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Downconverting 720p30 to SD in SD Sequence
Several of us on various forums have been trying to figure our the best way to downconvert HDV material into SD. Consensus is, don’t try it in FCPro natively. Always export. This is because the HDV material when scaled down, aspect corrected, and interlaced into an NTSC sequence will look very poor compared to the exported conversion to SD via QT or Compressor. So, is that the final word? But what if you need to edit that down conversion. Or simply need to add a few shots from HDV into your SD project?
Several settings in a NTSC sequence seem to have some effect on the poor results of native down conversion. – motion sampling, fields, ect. In my case, I have 720p30 footage. One question I have is this. If I take progressive 30 (29.97) footage and drop it in a interlaced 29.97 sequence as letterbox, shouldn’t each field be exactly 1/2 the progressive frame? And if played back, will simply reproduce the whole 1/30 every two fields? (unless the sequence interprets the first field on the break between frame one and two)
In FCPro, it’s the fields that are causing me problems with the down conversion. If I turn off fields in the NTSC sequence, the 720p30 material then looks like the same material exported to SD via Quicktime. With field set to lower, or “Even” (720×486) , the image breaks up and causes aliasing in the NTSC sequence. Horizontal lines are stairstepping. Turn off interlacing and it looks 1000% better. I think I’m on to something, a way perhaps to have FCPro correctly interpret the fields of 30p source. Yet turning off fields is NOT the answer because you can’t add NTSC footage produced at 29.97i without it then looking poor.
Dave B
Dave Beaty
Dreamtime Entertainment
1625 SE 46th St
Cape Coral FL 33904
239-549-4081
800-446-7575
da**@********************nt.com
http://www.dreamtimeentertainment.com -
7 Replies
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[Dave Beaty] “Several of us on various forums have been trying to figure our the best way to downconvert HDV material into SD”
Through hardware. We can downnconvert 720p and 1080i to SD in realtime via the Kona boards and it’s perfectly pristine. If this is a standard workflow for you, then you should have hardware downconversion.
We also never edit HDV natively. We always convert it to DVCPro HD or ProRes during capture through the Kona boards.
Walter Biscardi, Jr.
https://www.biscardicreative.com
HD Editorial & Animation for Broadcast and independent productions.All Things Apple Podcast! https://cowcast.creativecow.net/all_things_apple/index.html
Read my blog! https://blogs.creativecow.net/WalterBiscardi
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That’s because you are taking your progressive footage and making it interlaced. Those are artifacts. Do what you are doing and change the field order to none in the NTSC sequence and render. No harm no foul in doing so.
Jeremy
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Dave –
“If I take progressive 30 (29.97) footage and drop it in a interlaced 29.97 sequence as letterbox, shouldn’t each field be exactly 1/2 the progressive frame? And if played back, will simply reproduce the whole 1/30 every two fields? (unless the sequence interprets the first field on the break between frame one and two)”
Yes. But this creates an odd interlace that looks all wrong on an NTSC monitor. With apologies to Walter, I have tried this on a Kona LH too, with the same poor results you describe. It looks like NTSC’s much courser cousin. Diagonals have short black serrations and horizontals blink horribly. And this is viewing NTSC Component on a Sony PVM NTSC monitor with the video in motion. It also looks the same when played back from Beta tape. Maybe Walter could post more details on his downconversion setup, ’cause it’s not working for me.
When I posted on this before, I had an off list email exchange with Graeme Nattress on the subject. His comment was true progressive HD clips can’t be interlaced. If it’s not encoded that way when it comes off the CCDs, you can’t add it later.
Maybe Graeme can jump in and expand on that a bit.
George
Light Images -
George,
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> I have tried this on a Kona LH too, with the same poor results you describe. It looks like NTSC’s much courser cousin. Diagonals have short black serrations and horizontals blink horribly. And this is viewing NTSC Component on a Sony PVM NTSC monitor with the video in motion. >Exactly, I have both Kona LH and Multibridge Pro on two system hooked up via component to Sony BVM’s and Panasonic plasmas. As I understand it, Multibridge is software conversion but Kona LH is hardware. Both look the same when downconverting the 720p sequence to NTSC. Aliasing on the fine detail.
