Quantcast Capturing HDV in ProRes422? - digitalFAQ Forum
  #1  
01-11-2021, 09:39 AM
jt_retro jt_retro is offline
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Hi Folks

I have some footage recording on an HDV tape. My camera (Sony HVZ-Z1E) has 1080i output via component. My workflow is entirely Mac based.

I'm fully aware that I "should" be capturing this footage via Firewire direct to some bit-for-bit HDV format stored on my computer. But in the spirit of experimentation, I'm doing something a bit different...

I'm hoping for some comments on my workflow, and any tips on where i go next.

Camera Component Output (1080i) -> Component to HDMI converter -> Elgato Camlink4k (USB) -> Quicktime saving in ProRes422.

My understanding from reading some marketing from Elgato is that the camlink doesn't do any compression and sends the raw interlaced stream to the computer via USB.

After capturing in ProRes422, I have to say I'm very pleased with the result. However, I have some questions:

- The footage is indeed interlaced as I can see the lines breaking. However, when looking at the file in Mediainfo, is says "Scan Type: Progressive". Is this an issue? Quicktime doesn't have any options for saving. FWIW, playing back the file in VLC and selecting some deinterlace options does indeed work very well, albeit the playback is slow when using Yadif (I assume the bitrate of the file is just too big for realtime deinterlacing using Yadif)

- Media info and VLC also say the file is 25FPS. Is this an issue, given the source was 50i?

- What is the best way to deinterlace this on a mac, without buying FCP?

- Apple claims that ProRes422 is a very high quality codec. However, I understand that there is some loss compared to just capturing raw HDV. How much damage would I have done to my video? Since ProRes422 is used as an intermediate format, I assume that it's "ok" to use it in my workflow?

Thanks

Last edited by jt_retro; 01-11-2021 at 10:01 AM.
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  #2  
01-11-2021, 11:45 AM
latreche34 latreche34 is online now
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You can try but it will not end well since HDV is an interlaced format and the newer devices want progressive, So go ahead and experiment and after you're done get a firewire card and start doing it the right way.
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  #3  
01-11-2021, 12:42 PM
jt_retro jt_retro is offline
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I'm not sure I understand when you say "newer devices want progressive". The Camlink accepts 1080i natively; most NLEs etc can also work with progressive footage, not to mention that most broadcast is still done 1080i (at least here in Europe). I don't believe the mere fact that the video is interlaced is an issue. Indeed, using firewire would also lead to interlaced captured video.....that would probably be re-encoded to an intermediate format such as ProRes422 anyway.

Thanks
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  #4  
01-11-2021, 03:29 PM
latreche34 latreche34 is online now
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Let's assume for a second you're right, Why would you want to take an HDV lossy MPEG-2 video, decode it from mpeg-2 then convert it to YPbPr analog, then convert it back to digital with an analog capture device and then encode it again to another lossy format? The proper workflow is to transfer the files to computer via firewire, De-interlace with QTGMC, resize from 1440x1080 (16:9) to 1920x1080 (16:9) for a square pixel ratio, and encode to h.264 with ffmpeg. No HDMI, no component, no NLE, no BS, pure quality preservation.
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  #5  
01-11-2021, 09:08 PM
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Quote:
Originally Posted by jt_retro View Post
But in the spirit of experimentation, I'm doing something a bit different...
Camera Component Output (1080i) -> Component to HDMI converter -> Elgato Camlink4k (USB) -> Quicktime saving in ProRes422.
I guess?
You have to watched the interlace, and you need to be mindful of multiple chroma changes.

Quote:
My understanding from reading some marketing from Elgato is that the camlink doesn't do any compression and sends the raw interlaced stream to the computer via USB.
That ... no.
I don't even know where to start with that sentence. Just no.

Quote:
- The footage is indeed interlaced as I can see the lines breaking. However, when looking at the file in Mediainfo, is says "Scan Type: Progressive". Is this an issue? Quicktime doesn't have any options for saving. FWIW, playing back the file in VLC and selecting some deinterlace options does indeed work very well, albeit the playback is slow when using Yadif
It's a mess with a workaround.

Quote:
(I assume the bitrate of the file is just too big for realtime deinterlacing using Yadif)
Yes.

Quote:
- Media info and VLC also say the file is 25FPS. Is this an issue, given the source was 50i?
Maybe? Probably.

Quote:
- What is the best way to deinterlace this on a mac, without buying FCP?
QTGMC via Hybrid (yes, Mac version!)

Quote:
- Apple claims that ProRes422 is a very high quality codec.
It can be, yes.

Quote:
However, I understand that there is some loss compared to just capturing raw HDV.
Uh ... no. This is one of those loaded sentences that is based on faulty understanding. Sort of like asking "How do I make my cat not bark so much?" Huh? --- HDV is less than ProRes specs ... so ... yeah.

Quote:
Since ProRes422 is used as an intermediate format, I assume that it's "ok" to use it in my workflow?
Yes.

Quote:
Originally Posted by latreche34 View Post
You can try but it will not end well since HDV is an interlaced format and the newer devices want progressive, So go ahead and experiment and after you're done get a firewire card and start doing it the right way.
Sounds a bit harsh, but often accurate.

