Brian Alexander
Forum Replies Created
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[Chris Grose] ” I exported an uncompressed QT out of FCP 6″
Did you export uncompressed or with your current sequence settings?
[Chris Grose] “there is a significant drop in quality from the uncompressed HDV 1080i50 video”
You do know that you’re comparing your HDV (HD 1440 x 1080) to MPEG 2 (PAL SD 720 x 576). The DVD will never look the same as the original using this current workflow.
[Chris Grose] “There is some pixelation, colour loss”
Are you viewing your uncompressed file, your m2v file and your DVD all on the same monitor? What steps have you taken for troubleshooting image quality changes?
Pixelation? Are you seeing macroblocks or pixels breaking up in fast motion? Make sure you view your DVD unscaled or Actual Size. A screen shot of your video would help.
[Chris Grose] “the video has a peculiar look at times that almost seems like it has been sped-up in places.”
Is DVD Studio Pro set up for PAL or NTSC?
Alternate Workflow
When I downscale for DVD I use an intermediate codec for resizing before using MPEG 2 to create the m2v file. I use ProRes because it will keep your quality intact and it’s relatively quick compared to other intermediate codecs.
Hope this helps.
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Brian Alexander
Sr Video Engineer
Freeman AVS -
[dan freshman] “My files are currently in photo jpegs 720X486 ntsc”
Are these Photo JPG files interlaced or progressive?
[dan freshman] “What is the big difference that professional DVD authoring is doing?”
Pro DVDs are created from film transfers at 24 (23.98) Progressive frames per second.
The 24p material is encoded with NTSC (29.97) flags that trigger telecine processors in DVD players.
The DVD players output 29.97 fps. (I don’t want to rewrite the process so look here: https://en.wikipedia.org/wiki/Telecine#DVDs)
You don’t see telecine processing on TVs because TVs processors know how to deal with video fields and frames separately; there are 2 interlaced frames in a telecine sequence.
If you captured film (movie) footage from a broadcast source and played it back on your computer you would see telecine processing.
On the other hand…29.97fps (59.94 fields) played back on computers are deinterlaced (when activated) by 1 of three methods: Scan Line Duplication (hardly used), Scan Line Interpolation (single field), and Field Merging (combining fields).
[dan freshman] “What are the main differences?”
29.97 NTSC and 24fps (23.98)
Want to simulate Hollywood DVDs? Start with 24p material. That will get you one step closer to your goal.
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Brian Alexander
Sr Video Engineer
Freeman AVS -
I agree that the best idea is to leave this movie interlaced since the original footage is interlaced but…
Most commercial films on DVD are progressive frames @ 23.98fps. These files are encoded with an NTSC flag set so the DVD players know to add a 3:2 pulldown for proper display on TVs.
Now I haven’t studied DVD processing chips so maybe someone has a clearer picture on DVD hardware than I do or maybe you can point me towards a place I can learn this information (please).
What does 29.97p do on a DVD player? Is there both an interlacing processor and Deinterlacing processor on DVD players? (I’ve put 29.97p footage on a DVD and really couldn’t tell a difference between i/p with the DVD player set on both i and p).
What provides better image quality, Deinterlacing w/footage prior to DVD creation or Deinterlacing footage in hardware? (I’d guess hardware unless we were talking some high end, motion compensated Compressor deinterlacing)
Not trying to thread-jack, just wanted to clear some mysteries while the topic was fresh.
Thanks.
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Brian Alexander
Sr Video Engineer
Freeman AVS -
[Bruce Schwartz] “is there a way to force an i-frame/keyframe at a particular point in the video so that it is efficient to seek to that point during playback?”
Huh?
What are you trying to do? What codec are you trying to do it with? Are you trying to make interactivity within QuickTime? (Please explain)
You may be getting the whole point of Keyframes mixed up with something else you are trying to accomplish.
[Bruce Schwartz] “want relatively few keyframes except for the places I specify.”
Some codecs use keyframes at set intervals in a GOP structure like HDV or MPEG2. Other codec keyframes can be set to a specific number of frames (like you pointed out). When choosing an interval for keyframes the encoder will produce a new keyframe every time there is a scene change.
When scrubbing GOP based videos in QuickTime you will most likely see just the Keyframes. I would suggest using a chapter markers to get around your video. If you can provide more info that would be a big help.
Thanks.
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Brian Alexander
Sr Video Engineer
Freeman AVS -
Not all pixels (picture elements) are created equal. Most modern computer and TV displays, DLP, Plasma, LCD, and LCoS, use square pixels to re-create images from an analog or digital video signal.
