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800MG onto 700MG CD - How ?

Discussion in 'MPEG-1 and MPEG-2 encoding (AVI to DVD)' started by swog, Oct 26, 2004.

  1. swog

    swog Member

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    I've recently obtained a movie in avi format that is almost 800MG in size and lasting 88mins.I'm now in a hurry to save this as my HDD is ready to die.

    If I wanted just to save the avi to copy back to my new HDD, would the method be different from a copy that could play back thru a stand alone DVD player.

    Could you explain the methods to 'shrink' it onto my 700MG 74min CD's.

    Thanks, swog.
     
  2. aldaco12

    aldaco12 Active member

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    First, a 700 MB CD NOT a 74' CD! (which would be 650 MB). 700 MB CD = 80' CD.
    Second, the 'true' CD capacity is measured in SECTORS not in size or length.
    The 'true' dimension is 80' CD = 360,000 sectors. 74' CD = 330,000 sectors.
    Depending on what you burn into a CD, those sectors can contain 2048 bytes (Data), 2336 bytes (movies), 2352 bytes (Audio OR RAW images, like ISOs or BINs). Tha remaining secors are occupied by EDC and ECC (Error Detection and Correction Codes, which are big for data, zero for sound and RAW images and few - 16 bytes - for movies).
    The 'size' is always expressed in Data, this means that 360,000 sectors = 360,000 x 2048 bytes/sector = 737,280,000 bytes = 720 Kb = 703.12 MB . Therefore it often said (wrongly) 'a 80' CD is 700 MB'.
    Into a "80' CD", that is a CD with 360,000 sectors, you can fit 360,000 * 2352 = 846,720,000 bytes of RAW data (Audio or images) or 840,960,000 bytes (360,000 * 2336) of movies.
    Therefore, into a "80' CD" you can fit about 836,000,000 bytes of MPEG Video-CD (because the VCD image takes some room - 10,600,000 bytes - a little more than the .MPEG but the 'image' can be up to 846,720,000 bytes).
    Finally, a 836,000,000 bytes MPEG is a movie about 83'30" long. The problem is that you said "an .AVI 88 minutes". The .AVI is NOT a Video-CD file, but a com├Ępressed movie (using some codec: DivX, Xvid and so on) and you can fit up to 2hrs of movie in 1 GB of room or 60' of movie in 400 MB (maybe losing some quality of the video)! The 'rule of thumb' is "you can fit max 83' of movie into 1 CD". Unless you can burn a 90' CD in your recorder, or you can overburn some bytes (bur you need a good burner for that), you have to split the movie into 2 CD (as I explained in my "100% working method to make a VCD" 'sticky' thread'.
    If you accept to 'lose' some video quality, maybe you can re-compress the original .AVI with DivX into a smaller size .AVI, using a smaller bitrate than the original movie (find the correct bitrate to use with the "DivX bitrate calcullator" and don't use DivX multipass but DivX 1pass.

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    Last edited: Oct 26, 2004
  3. swog

    swog Member

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    Thanks Aldaco, for your reply, very informative and though it didn't all make sense i'm gradually getting my head around it.
    What confused me was the fact that I downloaded a avi that was 700mb I then dragged it to Nero to burn as a VCD on 700mb disc, it didn't fit almost 800mb long.If I follow you correctly its due to the amount of data the different sectors can contain.

    Thanks Swog
     

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