Moire

Mark Fry · January 7th, 2015, 09:42 AM

It's no surprise that 4K to SD conversions suffer from moire. It's a risk whenever one down-converts from a higher to a lower resolution format. It happens when the detail in the original image is smaller than the target format can resolve and there's any movement in the frame. It has always been a problem when converting HD to SD (DVD), and used to be a huge issue when shooting video on multi-megapixel DSLRs, because of rather simplistic internal down-conversion, though the latest models seem to be rather better.

In the early days of HD, the only really reliable method was to use some very expensive hardware boxes, because someone had expensive patents on the methods. The down-conversion subroutines in NLEs varied widely in their competence. Pinnacle/Avid Liquid does quite a decent job (but on MPEG2 formats only, and now discontinued); Premier Pro appeared to be less good (judging by several commercial DVDs where I know the software the producers used), but hopefully has been improved in recent years.

The quality of the final output is a big factor in deciding whether (or more likely, when) to get a 4k camera. Most of my customers are only able to view HD or even SD DVD, so what would I have to do to get acceptable results? Which NLEs or disc-authoring programs give the best results? How long does it take? Provided 4k-to-HD can be done well in 2-3 hours for a 90 minute production, I don't mind if 4k-to-SD has to be run overnight!

Noa Put · January 7th, 2015, 10:18 AM

When I downscale 4K to HD, 4K looks more detailed then any of my 1080p camera's can produce. 4K downscaled to dvd also looks more detailed but you do see the compression artifacts, I however don't see such bad moire like Jeff is seeing, at least I didn't notice it, I did however notice that "jittering" on very fine detail and that happens in HD and on dvd, something that gets worse if you have the sharpness on your tv turned on high.

About the time it takes, rendering a 4K file from my ax100 to a 1080p h.264 file is faster then realtime on my 2 year old pc (1 hour of footage is under 45 minutes to export) I always export a hqavi file from edius to import into tmpgenc authoringworks for either blu-ray or dvd. To render a 1080p hqavi file in tmpgenc authoring works to a blu-ray disc is even faster, under 30 minutes for a 1 hour file but for this I use a separate rendercard.

Mark Watson · January 7th, 2015, 08:36 PM

I've been looking into using a hardware solution to down scale my 4K and HD video to SD. Especially after some terrible results with some video that had telephone lines draped across the scene.
Anybody know what works for that? I've looked at the AJA and BMD offerings but not sure whether those conversion boxes are exactly what I want. For the AX100, I could play my 4K video out through the camera's HDMI port into a converter box, and then from there into ???. Would I need a video recorder with and SDI input? And then from my Canon 6D or 7D, I could also play back the HD footage in camera and have it go out via the HDMI port. Looks like most of those hardware converters are really aimed at live feed conversion. Oh, and do these boxes do a better job then the NLE, handbrake, etc. software solutions?
Sorry for all the questions but I want to get the right thing on the first try.

Mark

Mark Watson · July 23rd, 2016, 03:22 AM

Decided to pursue the idea of incorporating a hardware-based solution for down-scaling my HD-quality timeline projects to DVD MPEG-2 format. I couldn't find any discussion on this topic. If the quality of a hardware solution is at least as good as what I'm getting from my current software methods, I'll be happy. I narrowed my choices down to the below listed gear. I just pulled the trigger on the JVC SR-HD2700US. What I want it to do is take my HDMI output from my laptop, while I'm outputting my HD timeline video, and downscale that HD signal to SD and save it on the internal HDD as an MPEG-2.

It can also down-convert to MPEG-2 and burn it directly to a DVD, or to both the HDD and DVD simultaneously. Might be handy for someone doing legal depositions; taking the SD or HD output directly from the camera, save as SD on the HDD, and then after the deposition filming is completed, burn the DVD(s) and deliver them on the spot.

I sure hope JVC has some good secret sauce for the down-scaling. Not sure if they do. Would feel better about a name like AJA or Video Devices in this regard, but... guess I'll find out once the device arrives.

http://www.bhphotovideo.com/c/product/1178367-REG/jvc_sr_hd2700us_blu_ray_disc_hdd.html
http://www.bhphotovideo.com/c/product/1091830-REG/decimator_dd_ducc_multi_definition_up_down_cross_converter.html
http://www.bhphotovideo.com/c/product/1091826-REG/decimator_dd_hx_hdmi_sdi_cross_converter_with.html
http://www.bhphotovideo.com/c/product/890809-REG/Sound_Devices_Pix_240i_Portable_Video.html
http://www.bhphotovideo.com/c/product/1044820-REG/blackmagic_design_teranexexp12gdl_teranex_express.html

