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  1. i'm using avidemux v2.6.8 (Windows 7, 64bit) but i've noticed the same issue with other versions, including 2.6.10. I really like the program & it's great for cutting video but i've recently noticed that when i cut a video, avidemux will, depending on the source resolution, slightly change the display aspect ratio.

    For example, if a source is 960x544 the input AR & display AR show up (in media players like kmplayer & potplayer) as follows:

    1.76:1 & 1.78:1

    But, if i then use avidemux to cut a piece of that same video (note: i don't need avidemux to encode video, just cut), i get this:

    the display AR gets changed to 1.76:1

    for some reason, when cutting, avidemux matches the display AR to the input AR. Not a problem where, depending on the resolution, the two are the same.

    What i wanted to know was:

    - is there a way to avoid this when using avidemux? and
    - does it really matter if avidemux slightly changes the output AR? as long as the resolution is the same, will the 'cut' version look any different in practice?

    Thanks in advance for your help
    Last edited by Jason425; 16th Jul 2015 at 15:28.
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  2. Avidemux doesn't seem to keep the aspect ratio information when you're just copying the video (I'm assuming you're copying), but it makes it hard to know for sure what's happening as the aspect ratios being displayed in your screenshots are no doubt being rounded up and/or down to 1.76 and 1.78.
    960/544 = 1.7647

    Here's what a 960x544 video with a 1.76 aspect ratio looks like when opened with MPC-HC and after using the File/Properties menu (I just made one for testing, so it'll probably be different to the video in your screenshot):

    Click image for larger version

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    The bottom aspect ratio is the actual aspect ratio (as it's written to the container and only displayed if it's different to the resolution) and the top aspect ratio is the display aspect ratio. The two are virtually the same but the top one is rounded to the nearest whole pixel as it's how the video needs to be displayed (I'm pretty sure that's how it works). ie
    544x192/109 = 958.239
    544x479/272 = 958

    After remuxing with Avidemux, the aspect ratio info is gone.
    Click image for larger version

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    If the output file is MKV it's easy enough to fix. Open the original file with MKVMergeGUI and check under the format specific options tab. My 960x544, 1.76 aspect ratio MKV looks like this:

    Click image for larger version

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    Same aspect ratio as above, different way of expressing it.
    544x960/545 = 958.239

    Make note of the display dimensions, open the MKV saved by Avidemux, add the correct dimensions, then save that as a new MKV and you should be back where you started, aspect ratio-wise.
    It appears the aspect ratio written to the video stream remains intact when Avidemux remuxes, but not the aspect ratio written to the container (normally they'd be the same but the players probably look for the container aspect ratio).

    For other file types you'd need to use a different muxer but the principle would be the same. I don't know if you can tell Avidemux to keep the container aspect ratio, but that should help you to find a place to start looking, at least.
    If you're re-encoding and not just copying, I'm not sure what Avidemux does as I've hardly used it.

    PS. You can use MKVMergeGUI for cutting/splitting/joining MKVs but it doesn't have a preview. It'll keep the aspect ratio intact though.

    PPS. I think the latest MKVMergeGUI has had a revamp so it'll look different. I'm using an older version here as it's the last version to support XP. Sigh.....
    Last edited by hello_hello; 17th Jul 2015 at 09:22.
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  3. Thanks very much for taking the time to put that together - very helpful/useful

    Originally Posted by hello_hello View Post
    Avidemux doesn't seem to keep the aspect ratio information when you're just copying the video (I'm assuming you're copying)
    Correct, when i cut with avidemux i'm just copying; i use megui for encoding. Out of habit i've been encoding into an mp4 container but encoding into an mkv container isn't a problem. Alternatively, i can switch to 960x540 when encoding at that sort of resolution. The input/display aspect ratio for that is identical - 1.78:1 /1.78:1, so cutting that with avidemux doesn't cause that issue.

    Alternatively, i also tried boilsoft video splitter which doesn't have the problem avidemux does (aspect ratio info of the cut movie is the same as the source). A shame because avidemux is easier/quicker to edit files with than boilsoft, which has a small display window.

    ps - was wondering, does it matter in practice that avidemux doesn't keep the AR info/makes a small change? what i mean is, is it visible when watching the 'cut' version of the movie? I honestly can't tell when it's a widescreen source (16:9) - it's a very small difference - & only noticed this issue when i cut a 720x480 (4:3) mp4 file - the 'cut' video picture looked noticeably wider.

    pps, i'm also using mkvmerge 7.8; i've got used to it & didn't like the look/feel of the more recent version. Yes, a shame it doesn't have a preview window when it comes to editing mkv's.

    Thanks again
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  4. Are you cutting the video you're encoding, or cutting the encoded video?

    Are you aware MeGUI has an AVS Cutter under the tools menu? Save a script, open it with the AVS Cutter, add your edits, then save the "cuts" to the script. That way you'll only be encoding the parts you want to keep, and you don't need to edit on keyframes.
    The AVS cutter can also save a "cuts file" for loading into the audio section so it can be re-encoded to match the video. Or there's the audio cutter under the tools menu. It'll use the cuts file to edit the audio and rejoin the bits etc without re-encoding it, if you don't want to re-encode the audio.

    If the aspect ratio is very close to the resolution then it shouldn't matter if it's removed. It'd only change the display aspect ratio by a pixel or two. Obviously though if the aspect ratio and resolution are very different, it'd be much better to keep it.

    I convert PAL DVDs to 960x540 quite a bit myself. I'm a bit OCD when it comes to aspect ratios and if it's almost 16:9, I tend to adjust the cropping/resizing until it's exactly 16:9. I don't use anamorphic encoding myself because a player in this house ignores aspect ratios in MKVs.

    It's odd AviDemux doesn't keep the aspect ratio. When I checked after opening a file it showed aspect ratio "unknown" but displayed a pixel aspect ratio anyway. Maybe it's confused.

    Video To Video Converter has a "commercial remover" under the tools menu you could try. I didn't have a lot of luck with MKV in respect to aspect ratio. After editing a file and selecting the "direct stream copy" conversion preset the aspect ratio was lost. When I tried again by selecting the MKV conversion preset and "copy" for both the audio and video (the end result should be the same), it seemed to correctly add the aspect ratio to the commandline, only it wouldn't create the new MKVs and I didn't understand why it was resulting in an error. Sigh.....
    You might have more luck editing MP4s though. I didn't try those.
    Last edited by hello_hello; 18th Jul 2015 at 09:18.
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