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problems encoding an exact avi file size

Discussion in 'DivX / XviD' started by kmart, Jul 9, 2002.

  1. kmart

    kmart Member

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    I originally posted this on the DVD ripping board, before I realized it didn't belong there. I apologize.

    I have one DVD, and I've been practicing on it for nearly a week now, and I can't seem to get it right. Once I figure out what I'm doing, I figure I'll subscribe to netflix and try to rip 3 - 4 movies a week.

    Using the afterdawn 16:9 guide, I finally ripped and encoded a very nice and very watchable version of gattaca last night. I have no complaints about the quality. The movie is 1h 46m 25s long, and the audio quality is a 160 kbps mp3. In DVTool, I set it that the file size should be 1350 MB, so it could easily fit on 2 CDs. After cropping, the resolution is 640x272. According to DVTool, if I want a file of that size with those parameters, I should encode it at approximately 1570 kbps (I forget exactly what the number was).

    Thing is, when I woke up this morning and came to check it, the file was 767 MB, which is too big for a single CD. Now the fact is, this is the best looking divx rip I've ever seen, and I'm very happy with the results, so you might ask why I want it to be 1350 MB. Well, it's too big for 1 CD, so I might as well use 2 full CDs to store it, and get better visual quality, instead of using 2 nearly half empty CDs.

    I checked the numbers myself. 1570 kbps * 107 min * 60 sec/min * 1 byte/8 bits = 1.25 gigabytes, and with the ~125 MB sound file, it should be under 1400 MB to fit onto two CDs.

    So I set the bitrate to what DVTool told me it should be, I checked the numbers, and DVTool seems right...so why is the resulting avi file only 767 MB?

    Any help will be appreciated.

    BTW, here are the details, in case any of it's important:

    I used Smart Ripper to rip the DVD, DVD2AVI as a frame server, VFAPI Convert, to convert the .d2v into a pseudo-avi, CDex to convert the wav into a "wav-wrapped mp3 file" with the Lame encoder, then finally, I used Virtual Dub to encode the video with divx 5, in two passes. When I played it in DVD2AVI (the ripped .vob files) for the first few frames it said the video was interlaced, but after that it said progressive. Despite the fact that it said progressive, I added a deinterlace filter anyway, because when I looked at the video in virtual dub, the frames looked interlaced (when looking at a single frame during motion, it's pretty obvious when it's interlaced). Other than adding the deinterlace filter (blend frames) I followed the afterdawn 16:9 guide word for word.
     
    Last edited: Jul 9, 2002
  2. DoctorB

    DoctorB Guest

    Bit rate Calculaters are not exact. When encoding it does not use the same bitrate through out the movie because some seens requirer a higher bit rate or a lower bit rate. The bit rate given is the average of the movie. May be try a different bit rate calculator some may be better than others
     
  3. kmart

    kmart Member

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    Bitrate calculators might not give the right answer because of variable bitrates, but a bitrate calculator is a very simple thing, and all bitrate calculators will give the same result. 200kB/s * 10 secs = 2000 kB. All calculators will tell you the same thing. They just calculate the numbers, it doesn't matter what coded you're using.

    That being said, DivX 5 apparently only goes up to a certain bitrate. If it determines that using a higher bitrate won't increase video quality, it won't go above that bitrate.
     

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