Mark

January 7th, 2015, 09:42 AM	#16
Mark Fry Major Player Join Date: May 2004 Location: Oxford, UK Posts: 425	Re: Moire It's no surprise that 4K to SD conversions suffer from moire. It's a risk whenever one down-converts from a higher to a lower resolution format. It happens when the detail in the original image is smaller than the target format can resolve and there's any movement in the frame. It has always been a problem when converting HD to SD (DVD), and used to be a huge issue when shooting video on multi-megapixel DSLRs, because of rather simplistic internal down-conversion, though the latest models seem to be rather better. In the early days of HD, the only really reliable method was to use some very expensive hardware boxes, because someone had expensive patents on the methods. The down-conversion subroutines in NLEs varied widely in their competence. Pinnacle/Avid Liquid does quite a decent job (but on MPEG2 formats only, and now discontinued); Premier Pro appeared to be less good (judging by several commercial DVDs where I know the software the producers used), but hopefully has been improved in recent years. The quality of the final output is a big factor in deciding whether (or more likely, when) to get a 4k camera. Most of my customers are only able to view HD or even SD DVD, so what would I have to do to get acceptable results? Which NLEs or disc-authoring programs give the best results? How long does it take? Provided 4k-to-HD can be done well in 2-3 hours for a 90 minute production, I don't mind if 4k-to-SD has to be run overnight! __________________ Steam Age Pictures - videos in aid of railway preservation societies.

January 7th, 2015, 10:18 AM	#17
Noa Put Inner Circle Join Date: Jun 2007 Location: Belgium Posts: 9,510	Re: Moire When I downscale 4K to HD, 4K looks more detailed then any of my 1080p camera's can produce. 4K downscaled to dvd also looks more detailed but you do see the compression artifacts, I however don't see such bad moire like Jeff is seeing, at least I didn't notice it, I did however notice that "jittering" on very fine detail and that happens in HD and on dvd, something that gets worse if you have the sharpness on your tv turned on high. About the time it takes, rendering a 4K file from my ax100 to a 1080p h.264 file is faster then realtime on my 2 year old pc (1 hour of footage is under 45 minutes to export) I always export a hqavi file from edius to import into tmpgenc authoringworks for either blu-ray or dvd. To render a 1080p hqavi file in tmpgenc authoring works to a blu-ray disc is even faster, under 30 minutes for a 1 hour file but for this I use a separate rendercard. Last edited by Noa Put; January 7th, 2015 at 10:49 AM.

January 7th, 2015, 08:36 PM	#18
Mark Watson Major Player Join Date: Oct 2008 Location: Whidbey Island Posts: 873	Re: Moire I've been looking into using a hardware solution to down scale my 4K and HD video to SD. Especially after some terrible results with some video that had telephone lines draped across the scene. Anybody know what works for that? I've looked at the AJA and BMD offerings but not sure whether those conversion boxes are exactly what I want. For the AX100, I could play my 4K video out through the camera's HDMI port into a converter box, and then from there into ???. Would I need a video recorder with and SDI input? And then from my Canon 6D or 7D, I could also play back the HD footage in camera and have it go out via the HDMI port. Looks like most of those hardware converters are really aimed at live feed conversion. Oh, and do these boxes do a better job then the NLE, handbrake, etc. software solutions? Sorry for all the questions but I want to get the right thing on the first try. Mark

July 23rd, 2016, 03:22 AM	#19
Mark Watson Major Player Join Date: Oct 2008 Location: Whidbey Island Posts: 873	Hardware-Based HD to SD Down-Scaling Decided to pursue the idea of incorporating a hardware-based solution for down-scaling my HD-quality timeline projects to DVD MPEG-2 format. I couldn't find any discussion on this topic. If the quality of a hardware solution is at least as good as what I'm getting from my current software methods, I'll be happy. I narrowed my choices down to the below listed gear. I just pulled the trigger on the JVC SR-HD2700US. What I want it to do is take my HDMI output from my laptop, while I'm outputting my HD timeline video, and downscale that HD signal to SD and save it on the internal HDD as an MPEG-2. It can also down-convert to MPEG-2 and burn it directly to a DVD, or to both the HDD and DVD simultaneously. Might be handy for someone doing legal depositions; taking the SD or HD output directly from the camera, save as SD on the HDD, and then after the deposition filming is completed, burn the DVD(s) and deliver them on the spot. I sure hope JVC has some good secret sauce for the down-scaling. Not sure if they do. Would feel better about a name like AJA or Video Devices in this regard, but... guess I'll find out once the device arrives. http://www.bhphotovideo.com/c/product/1178367-REG/jvc_sr_hd2700us_blu_ray_disc_hdd.html http://www.bhphotovideo.com/c/product/1091830-REG/decimator_dd_ducc_multi_definition_up_down_cross_converter.html http://www.bhphotovideo.com/c/product/1091826-REG/decimator_dd_hx_hdmi_sdi_cross_converter_with.html http://www.bhphotovideo.com/c/product/890809-REG/Sound_Devices_Pix_240i_Portable_Video.html http://www.bhphotovideo.com/c/product/1044820-REG/blackmagic_design_teranexexp12gdl_teranex_express.html Mark