Questions on Aspect Ratios Handbrake and FFmpegX Also EXTRA TIME IN THE END

Discussion in 'Digital Video' started by MacRacer, Feb 6, 2012.

  1. MacRacer macrumors regular

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    #1
    Hello everyone. I have a question since I really don't know what I am doing and such. I have bought myself a 64 GB iPhone 4S and I want to take some of my Anime and Movies with me. WELL, I learnign and playing around. I notice that when I come accross the aspect ratio, for my 16/9 videos. The original size is like 720p, but when I choose a preset in Handbrake or FFmpegX, it will cut the height down to something sivided by 16. I want a low bit rate of 600-800 and a size width of 640. My questions is with the height. Most all the time, it will divide the video by 16 (from what I read) and I get a 640x352 video size. Is this normal with videos? If using a ratio of 16/9, should it be 640x360 instead of 640x352. FFmpegX doesn't have a way to change that aspect but I know Handbrake does. WIll it hurt the way the video looks with cutting the height down 8 pixels? I have anime series on DVD and well, I also downloaded it too. The source video is right at 640x360. But when I take it into handbrake, it will moves the size right back to 640x352. What should I do with the size in the end? I just so over my head with video size thing and I hope someone can explain it to me in simple terms.

    I also run into this error with Handbrake, a 24 minute video will end in 27-29 minutes. I get this extra 5-7 minutes of black video t the end of the video that weighs in at 30-50 Mb extra in data size. Is that just a bug in Handbrake or what. I working with DVD and MKV files.

    Thanks
     
  2. MacRacer thread starter macrumors regular

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  3. DisMyMac macrumors 65816

    DisMyMac

    Joined:
    Sep 30, 2009
    #3
    The presets are probably adjusting the Pixel Aspect Ratio (PAR) to make the video fit into the Display Aspect Ratio, no matter what resolution you choose. If you want to experiment, open any video in Handbrake, then click Picture Settings and change Anamorphic from to "None" to "Custom" and Cropping from "Automatic" to "Custom" (and of course click Preview to see what it does).

    Note that the i-Phone/Touch actually has a 1.5:1 screen, which isn't 16:9 (1.78:1). That doesn't mean much - it will simply display letterbox at the top and bottom of the screen, but it does make the conversion more complicated.

    I believe Handbrake automatically crops black edges, but ignores them if you select any preset. Don't change the presets too much if you want to make sure your iPhone can play it.

    In FFmpegX, you can adjust the video size to anything after selecting a preset. I don't think it crops automatically, and I don't know what effect "autocrop" has (maybe it will distort the video dimensions).

    If the video Display Aspect Ratio is 16:9, then the resolution can be 640x360 or 640x352 (or even 10x20) and only the PAR value will change. It's not cropping 8 pixels nor stretching/squishing the image so that people look funny (too thin or too fat). It's re-calculating every darn pixel to a new color value to make the new format resemble the original as closely as possible.

    Honestly, I hate dealing with PAR ratios (I feel they should ALWAYS be 1:1 in a perfect digital world), but luckily we usually don't have to worry because they are set automatically by the encoder. Especially with anime, it's very hard to notice distortions caused by reasonable changes in PAR values.
     
  4. floh macrumors 6502

    Joined:
    Nov 28, 2011
    Location:
    Stuttgart, Germany
    #4
    As for the resulting 352 pixels: For all mpeg4 codecs, including the probably used H.264, it is very advantageous to have pixel amounts that are dividable by 16 in both directions. 352 can be divided by 16, 360 can't. You will get better quality with 352 pixels (even though at first look it's a smaller number). It has to do with the compression and chroma subsampling of the codec. If you really want to know more, ask again. :)

    The aspect ratio in most videos is independent of the pixels, as the second poster has already explained. The pixels will in the end be stretched accordingly. As a matter of fact, your original DVD files will always have a size of 720x480 pixels (in the US) or 728x576 pixels (in Europe), which is far away from an aspect ratio of 16:9.
    I have never used ffmpegX, but I know ffmpeg (the command line tool) pretty well, and ffmpegX is just the GUI for that. So I am pretty sure you can adjust the aspect ratio, too. On the command line, it's simply "-aspect 16:9".

    I have no idea why handbrake would add some black content at the end. I have never had such a problem with the tool and have ripped several video DVDs with it. Sorry, can't help you there.

    If you want the best quality for your movies, I would recommend to not care about the pixel numbers you are presented with, but rather get a good encoder. I can assure you that Apple's Compressor will give you a much better result on your iPhone than ffmpegX or Handbrake. It will cost you 50 bucks, but the encoding is way better optimized, especially for iPhones and such.

    I'm starting to ramble. If this helped, fine. If you have more questions, shoot. It's daytime in Germany now and I might check more often than when you originally posted. :)
     
  5. MacRacer thread starter macrumors regular

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    #5
    DisMyMac & floh, I thank you for your input on this. I been playing around some more and what not. So the PAR jus stretches the image in the end. I video encoded to 640x352 is stretched back out to 640x360, in my case 626x352 which is shrunk. I do notice horizontal lines though, vary light lines, very noticeable in red colors. I think I will just use handbrake and turn the divided 16 number to 8 and go on from there. I think it looks more cleaner and the fine detail shows better. I end up downloading movies then go but the dvd later. So some movies and anime shows are in the MKV container and I don't think compressor will help me. I also don't have a DVD drive on my MBP, but I do rip them on my little HP computer and well, it takes forever. Thanks for the input, it does clear up what I am looking at in the settings a little bit more understanding of what I am doing in the end.
     

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