AVI to SVCD - Encoding increases file size? Wont fit on CD!

Discussion in 'MPEG-1 and MPEG-2 encoding (AVI to DVD)' started by j.lintern, Feb 8, 2003.

  1. j.lintern

    j.lintern Member

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    I have an AVI file which is 685 MB in size. Using GSpot I found out that its a Div3 codec, DivX 3 Low-Motion, 640 x 288 (2.222 : 1), 857 kb/s, 25fps, 01h 36m 58s.

    Can anyone explain why when I convert this to MPEG1 or MPEG2 using TMPGEnc the file size increases (to 900MB for MPEG1 - VCD or nearly 2GB to MPEG2 - SVCD) ??

    The quality is then worse then the original AVI video yet the file size is a great deal larger!! ??

    I thought the conversion is suppose to compress and reduce the file size with the comprimise of lower video quality ??

    Whats going on here!?

    So I now have the problem that when using NERO to burn the converted MPEG video to SVCD it will not fit!

    From my understanding, I have to convert the AVI file to MPEG 1 or 2 to create a SVCD to play in a DVD player. If this increase in file size is correct after converting in TMPGEnc, then how do I go about putting the large MPEG file onto several CD's ??

    I was hoping to use SVCD for the higher quality, but the file size seems to be ridiculously high at 2GB if I were to do this, meaning many CD's for a 1.5 hour film!

    Can anyone help and explain whats going on here?

     
    j.lintern, Feb 8, 2003
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  2. loaded

    loaded Moderator Staff Member

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    The size of SVCD MPEG and VCD MPEG is proportional tothe length of the movie. Approx 15MB per minute on SVCD and approx 10MB per minute on VCD, so the size of the file is based on the length of the movie (Yes you can decrease bitrates and stuff in mpeg2, but not is you want it to work as SVCD).

    And yes, the quality of a converted avi, which is already compressed into an Mpeg, which is another form of compression, will always lower the quality.

    Yes, you have found out the hard way, if you want SVCD or VCD you will have to use Mergre and Cut function in TMPGEnc to cut 2,3 or even 4 CD-R sized files and swap discs in your standalone!!

    Way out : Buy a DVD writer, sorry, but that is the only way.

    :)

    Paul.
     
    loaded, Feb 8, 2003
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  3. dRD

    dRD I hate titles Staff Member

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    VCD has a static bitrate of 1150kbps and therefor 74min CD holds exactly 74mins of VCD, whatever tricks you do. And as for SVCD, almost-DVD-quality can be achieved by putting 40-60mins of video per CD, so normal movie takes about 2 CDs.

    And re-encoding from already-encoded source, such as AVI to whatever other lossy format, will always weaken the quality -- same happens in all lossy conversions, whether it is AVI-2-VCD, SVCD-2-AVI, even AVI-2-DVD the AVI quality is better. And in DVD-2-AVI (provided the AVI means in this case DivX encoded AVI-wrapped video) obviously DVD is the one with better quality.

    You can demonstrate this by having a DivX that you encode to DivX again and then encode the resulting DivX to DivX again and then the resulting DivX to DivX again and... Eventually you will have 640x352 sized screen blinking white and black full screen colours every 10secs, nothing else.
     
    dRD, Feb 8, 2003
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  4. loaded

    loaded Moderator Staff Member

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    Heh dRD, just beat you to it!

    :)

    Paul.
     
    loaded, Feb 8, 2003
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  5. j.lintern

    j.lintern Member

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    Thanx for your replies but I'm still a bit confused.....sorry!

    I thought avi movies are 'raw data' i.e. not compressed? Which is why avi movies tend to be big files but better quality then mpg movies?

    I found this out when capturing some video using a TV capture card. The avi file was huge but when I converted to mpg it was smaller, though obviously poorer quality.

    I understand that compressing a format which is already compressed will lower the quality - this seems to be what you are saying I have done?

    But then why does the file size increase if the quality is lower?

    For example, if you convert a 24bit picture to a 16 colour picture the quality is obviously reduced but so is the file size.

    In the case of this movie I converted from avi to mpg (I presume this process compresses the movie?) the quality got worse, which you would expect, but the file size got bigger! Which doesn't make sense!

    So really I would be better off not compressing it to mpg because I lose quality (which you would expect) but it 'INCREASES' the file size! What is the point in that!

    Why have a large low quality movie when you can have a small high quality movie!?

    But I have to convert to mpg to play in a stand alone dvd player so I'm stuck.

    Anyway, how do I go about putting this movie onto 2 CD's using TMPGEnc then? I presume I have to create several MPG files no more than 700MB in size?

    And just out of interest, as I am using a laptop I was wondering if there are any reasonably priced 'external' DVD writers which anyone could recommend.

    Its a shame I can't use my new stand alone Philips DVD recorder!
     
    j.lintern, Feb 9, 2003
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  6. dRD

    dRD I hate titles Staff Member

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    AVI doesn't tell anything about the video. Nothing at all. AVI is a wrapper format, that describes how it is packaged, but doesn't tell what encoding algorithms it uses -- you can have even .avi that is encoded with MPEG-1 or MPEG-2 and be VCD compatible, but just have AVI wrapper.

    Your "huge AVIs" mean normally Huffyuv or MJPEG encoded AVIs. The AVIs you find from the Net in form of movies, are normally DivX or XviD encoded -- which both are MPEG-4 encoders. So, those AVI files you download from P2P networks, are MPEG-4 files.
     
    dRD, Feb 9, 2003
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  7. dRD

    dRD I hate titles Staff Member

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    I recommend you take a look at tool called DVD2SVCD, it can also convert AVIs to SVCDs or VCDs. Pretty complicated to use at first, but read through our DVD to VCD with DVD2SVCD guides from our article section and you get the idea of options in general, then just apply the ideas to AVI conversion instead of DVD conversion.
     
    dRD, Feb 9, 2003
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