25p question - it looks interlaced!

[John Hewat]

I have created a 1080i25 project with 25p footage from my V1 in Premiere Pro.

I output the file as a 1080i25 AVI without selecting the 'de-interlace' option.

For the first time I can view the footage on my new High Definition monitor, and I can now see interlaced lines in this apparent 25p footage.

I've attached some screenshots. They're not re-sized, I've just cropped the edges. What you see here is the exact pixels from my footage with clear interlaced lines. If you look closely at the edges they are obvious.

Can someoene tell me what I've done wrong in the workflow?

I record 25p, I capture into a 25i project and create a 25i AVI, right? This is what I have been told repeatedly to do. Because the 25p footage is imbedded in an interlaced stream, right?

Do I need to de-interlace afterall?

[Piotr Wozniacki]

John,

1. The 25PsF from the V1 is embedded within a 1080/50i stream, with 2 fields per each frame, but without any temporal difference between them (while interlaced video also has 2 fields, but taken 1/50 sec aprat).

2. With Premiere, you can use the 1080/25 (50i) template (not 25i), but when exporting, you need to choose field order "none" (progressive). However, you do not switch deintelacing on.

3. Why would you want an uncompressed HD avi, anyway? It's best to use MPG-2!

Hope this helps.

PS. I can't see any screenshots attached:)

[John Hewat]

MPG-2?

Really? Gees, I'm behind with my knowedge. How can MPEG be better than uncompressed? What are the optimal settings for that?

I've added the screenshots but you were right with your solution. The lines are gone. However, the file is almost 100Mb smaller than the original and I reckon that I can see a quality degradation in all the footage. Is that possible or am I imagining it?

[Piotr Wozniacki]

John,

Whether you use uncompressed avi or compress to mpeg depends on your intended use of the resulting file. Uncompressed can be used for easier editing (as proxy files, usually of lower resolution), but if you are going to deliver as full HD, you must compress it somehow!

[John Hewat]

Originally Posted by Piotr Wozniacki

but if you are going to deliver as full HD, you must compress it somehow!

Can you clarify this? I don't really know why. If I keep the movie as a file on my computer is there ever a need to compress to MPEG2? I understand that for DVD delivery I will need to turn it into an MPEG but for storage as a file, why must it be compressed?

And to do so, I need to use the Adobe Media Encoder, right? I hate navigating the settings on that thing. MPEG2 doesn't even allow me to output in Full HD, it forces me to compress to SD.

[Piotr Wozniacki]

Originally Posted by John Hewat

Can you clarify this? I don't really know why. If I keep the movie as a file on my computer is there ever a need to compress to MPEG2? I understand that for DVD delivery I will need to turn it into an MPEG but for storage as a file, why must it be compressed?

And to do so, I need to use the Adobe Media Encoder, right? I hate navigating the settings on that thing. MPEG2 doesn't even allow me to output in Full HD, it forces me to compress to SD.

John - of course if you're going to keep all movies on your computer's HDD, you may have them uncompressed, but why?!! Yo will soon run off the disk space!

Also, encoding as MPEG-2 does not imply going SD at all. You can define your frame size as 1440x1080 or 1920x1080, and your bitrate accordingly.

[John Hewat]

Originally Posted by Piotr Wozniacki

John - of course if you're going to keep all movies on your computer's HDD, you may have them uncompressed, but why?!! Yo will soon run off the disk space!

So the quality loss is negligable enough not to worry about it?

Originally Posted by Piotr Wozniacki

Also, encoding as MPEG-2 does not imply going SD at all. You can define your frame size as 1440x1080 or 1920x1080, and your bitrate accordingly.

You're right, I've just discovered that! But I'm always dissatisfied with the results of MPEG conversion. Also, do you advise choosing the 1080 25p option for output or 50i? And what is the recommended BitRate? Should I force it to be as high as possible?

[Piotr Wozniacki]

Originally Posted by John Hewat

So the quality loss is negligable enough not to worry about it?

