture audio as Uncompressed PCM (.WAV) and compress to .MP3 afterwards.

FlimsyFeet
25th October 2006, 09:08
Please re-read my suggestion,.Please re-read my original post!
...so it can simply be dropped as an AVI file onto data DVD+RW and watched with the minimum of effort.:p

jggimi
25th October 2006, 15:51
Before this gets any uglier, I need to step in.

That's enough, fellas.

Flimsy, it is likely your player handles Linear PCM audio just fine. But you won't know until you actually try it.

But, Flimsy, as you said:...it's not a big step to re-encode the audio and direct stream copy the video to a new file.So the entire argument is specious, on both sides. Any further urination will result in thread closure and official warnings (strikes) for bad behavior.

Surf
25th October 2006, 18:48
Filmsy, I have been using AC3 codec 192/48k without problem but capturing using VirtualVCR, not VDub which is the next attempt. There is the audio setting in VDub which you may need to fidget around....

One thing though, I don't understand why are you choosing such a low quantizer? Are you not "Watch n Erase" with the tv recording? Heavy compression may mean taxing the cpu(I think). Right now I am using setting #2. The two hour taping resulted in over 5gigs. Chopped the commercials out and the file will be small enough to fit a RW disk nicely.

It's "stunning" when up-converted to 1080i.