Quote:
Originally Posted by jt_retro View Post
I'm not sure I understand when you say "newer devices want progressive". The Camlink accepts 1080i natively; most NLEs etc can also work with progressive footage, not to mention that most broadcast is still done 1080i (at least here in Europe). I don't believe the mere fact that the video is interlaced is an issue. Indeed, using firewire would also lead to interlaced captured video.....that would probably be re-encoded to an intermediate format such as ProRes422 anyway.
Thanks
I think the issue lies with the weird fps/etc that you're seeing in the files. Something isn't set correctly, somewhere, in the software settings. Maybe even the hardware?

Quote:
Originally Posted by latreche34 View Post
Let's assume for a second you're right, Why would you want to take an HDV lossy MPEG-2 video, decode it from mpeg-2 then convert it to YPbPr analog, then convert it back to digital with an analog capture device and then encode it again to another lossy format?
There are valid reasons. DV transfer is still rough, even now. It's not a perfect data transfer, even if it should be in theory. Again, theory v. practical application. I capture DV both ways, direct via Firewire and via analog lossless.

Quote:
No HDMI, no component, no NLE, no BS, pure quality preservation.
When that works as desired, it is best. But it's not the only transfer that can still end with high quality results. It's just the main method, even the suggested method.

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  #6  
01-12-2021, 07:15 AM
jt_retro jt_retro is offline
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I think there may be some misunderstanding of what I'm trying to do here. I'm not looking for information on the "best" way to capture my HDV footage because I'm already aware the best way is to capture a bit-for-bit (in theory) copy of the HDV tape via firewire.

I am here to learn about video capture and codecs and to experiment. I want to try to do something a different way, learn and understand the trade-offs and *why* something is inferior and to *what extent*. Indeed, this HDV footage was captured in Christmas 2020 - if I wanted to best quality, I would have just used a better camera!

lorsmurf, I have a few questions to your comments:

- What is the issue with the Elgato Camlink 4k device? I understand that they make a lot of game capture units but this device is designed for connecting cameras. Based on this reddit comment from Elgato (here), the interlaced frames are sent to the computer. Is this incorrect? If you have any tips on how I can test my elgato, please let me know. Also, if there is a good HDMI capture device for the computer that you're aware of, please let me know.

- Can you please explain why my captured ProRes422 footage is a mess? Is media that is saved as 25p, but is actually recorded from 50i a bad thing? Mathematically, 25p = 50i, but I don't understand codecs well enough to see where things will go wrong so I'd be grateful for help.

- My statement "However, I understand that there is some loss compared to just capturing raw HDV" perhaps wasn't wored correct. All I meant to say was that I appreciate that I'd be better off capturing raw HDV via Firewire, rather than transcoding to ProRes422. Is this wrong?

Please help me understand the inner workings here.

Thanks
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  #7  
01-12-2021, 07:51 PM
cbehr91 cbehr91 is online now
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Not sure why you'd want to capture using component video as it's still analog. I highly doubt it's Mac compatible, but I had good results capturing HDV with a Matrox MX02 using my camera's HDMI output. I agree with latreche34: For a 1:1 copy of your videos use a FireWire cable and a HDV capture utility like HDVSplit, but again no idea if that's Mac compatible. In college we had HDV cameras and used Macs, but captured to a proprietary Avid codec with awful Media Composer.
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  #8  
01-12-2021, 08:09 PM
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Quote:
Originally Posted by jt_retro View Post
lorsmurf, I have a few questions to your comments:
- What is the issue with the Elgato Camlink 4k device?
I never said there was an issue with it. In fact, I never said anything about it. I'm neutral on it, in this conversation.

Quote:
Based on this reddit comment from Elgato (here), the interlaced frames are sent to the computer. Is this incorrect?
That comment doesn't even make sense. Specs are progressive, then he/she mentions interlace. Huh?

Quote:
Also, if there is a good HDMI capture device for the computer that you're aware of, please let me know.
I'm not for it (again, neutral), but I'm actually NOT against Blackmagic or Magewell for HD sources. It's just SD sources where those cards are worthless. I've just never had any real need for HD analog capturing. It's either digital-shot HD, or analog SD (or digital DV SD).

Quote:
saved as 25p, but is actually recorded from 50i a bad thing?
Yes. You have interlaced content in progressive container. That's actually how lossless AVI is, due to no interlace flags, but ProRes422 has the flags.

Quote:
Mathematically, 25p = 50i,
No.

Quote:
but I don't understand codecs well enough to see where things will go wrong so I'd be grateful for help.
NLE misinterpretation, for starters.

Quote:
- My statement "However, I understand that there is some loss compared to just capturing raw HDV" perhaps wasn't wored correct. All I meant to say was that I appreciate that I'd be better off capturing raw HDV via Firewire, rather than transcoding to ProRes422. Is this wrong?
I don't see that it's any worse than the time where I can SD DV25 over analog. There are valid reasons, and the loss is minimal due to the camera optics.

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  #9  
01-18-2021, 10:13 AM
jt_retro jt_retro is offline
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Thank you LordSmurf.

It seems like the main issue here is the fact that Quicktime is assuming that the input is progressive, thus capturing the footage as such.

Is there any free or cheap software I could use on my modern mac to capture from my Elgato Camlink in a high quality codec (such as ProRes 422), that will allow me to capture interlaced? I guess ideally I'd use a Windows PC with Virtualdub and HuffYUV, but hoping for something on the Mac.

Also, regarding my interlaced-video-saved-as-progressive ProRes file from above, if I simply manually set the deinterlace options in VLC, have I "fixed" (albeit manually) the issue, or would there be some quality drop? I'd really like to understand the pitfalls of having such a file.

Thanks
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