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Odd resolution from uncompressed capture

 
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leeoverstreet
(MXO2 Mini)




Joined: 04 Jul 2005
Posts: 16

PostPosted: Sat Nov 12, 2016 5:15 pm    Post subject: Odd resolution from uncompressed capture Reply with quote

Why would I get a non-standard resolution (720x486) when capturing an analog NTSC source like a VHS tape, via s-video, into Premiere 2015.2 as 8-bit uncompressed? Capturing as Matrox MPEG-2 I-frame at the default 25Mbps gives the proper 720x480.

I finally noticed the incorrect resolution after wondering why a couple of recent DVDs and YouTube videos were particularly soft and blurry. Clearly it was due to scaling away those 6 pixels. Super frustrating.

So, why would uncompressed capture add 6 vertical pixels???

[ SYSTEM: Windows 7 64-bit, i7-4790k 4GHz, 16MB RAM, nVidia Ti750-based video, 256GB SSD, 2x3TB RAID-1's, Matrox MXO2 mini
VCR: JVC HR-S9911U ]
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Matrox_Support_Sam
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Posts: 6879

PostPosted: Mon Nov 14, 2016 2:22 pm    Post subject: Reply with quote

This is standard resolution for Uncompressed 8-bit for NTSC signal:
https://en.wikipedia.org/wiki/Uncompressed_video#Storage_and_data_rates_for_Uncompressed_Video

Please see the User Guide on page 89 for a workaround to this workflow:
Exporting an NTSC or 486p sequence to Adobe Premiere Pro 720x480 formats
ftp://ftp.matrox.com/pub/video/doc/Matrox%20MXO2%20Installation%20and%20User%20Guide_8.0.pdf
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Sam
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leeoverstreet
(MXO2 Mini)




Joined: 04 Jul 2005
Posts: 16

PostPosted: Tue Nov 15, 2016 6:14 pm    Post subject: Reply with quote

Thanks, Sam! Further reading after I posted my question revealed this.

I'll see if I can get good results with the workflow mentioned on page 89. Haven't tried that yet. Might also just crop 6 pixels from the bottom for videos destined for YouTube since I'd rather not see those distorted VHS lines at the bottom anyway.
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Matrox_Support_Sam
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PostPosted: Wed Nov 16, 2016 9:54 am    Post subject: Reply with quote

No problem, let us know your results.
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Sam
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leeoverstreet
(MXO2 Mini)




Joined: 04 Jul 2005
Posts: 16

PostPosted: Wed Nov 16, 2016 1:59 pm    Post subject: Reply with quote

OK, yes, much better. Very obviously sharper results. Thank you again, Sam.

Some related questions...

1) What exactly is it doing there to maintain the proper aspect ratio and keep it sharper? If I flip back and forth on the export window between "scale to fill" and "scale to fit" (the default I was doing), the scale to fill setting appears to zoom in, presumably by 3 pixels on all sides.
2) How does that transformation not lose detail as most any scaling does?
3) Am I correct that a DVD I make by this method would appear slighty more overscanned on a television than it would if I captured 720x480 (not uncompressed 486) and exported to DVD as 720x480?

Maybe I'm overthinking things but it's fascinating, and like every video enthusiast with OCD tendencies, I want to see just how good I can make these old family tapes look. Smile
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Matrox_Support_Sam
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PostPosted: Wed Nov 16, 2016 3:44 pm    Post subject: Reply with quote

Glad to hear it looks better. Not sure how the scale to fill/fit works as this is an Adobe setting and as for 720x480 vs 720x486, you can search some forum references as this: http://forum.videohelp.com/threads/373078-Is-overscan-area-included-in-digitizing-720-X-480-video
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Sam
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leeoverstreet
(MXO2 Mini)




Joined: 04 Jul 2005
Posts: 16

PostPosted: Thu Nov 17, 2016 1:42 am    Post subject: Reply with quote

Sam,

Didn't mean to make you speak for Adobe. Smile Just thought you might have some insight as to what happens in the 720x486 to 720x480 conversion.

I've done a good many searches on the topic of 486 vs. 480, and learned that 486 was the analog standard back in the day, but that 480 was used as the nearest multiple of 16 to make the binary math work for DV and the like. Lots of technical discussion out there but none that I could find really detailing scaling from one to the other, and what the ideal way to do it is. And really, I can find no explanation as to why 486 is used as the uncompressed resolution (for Matrox or anyone else) when everything else is 480. So now I'm not even sure if my plan to edit from uncompressed is worth the effort. Someone out there knows, but the internet isn't helping me find them.
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Matrox_Support_Sam
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PostPosted: Thu Nov 17, 2016 11:11 am    Post subject: Reply with quote

Thanks for the information. If you find any further information, definitely send us the link. I will also do the same.
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Sam
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