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Thread: Lossless conversion 4:3 to 16:9?

  1. #1
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    Default Lossless conversion 4:3 to 16:9?

    Hi - I admit I am a newbie and have joined initially to ask this question but gere goes:-

    I have a Canon Camcorder (Std def) that has a pseudo 16:9 mode, meaning that if you play back the video on your TV direct from the camcorder you correctly see 16:9.
    But if you use a firewire cable and record the footage to a PC as an AVI file, every video player sees it as 4:3 an the image is obviouly squashed.

    So I need to
    1/ Convert the AVI file to 16:9 in a lossless way so I have a new master copy
    2/ And so I can burn a DVD that shows the correct aspect ratio.

    The one thing I do know is that there are all sorts of standards and formats in this game, may of which do not involve lossless conversions, also that much of teh software is hugely complex.

    What I am really after is a piece of freeware that opens the file, does the aspect ratio conversion and resaves - without lossy recompression

    I have done the conversion successfully using AVIRecomp - but I'm unsure if this has been a lossless operation?

    Many thanks!

  2. #2

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    I'm not a CODEC expert. (but that hasn't stopped me in the past from giving an opinion). I don't thing you have a 4:3 that needs converting to a 16:9, you probably have stretched pixels as opposed to square one which gives a 16:9 looking image on a TV because thats the way most TVs work. There is something in the codec that is not telling the computer media players that the video was mad with anamorphic pixels.

    This is like my camera that shoots 1440 x 1080 in stead of 1920 x 1080.

    I am surprised that the computer software doesn't recognise this in your footage. Is there a setting in your media player that will handle this before you go down the route of looking for something that doesn't really exist. ie if you have to alter a video in any way it will loose something. therefore can not be lossless but just loose less.

    If you are unsure that something was loseless ie with AVIRecomp, then it's probably good enough.

  3. #3

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    How are your capturing your footage? Whatever program you are currently using you just need to find an option for anamorphic.

  4. Default

    I'm sure that you will find that your camera is recording anamorphic: widescreen squashed into 4:3.

    The problem here is that when you write the DVD you will have to transcode your video so that you have a compliant DVD. If you don't use the right codec then your video won't play in a domestic DVD player. This means you will have to do some kind of conversion at least once.

    If I recall correctly you can use anamorphic video with DVD, so changing the aspect ratio is not required, but you do have to make sure you select the right options when encoding the DVD to flag the content as 16:9.

    If you're not scared of a bit of command line; I found a link to doing this with mencoder and dvdauthor: Jameser's Tech Tips: Tip #34: Creating DVDs with Free Tools in Windows XP
    You would just change the -v parameter to dvdauthor to 16:9

  5. #5
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    Quote Originally Posted by wpp8 View Post
    What I am really after is a piece of freeware that opens the file, does the aspect ratio conversion and resaves - without lossy recompression

    I have done the conversion successfully using AVIRecomp - but I'm unsure if this has been a lossless operation?
    Let's just clarify a couple of things. You will not lose any resolution by converting standard definition avi to DVD. Standard definition and the DVD definition are both 720 x 576 pixels (in PAL land or 720 x480 in NTSC) whether widescreen or not. The only difference is that when you display widescreen the pixels are wider. This is (sort of) what other posters are referring to when they say your footage is anamorphic. I suspect what you are seeing on the PC isn't 4:3, but rather square pixels. In fact the pixels for a 4:3 standard def PAl aren't quite square.

    This is the case will all cameras shooting standard definition. Any DVD authoring software ought to allow you to force your input to be recognised as widescreen.

    However you cannot ensure that converting to DVD is a lossless operation. DVDs use the MPEG-2 format which is a more lossy codec than the standard def avi you are starting with. Think about it, dual layer DVDs hold about 8.5GB data - one hour of standard def avi runs to 13GB - all that data has to go somewhere!
    Tim

  6. Default

    PAL DV has pixel aspect ratio of 1.0926 (marginally wider than square) and PAL DV widescreen has pixel aspect ratio of 1.4568 (quite a bit wider than square). Switch the project properties (or something similar in your software) from the former to the latter and it should be fixed without loss. If it's NTSC then the equivalent numbers are 0.9091 and 1.2121.

  7. #7
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    Quote Originally Posted by bouldersoundguy View Post
    PAL DV has pixel aspect ratio of 1.0926 (marginally wider than square) and PAL DV widescreen has pixel aspect ratio of 1.4568 (quite a bit wider than square). Switch the project properties (or something similar in your software) from the former to the latter and it should be fixed without loss. If it's NTSC then the equivalent numbers are 0.9091 and 1.2121.
    Thanks for putting the actual numbers to my post!
    Tim

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