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Down-Converting 1080p to 720p

Aug 9, 2011 2:43 PM

I shoot AVCHD 1080p form a verity of different cameras - but 99% of all my final projects are for the Web or DVD - no big screen and no blue-ray. I want to shoot what I can in 1080p for future use or projects.  My question is what is the best solution (free or nominal fee) for down-converting my footage to 720p for storage and editing?

 
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    Aug 9, 2011 2:49 PM   in reply to csgaraglino

    Why downconvert? You can use 1080p footage in a 720p sequence, simply by scaling it down or using the Scale to Frame Size preference or command. It'll save tons of time and space.

     
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    Aug 9, 2011 11:28 PM   in reply to csgaraglino

    The size of the copies depends on the bitrate used, frame size has little to no bearing on the matter.  In order to get half the size, you'd need half the bitrate.

     

    I'd agree with Colin on this one.  Don't worry about copies, use the originals.

     
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    Aug 10, 2011 9:57 AM   in reply to csgaraglino

    Can I ask a related question here? (maybe in the "dumb question department) ...

     

    I'm also shooting with a brand new NX5U -- which lets me shoot 1080 and 720 simultaneously (one to chip, the other to a flash drive). My projects also end up on the web and non-blueray DVDs.

     

    So is the quality going to be better if I work in 1080 timelines and then import the final into a 720 timeline? Or is it going to look the same if I work in 720 right from the start?

     

    I haven't run any tests to judge rendering time, etc. I'm assuming higher rez means longer processing time. But maybe it's worth it for better quality.

     

    Anyone have any advice about this?

     

    Thanks in advance!

     
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    Aug 10, 2011 10:21 AM   in reply to Bill Matthiesen

    >worth it for better quality

     

    In general, I will say always use the best quality possible for editing

     

    I used to use a Sony 8mm analog camcorder, with a Pinnacle Dv500 card to digitize, finally going to a DVD... with "about" the same quality as a VHS

     

    I now use a Canon Vixia AVCHD... still going to a DVD... the picture quality of the DVD is MUCH better than anything I created before, since I am starting with a higher bit depth and letting CS5 take care of the downsizing and downrezzing at the end of the process

     
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    Aug 10, 2011 11:17 AM   in reply to Bill Matthiesen
    Or is it going to look the same if I work in 720 right from the start?

     

    That'd be my guess.

     
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    Aug 11, 2011 11:47 PM   in reply to Jim Simon

    I've been shooting 1080 AVCHD on a Panasonic HMC 40...recently started loading the footage into 720 sequences with really great results.

     
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    Aug 12, 2011 3:05 AM   in reply to Bill Matthiesen

    It really depends on what you're doing to the footage, and what hardware it comes from. 1080>720 isn't an integer step so there will be pixel-blending on the resize, and with most prosumer kit having chroma subsampling you're not reading complete per-pixel data in the first place.

     

    Even rendering to AVI I doubt anyone could look at an unedited 720p clip on a TV or Web video and tell if it came from a 720p capture or a scaled 1080p capture - in the former you'll have lens blur and chroma SS across pixels, in the latter you'll have fractional resampling giving near-enough the same feel, but if you apply effects that work on a per-pixel basis (such as unsharp masks or keying) to the footage before scaling they can look different. Not necessarily better or worse, just different; and your audience will only see one version so what you notice doesn't really matter!

     

    It certainly makes sense to grab the biggest frames you can on location, as aside from any future use in full-HD projects you get the option to place it at larger than "fit" size, so you have leeway to crop stuff out or stabilise motion.

     

    Prior to Mercury and solid-state drives, working in 1080 over 720 was a really noticeable drag - but now it's more about the codec than the frame size. A "tricky" codec at 480 can be more laggy to scrub than a "simple" codec at 1080, it depends on how much work your CPU has to do extracting the frame data before the MPE can scamper off with it.

     
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    Aug 12, 2011 5:02 PM   in reply to Dave Merchant

    When practical shoot at the native camera resolution. Edit native. Do any scaling at the end of the process.

     
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    Aug 12, 2011 7:01 PM   in reply to Bill Matthiesen

    I have a related but slightly different question.  I will be videoing my grandson's high school football games with my Sony NX5U.  Is there any advantage using 720p over 1080i for action events.  Last year I did not experiment and try 720p,  I used 1080i and produced primarily DVD's and an occasional BD-R

     
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    Aug 13, 2011 10:13 AM   in reply to Bill Gehrke

    Canon Vixia HFS100 AVCHD MPEG4-AVC / H.264


    http://forums.adobe.com/message/2765679 Jeff Bellune sez...
    -Use 60i for high-motion, action and sports scenes.
    -24p is good for low-motion, film-like storytelling scenes.
    -30p is virtually worthless
     
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    Aug 13, 2011 4:47 PM   in reply to Bill Gehrke
    any advantage using 720p over 1080i for action events.

     

    Yes.  Much better temporal resolution.  1080 is 30 interlaced frames, 720 is 60 progressive frames.

     
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    Aug 13, 2011 4:51 PM   in reply to Jim Simon

    Thanks Jim, I thought that should be the case.

     
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    Sep 18, 2011 3:35 PM   in reply to Dave Merchant

    Brilliant response David Merchant.

     

    Can anyone offer advice on this related situation in Premiere Pro 5,5:

     

    I have footage from a 3 camera shoot.  One of the cameras was a locked off wide shot that I now prefer it be more zoomed in.  I don't mind having the project in 720 - it's primary destination would be You Tube / Vimeo & DVD.   All which would work well in 720 as far as I am concerned.

     

    The footage was shot at 1080/24. 

     

    Could I simply edit the project in a 720 timeline, and scale up the camera track that I prefer more zoomed in?  Does anyone know what the exact scale would be for 1080 to 720?  For some reason, when I use the source file in a 720 Premiere sequence, the clips automatically scale to the sequence size.  I'd want to scale it as best I could to retain a pixel to pixel relationship to avoid blur etc.  But David, you say that it wont scale pixel to pixel with effects.  The only effect I'd use on a scaled track would be color grading (with Red Giant Looks or Colorista II).  What is the best way to do this - if there is one? 

     

    Can I at least assume this method will look better than scaling up the particular camera in a 1080 sequence? 

     

    Thanks,

    Angelo

     
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