Reducing resolution (all else same)

Discussion in 'DivX / XviD' started by anodized, Jun 26, 2006.

  1. anodized

    anodized Member

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    I've dibble-dabbled in video editing before, but I usually screw it up. Anyway, I have 12 video files, most are 350mb, but 3 of them are 715mb. The three that are 715mb have a resolution of 960x544. I'd like to reduce the resolution to somewhere around 608x344. I'd like to keep the same audio (ac3), but I have no idea how to go about doing this. Gspot says that the file is XviD (yeah, real descriptive). I would really appreciate someone helping me out on this. Please treat me as if I'm stupid, because I don't know much about this at all. Feel free to flame me if I'm in the wrong forum! Thanks.


    --anodized.
     
  2. SOCOMII

    SOCOMII Regular member

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    Well get AutoGK and load up the files then under "advanced options" go to resolution and pick 608 (but i would pick 624) and it will automatically pick the vertical resolution for you dpending on your video format, which im guessing is 16:9. then under audio go to original and for the codec pick XviD. You can selct the targed size also or the quality. if these are 40min files, i would suggest atleast over 350mb, since the audio is ac3. Then add it to the batch mode and you can add all 12 of your files and leave it to convert overnight or whenver.
    GooD Luck
     
  3. aldaco12

    aldaco12 Active member

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    The movie seems to be a 16:9 movie to me, since:
    16*60 = 960
    9*60 = 540 (not exactly 544, but very similar).

    If you want to reduce its resolution but keeping the same Xvid effectiveness, choose a resolution so that:

    New_resolution / 960*544 = New_size/715 MB. For instance, if you want to create a 350 MB file, New_resolution = 350/715 * (960*544) = 255642 pixels.
    The resolution 672x380 is very close to that number (Y is not exactly 672/960*544 since it would be 380,8, I know that DivX has the limitation Y being divisible by 2 (Xvid hasn't them, but I wouldn't like to see a 672x381 movie. I don't think you'll manage to detect a variation in the aspect ratio of the magnitude of 0.2% [0,8/380]).

    Therefore, if you want to make a 350 MB AVI giving the same 'effort' to the codec, you can choose up to 672x380.

    For the size, just use VirtualDub's bitrate calulator (Video__Compression__Xvid__bitrate calculator) inserting it the target size, the audio's bitrate (384 more likely or, seldom, 448 kbps) and the movie's length.

    Ah, to keep the same audio, use VirtualDub(Mod) to change the video (Video___Filters__Add --> Resize. Set the Resize windth/length and use "Lanczos3" as filter (you could also use 'precise bicubic' but I prefere Lanczos3). By default, VirtualDub "direct stream copies" the audio, so it'll keep AC3.
     
    Last edited: Jun 27, 2006
  4. anodized

    anodized Member

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    Alright, I see what you guys are saying. Thank you very much for the replies. Since I've used virtualdub before, I tried that method and failed (heh) because there were tons of settings that I don't know shit about and the projected file size was around 670mb (I let it go for a while). I figured I'd give autogk a try... It had an error installing the xvid codec (xvid.ax couldn't be opened for writing, I said ignore..), but after install I followed the directions and it's processing now. I'll let you guys know how it turns out. Thanks so much for the replies.
     
  5. anodized

    anodized Member

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    It worked with AutoGK. Hmm, I love you guys. Thanks so much, you don't know how long I've wanted to figure this out.
     
  6. SOCOMII

    SOCOMII Regular member

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    glad to see you got it working =)
     

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