Video imagers, CCD and CMOS, do not always the same square pixel formats as displays. Sometimes they use odd (not normal) pixel counts on the imaging chips then process the image to create a standard size video frame. When this happens the video is tagged with a ‘flag’ to tell the computer, monitor, or equipment how to display the image.
The aspect ratio flag is part of the ancillary data and is represented by a 4 bit code word. Unfortunately a lot of times this flag is lost in the processing of the video signal. Quicktime does not always recognize this flag (probably because it is not present).
It’s best to output assuming square pixels. If your video is distorted in QuickTime you may have to manually type in the correct pixel count (based on square pixels) to view your video distortion free. This is especially true when looking at 720 x 480 16:9 video in quicktime. Sony DVCAM products do not add this flag so the video will look squeezed horizontally or stretched vertically so manual input is a necessity to view the video distortion free.
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Brian Alexander
Sr Video Engineer
Freeman AVS -
You definitely want to choose None (Distort) when converting to square pixels for computer playback.
Converting 720 x 480 NTSC with the resize filter in Episode will give you the following results:
Cut: This crops the sides of your image. Result will be 640 x 480 but your pixels will not be corrected for aspect ratio.
Letterbox (Pad): This scales your 720 x 480 to fit inside a 640 x 480 window leaving you with a letterboxed image. Again, this does not correct the pixel aspect ratio.
None (Distort): This converts your rectangle NTSC pixels to square pixels for your computer display leaving you with a 640 x 480 image.
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Brian Alexander
Sr Video Engineer
Freeman AVS -
Uh…
There are way too many variables to go shooting off quick answers to your quick question. Do you know of a universal tape format that can be played with every tape deck? VHS, BETA, DigitBeta, DVCAM, DVCProHD, HDCAM, HDCAM SR, etc…
Photo JPG and DV are universal but they are not distribution based formats, these are for editing.
I’m at a loss for words…How about youtube? Anyone with a browser can see your video then. That’s pretty universal.
You will get solid answers from this forum if you can provide details about what you have to work with and what you are trying to do. What you are asking for is for the Mac and PC guy to hang out and watch the same TV in the same living room and maybe eat at Subway together. Not going to happen.
If you do find some universal format in your quest please let us know what you find.
Thanks.
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What about DNxHD? This may be a valid option.
https://avid.custkb.com/avid/app/selfservice/search.jsp?DocId=263545
(download link is at the bottom of the page)As Craig has stated, it all depends on what they can handle.
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Peter,
I think you’re missing one very important piece of your puzzle: DVD is Standard Def. All DVD players are SD. DVD format is an MPEG 2 (not a very efficient codec) wrapped in a .VOB container. Your 1080 sequence is going to be down-scaled to SD frame sizes for DVD formatting.Sure, you can get a DVD player that will have a DVI or HDMI port on it but it is just up-scaling the 720 x 480 (or 720 x 404) NTSC Video to 1280 x 720 or 1920 x 1080. Your $1,000 TV probably has a slightly better scaler than a $100 DVD player but that is arguable.
1080i @ 24p? How was your footage shot? Just curious, this sounds like contradiction in formats.
An MPEG2 HD @ 20 Mbps will only fit roughly 30 minutes on a 4.7 GB DVD. Are you working with blu-ray by chance?
It sounds like you may need to invest in a Blu-Ray burner or consider other options for your HD distribution.
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[Daniel Low] “You cannot access good enough H.264 output in Compressor for use as archive, as far as I’m concerned. “
Is it the Image Quality or GOP sequence that you do not like? Do you like h264 options from Episode better than Compressor’s offerings?
[Daniel Low] “I’d leave it as ProRes and given the cost per MB of BluRay discs along with how fragile they are and the low transfer rates – I’d archive to spinning disk. “
I currently have tapes sitting on the shelf that have been there for over 10 years. I can’t rely on Hard Discs to last that long until Solid State drives are ubiquitous. My current solution is to utilize BluRay discs as a storage medium. These are rarely touched. These discs will be used only when the client has lost their hard drive or we need to pull 2 minutes of footage from a 3 day meeting.
My typical workflow involves tapeless recording. I am going direct to disk using ProRes rather than using a tape based solution. My jobs consist of up to 4 sources for 8 hour hours a day for 3-4 days: Primary and Backup switched camera feed, and 2 iso camera feeds. This leaves me with 96 – 128 Hrs of footage! In ProRes (standard flavor) this equates up to 7.8 TB of video data per show. I have many many shows to support. Client takes their hard drives home and I take my hard drives back to my encoding station for processing.
BluRay discs will allow me to fit 4 hrs my HD material @ 12 Mbps+. ProRes HD files to BluRay will only allow me 20 – 25 Minutes of data.
How would you solve this dilemma?
Thanks for your input.