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Upscaling wrong aspect ratio and frame sized GoPro media to HD 16:9 ratio scaling to fit produces anamorphic HD 1440×1080 unexpectedly
Our production involves regularly working with GoPro footage. For reasons we’re still investigating, the camera appeared to have set itself midway through the shoot to a 960p preset which means a 1280×960 frame size with 47.95fps frame rate. What we wanted and set it to before departure was 1920×1080 25fps.
This has meant that since the footage is critical there’s been no choice but to simply resize the video during the transcode for editing stage. I’ve done this using Adobe Media Encoder and decided that the bests compromise we can attain is increasing the scale of the 1280×960 source footage to fill the 16×9 1920×1080 output frame we require was by means of cropping the top and bottom and therefore not distorting the frame. The exact increase in scale appeared to automatically worked out by Adobe Media Encoder by selecting the ‘scale to fill’ option in the output tab of the encode preset window. The output frame size is set at 1920×1080 and my chosen transcode codec is XDCAM HD 1080i50 (35 MBs/VBR), we’ve decided that the different frame rate issue will be best resolved by use of Avid’s timewarp feature within Avid when we come to edit. I also selected the ‘use maximum render quality’ checkbox to hopefully try to help mitigate the quality loss incurred from the scaling.
The transcodes have turned out pretty well all things considered but something curious has happened and I can’t figure out where in the chain this is occurring or why. The footage generated is 16:9 and HD but it appears to be anamorphic 1440×1080 footage which presumably must have a 1.33 PAR. None of my settings have specified this so I can’t quite figure out why it would end up that way.
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3 Replies
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Please post a screen capture of your encoder settings.
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Hi,
Thanks for replying here is a screenshot of my encoder window
and here is additional information in the basic video settings pane
it hasn’t actually turned out to be a problem as the pixels are the correct aspect ratio to fill a widescreen at 1920×1080 but it’s just unexpected and I’d like to know what’s happening especially if there are unintended consequences in future.
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Thank you for posting the information. I think the 35Mpbs/VBR setting uses 1440×1080 with rectangular pixels. Change to 50Mbps for 1920×1080 with square pixels. This should also give you 4:2:2 chroma sub-sampling instead of 4:2:0.
Here is some additional information for your reference:
XDCAM, XDCAM HD, and XDCAM EX Format Specifications
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