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#1 |
Inner Circle
Join Date: Nov 2006
Location: Tallahassee, FL
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HD to SD Downconversion
Ok,
So in the past week or so, there has been a lot of talk about the footage coming out of the EXx cameras not converting to SD very well. I tried the experiment for myself last night and mine worked ok. So tonight I thought I'd give something a go. I took a reasonably clean 1080p interview, and cut a 5 second snippet out of it. I then resized it to 1280x720 and made an .mp4 file as a control. After doing that, I created a 16:9 720x405 file. From that, I created an mp4, and an mpeg2 file ready to drop into my authoring software. I uploaded all three files on Youtube, and onto Vimeo as well. You can download all three files from Vimeo from here: Perrone Ford on Vimeo The Youtube site is here: YouTube - perroneford's Channel The workflow: 1. Load 1080p .MXF file into Sony Vegas adjust exposure. 2. Render 1080p uncompressed .AVI file 3. Open 1080p .avi in Virtualdub. Resize to both 1280x720 and 720x405 and save uncompressed versions 4. Open 720p file in Vegas and render .mp4 at 6 mbps. 5. Open 405p file and render .mp4 file 6. Open 405p file and render widescreen mpeg2 file 7. Upload files to youtube and vimeo From my testing, I am able to VERY clean SD files from 1080p sources with a minimum of fuss. If virtualdub understood the MXF files, it would save a step, but it does not. This also show me that the creation of SD footage is NOT tied to the camera or the XDCamEX codec. It is entirely possible to get lovely footage at SD sizes from the 1080p original. I will do a file replacement on the Vimeo site for the 720p file so it can be seen there in HD. The Youtube one shows properly but one of the 405p files is not yet showing. I hope this helps out.
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#2 | |
Major Player
Join Date: May 2008
Location: Nuremberg, Germany
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Resizing 16:9 to 720x405 for DVD-use just doesn't make much sense. What's exactly happening in this step? Any resizing/resampling of the pixels? If no: It will look distorted on your TV, because DVDs don't use square pixels, but your 405p-file does. If yes: down to 360 or up to 480 lines? If down to 360 lines: you're using letterboxing instead of true widescreen. If up to 480 lines: You're interpolating 75 extra-lines from the 405 initial ones instead of going directly from 1080 to 480. That's sub-optimal. |
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#3 |
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Join Date: Sep 2004
Location: Chislehurst, London
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Thanks for your detailed workflow, I am sure it must work otherwise you wouldn't have posted the formula.
On trawling through this site and other I have found many workarrounds to the problem of converting HD to SD - most seem to be long winded and rather defeat the object of working with Solid State memory. Over the last two days I have burnt over 20 test DVDs trying to find the answer, each DVD had its own set of problems, the main one being artifacts on fine detail. My main reason for choosing the EX3 was that I could shoot in NTSC or PAL format, for my DVD sales the North America market is very important, if this were not the case then I may have purchased the Z7. The sollution came late last night. The EX3 has a built in downconverter, which will output files in the SD format. You do need to have a video capture card which will accept the Component video cable (RGB cable). I have a Matrox Rx2 card. From the Video Set menu select YPbPr/SDi OUT and select SD. From your NLE select Capture and set the EX3 to Media, select thumbnails and choose a video clip, press the play button and start recording the video to your computer. The footage will be added to the clip bin in much the same way as capturing from tape. OK, so it isn't as convenient as being able to drag a file straight from the card, but at least you get to review the footage as it is being imported. I will continue to find a better solution, I am sure you must be able to to downconvert a file from one memory card to another, if this is the case then you should be able to drag the files directly into the timeline. Finally, the footage captured using my technique above is perfect, certainly as good and better than anything I previously captured using my Canon XH A1. I used footage that was shot at 1920 x 1080, 1440 x 1080, 1280 x 720 interlaced and progressive, they all worked perfectly. My tests were all done using NTSC, but I will repeat them using PAL footage at a later stage.
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#4 | |||
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Join Date: May 2008
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Problems are: -the halting problem -a lot of people don't know the basics of digital media -people who don't know those basics are answering questions in forums like these, so a lot of confusion gets into them. Last edited by Dominik Seibold; December 20th, 2008 at 03:26 AM. |
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#5 | |
Inner Circle
Join Date: Nov 2006
Location: Tallahassee, FL
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I invite you to view this file which I uploaded some hours ago and I assume you have not seen: Interview 405p Mpeg2 on Vimeo That is a REAL render for DVD output from a 720x480 timeline with a 16:9 source. Here is another I was working on as I was typing: http://www.vimeo.com/2581948
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#6 | |
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Join Date: May 2008
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But then what's your posted workflow for? It's not for people who want to do DVDs, though the title "HD to SD Downconversion" let people suppose that, and it's not for people who want to upload youtube-videos, because youtube supports 720p. |
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#7 | |
Inner Circle
Join Date: Nov 2006
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So I'll say it here. If you are ACTUALLY BURNING A REAL DVD, keep your project at 720x480 for an NTSC SD DVD. PAL folks can adjust as necessary.
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#8 | |
Inner Circle
Join Date: Nov 2006
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Quote:
Make sense?
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#9 |
Major Player
Join Date: May 2008
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If people would start to post stills from their (problematic) mpeg2-results instead of writing a thousand dubious words, we could immediately tell them where the problem in their workflow is. But posting stills from mpeg2-files seems to be even harder for them...
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#10 | |
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Join Date: Nov 2006
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What I found mystifying was people saying that the CAMERA was not giving them good SD results. I just couldn't fathom that at all. If the camera is giving you stunning 1080p footage as everyone claims, then the fault is not with the camera or the codec. It's elsewhere in the chain. Here is the 720p downres of that second interview clip: YouTube - iv2 720p mpeg4
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#11 | |||
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#12 | |
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I have no problems with the camera, it is a fine instrument. All I want is to be able to produce decent quality as an end result - this may very well be down to the codecs, software etc. I am still finding out. You are right my DVD has been downgraded in quality when compared to the original footage, but then I would expect this from SD. I am not 100% there yet, but nearer today than yesterday.
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#13 |
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Which software do you use? Windows or Mac?
The first hint I can give you is to try to use some blur to make the edges softer. That will reduce mosquito-noise around edges and flickering on CRT-TVs. Also, if done before downscaling, it will reduce aliasing introduced by low-quality downscaling. Please forget your analog workaround soon. It's far from being reasonable in any way. |
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#14 |
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I use Premierre Pro CS3 (Windows) and Encore CS3. I also have a Matrox RTX2 card with its own set of Codecs.
Up to now I have been bringing the video files directly into the timeline and then using the Adobe/Matrox Media encoder to output the file ready for burning in Encore. The Media encoder Transcodes the file on the fly. Premierre also has a XDCAM EX preset which does work, although it still relies on the Adobe/Matrox media encoder to produce the DVD ready file. I suspect the encoder may be at the root of the problem.
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#15 |
Join Date: Jul 2002
Posts: 1,244
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Perrone, maybe I missed something along the way in your explanation. When making DVDs, why not render straight from the HD timeline (mfx) using MainConcept MP2/DVD Architect NTSC Widescreen Video Stream?
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