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Analogue video capture

Discussion in 'Desktop & Laptop Computers Forum' started by Darren Blake, Dec 16, 2003.

  1. Darren Blake

    Darren Blake
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    I was trying to capture a ten minute (approx 4Gb) segment of video from a VHS recorder last night to encode it onto a VCD. Almost got it to work but hit a small snag.

    Bear with me as I cannot remember the exact resolutions, but my capture card drivers come with several preset resolutions for the captured video. The one I wanted to use was the same as PAL VCD. There was also a setting "one below" this which seemed to be the closest res which used nice round numbers.

    My problem is that I want to capture at at least 25fps. If I used the "one below" res then I could do this easliy. However, if I changed to the PAL res setting, the framrate dropped to a measly 10/12fps. what the fudge????

    My setup is as follows:
    PC: 1.7GHz processor, 256Mb DDR RAM.
    Capture card: Pinnacle systems, capturing through composite.
    Cature target disk: 80Gb 7200rpm 2Mb cache.

    Why, just by tweaking the res up slightly, does the framerate drop by 50%?

    TIA.
     
  2. Magsy

    Magsy
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    What software are you using? Capture to mpeg1 I assume?

    With a cheap pb-tv100 from pcworld, using Mainconcept mpeg encoder on a p4 2.6 I can do realtime mpeg2 @ 720x576 (D1 - full pal) at any bitrate. So I'd guestimate yours should be fine with a quarter of the information in mpeg1.

    Pal vcd should be something like 352x288 mpeg1 @ 1150kbps.

    Could well be its changed more than just the resolution, maybe its upped the quality of encode (usually just a small slider) which can make a huge difference. (speed vs quality tradeoff)
     
  3. Darren Blake

    Darren Blake
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    Capture is to AVI. No recompression. Res is just under 352x288 (can't recall the exact value). Software is Vidcon32 through a Pinnacle PCTV analogue card.

    Someone else has told me that the amount of data being passed to the disk may be more of a limitation, hence compressing on the fly may yield a better framerate. I had assumed that the less processing the machine had to do in real time the better.

    Will experiment tonight.

    Cheers for the reply!
     
  4. Darren Blake

    Darren Blake
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    FIXED! :D

    Data throughput was the problem. Indeo compression set at 85% quality lets me grab at 352x288 res at 25fps.

    Sorted. Cheers!
     
  5. Magsy

    Magsy
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    Urgh, if that HD cant do quarter pal uncompressed you have a problem!!
    I have run of the mill 7,200rpm drives and they will quite happily do full pal.

    Surely indeo is ruining the quality? Quite an old codec.

    Try using huffy yuv , its highly regarded as the best lossless codec. Effectivley retaining the uncompressed PQ but at a lower data rate (not much but enuff) This should then turn quite nicely into VCD.
     
  6. Darren Blake

    Darren Blake
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    I'm fairly happy with the quailtiy of the capture, but I've yet to do one "in anger" and turn it into a VCD.

    Could you give me a rundown of your hardware / software? I can't make out whwther you are using a hardware MPEG-2 encoder or not. There's no way my machine could do real time MPEG 1 let alone MPEG 2, so I guess you must be using hardware?

    The people who told me it may be data throughput to the disk were the support forum operators at Puremotion (who's video editing software I use).
     
  7. Line_Man

    Line_Man
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    I think MPEG 2 is SVCD
     
  8. Magsy

    Magsy
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    You can do realtime Mpeg 2 on a resonable machine, obviously the faster it is the higher quality you tend to get. Mpeg1 realtime is no prob at all. I used a P3 733 at my GF's house to do realtime SVCD for ages (PVR), I then stuck a 1ghz P3 in and it wud just about do 720x576 mpeg2. This was with Cyberlink Power VCR II.

    I have nothing special, the much talked about cheapo pc world capture card and a P4 2.6 with 2 60gb drives (no raid..) I'm using Mainconcept Mpeg Encoder though, it costs good money unless you can 'aquire' it somehow :p

    Disk throughput could be the issue, but what I'm trying to say is that you shouldn't suffer it at such a low rate. Try huffy if you arent happy with the quality!
     
  9. Darren Blake

    Darren Blake
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    Can you tell me a bit more about your capture card please? Just to be 110% sure, you are talking about analogue capture aren't you? Not DV?
     
  10. Magsy

    Magsy
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    Yea, analogue via svid from sky+
     

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