If I export a HD sequence to QT 10 bit NTSC and it looks so so much better than both the Kona LH downconvert and the downconvert by putting clips directly in an NTSC sequence.
Using media manager and recompressing a sequence to a new 10-bit uncompressed sequence also looks very good and this the path I am using to mix HD and SD in an NTSC project. I will finish the edit in HDV, then recompress and re-edit the NTSC elements and CC in 10-bit. This also gives me the change to tweak gfx that sometimes don’t look proper in the plain down converted movie.
You may see this program later this year on PBS. John Paul II : A Saint For Our Times. See what you think of the results.
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>I had an off list email exchange with Graeme Nattress on the subject. His comment was true progressive HD clips can’t be interlaced. If it’s not encoded that way when it comes off the CCDs, you can’t add it later. < I would dissagree with this. Like I said, 1 frame of 30p (29.97) footage should be seperated into 2 fields playing back at 1/60 (1/59.94) sec each resulting in an exact reproduction of the frame. Perhaps I am missing something in this logic? I'd leave the sequence as progressive, but I want to add NTSC clips to the edit, which are interlaced, thus defeating that plan. So - using media manager to recompress the HD is the only path until Apple figures out a way to properly interpret 720p30 clips in NTSC timelines. I have not experimented with scaling and aspect's role in this problem, I suspect it is also key. As I believe that 720p30 clips that are placed in NTSC sequences that have no scaling will play and look properly. On another subject, the HDV that I edit natively looks great and the sequence is quite responsive, really no distracting slow down. As long as I don't try to render a bunch of FX or color correction into HDV, it looks great. Thanks to the new render codec setting in sequence settings, we can now totally avoid that and render transitions and effects into any compressed or uncompressed codec. I've have used Kona component caputre to DVCProHD on several projects 2 years ago when FCPro did not support 720p24 HDV, but abandoned that practice because the gains vs using native were not worth it to us. We compared work flows, disk space usage, time savings, output quality and came to this conclusion. Others may have had other experiences. Dave Beaty Dreamtime Entertainment 1625 SE 46th St Cape Coral FL 33904 239-549-4081 800-446-7575 dave@dreamtimeentertainment.com
http://www.dreamtimeentertainment.com -
Dave –
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If I export a HD sequence to QT 10 bit NTSC and it looks so so much better than both the Kona LH downconvert and the downconvert by putting clips directly in an NTSC sequence.I just tried this with Export/QT Movie and Export/Using QT Conversion – Then out through Kona set to 525 10 bit component to the PVM. It looks exactly the same as the direct Kona conversion here. All of the same artifacts.
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Using media manager and recompressing a sequence to a new 10-bit uncompressed sequence also looks very good and this the path I am using to mix HD and SD in an NTSC project.I tried this too and no luck. Still looks the same.
Can you give more details on the setting? Are you using a different ouput that doesn’t go through the Kona?
A real 10 bit uncompressed BetaSP sequence output through the Kona looks perfect, so I don’t think it’s my system. JVC 720p60 out through the same Kona settings I use for 720p30 looks normal too.
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1 frame of 30p (29.97) footage should be seperated into 2 fields playing back at 1/60 (1/59.94) sec each resulting in an exact reproduction of the frame. Perhaps I am missing something in this logic?It’s something to do with 30p I think. I was hoping Graeme would pop in and explain it more. When I suggested he make a filter for interlacing clips that need to go to NTSC, he said “Can’t be done”. I sent a Beta tape to AJA support. They thought it looked awful, sent to engineer then then emailed to say “That’s normal. 720p30 always looks that way”
Everyone else I’ve talked to say “It works great on my system”, so something doesn’t add up.
Maybe I need to set something I missed when I tried your export methods.
George
Light Images -
What about 720p footage shot at 60p? Shouldn’t it be possible to recreate standard NTSC interlaced video from that? If not, can somebody please explain why? I’m currently trying to figure out how to interlace footage shot with the EX-1 at 60p in order to use it together with standard-def footage.
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[David Burch] “Shouldn’t it be possible to recreate standard NTSC interlaced video from that?”
Yes. Each progressive frame of 59.94p gets segmented to a field to get you 59.94i fields per second (or 29.97 frames per second).
Jeremy
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