John, we could talk about quality loss in mpeg encoding if you were shooting and capturing uncompressed in the first place. You don't - unless you're doing something non-standard, your V1 does the mpeg-2 compression before writing to tape. Also, when you capture the usual way (ie through firewire), you're getting an mpeg-2 file (in the transport stream format).

So, rendering to avi will only have one possible use: if your system is not robust enough, it will make editing easier. But it will never bring back the quality lost due to the mpeg compression!

Originally Posted by John Hewat

You're right, I've just discovered that! But I'm always dissatisfied with the results of MPEG conversion. Also, do you advise choosing the 1080 25p option for output or 50i? And what is the recommended BitRate? Should I force it to be as high as possible?

Well, again the answer depends on your application; but yes - you should always try to use the highest bitrate available (ie. applicable to the output format and not too hard for your given computer system). Of course, with HDV there is no point in going higher than its original bitrate of CBR=25mbps (though you may choose to save some space using VBR with the max bitrate of say 30mbps).

BTW, I'd appreciate a comment from somebody more knowledgeable: with VBR, does it really make sense to set the max bitrate any higher than 25?

[John Hewat]

Originally Posted by Piotr Wozniacki

Also, when you capture the usual way (ie through firewire), you're getting an mpeg-2 file (in the transport stream format).

Thaks very much for all your advice and help - one last question though - when I caupture from my V1 into PPro 1.5.1 I get an AVI rather than an mpg or m2t. Does that mean that I am doing something other than the usual way?

[Piotr Wozniacki]

Originally Posted by John Hewat

Thaks very much for all your advice and help - one last question though - when I caupture from my V1 into PPro 1.5.1 I get an AVI rather than an mpg or m2t. Does that mean that I am doing something other than the usual way?

Ouch... Everything I said before was based on the assumption you were capturing HDV (with PP 1.5 you need a HD add-on, I think). Follow these steps:

-are you shooting SD or HD?
-if you're shooting HD, and getting avi's at capture, you're capturing SD! Check in the camera menu whether you have i.Link Conv ON; if so turn it OFF
-if your PP 1.5 can even see the camera with i.Link Conv OFF, you need to upgrade your PP to support HD!

[John Hewat]

Originally Posted by Piotr Wozniacki

Ouch... Everything I said before was based on the assumption you were capturing HDV (with PP 1.5 you need a HD add-on, I think). Follow these steps:

-are you shooting SD or HD?
-if you're shooting HD, and getting avi's at capture, you're capturing SD! Check in the camera menu whether you have i.Link Conv ON; if so turn it OFF
-if your PP 1.5 can even see the camera with i.Link Conv OFF, you need to upgrade your PP to support HD!

Holy cow - now I'm even more confused. I am shooting HDV and capturing HDV and getting AVI files. I'm aware of all the options you suggested changing if I was doing it wrong and can guarantee I'm getting 1440x1080 HDV AVI files.

[Piotr Wozniacki]

Originally Posted by John Hewat

Holy cow - now I'm even more confused. I am shooting HDV and capturing HDV and getting AVI files. I'm aware of all the options you suggested changing if I was doing it wrong and can guarantee I'm getting 1440x1080 HDV AVI files.

Do you have Cineform stuff installed? It could explain things (the mpeg is converted to avi on-the-fly, during capture). Other than that, I can't help you much further:)

Anybody?

[John Hewat]

Originally Posted by Piotr Wozniacki

Do you have Cineform stuff installed? It could explain things (the mpeg is converted to avi on-the-fly, during capture). Other than that, I can't help you much further:)

Anybody?

I had a trial that a mate gave me but it expired long ago.

Should I worry that my footage is compromised because of this?

[Piotr Wozniacki]

Originally Posted by John Hewat

I had a trial that a mate gave me but it expired long ago.

Should I worry that my footage is compromised because of this?

John, are you 100% sure you're capturing HDV? Can you check it in the properties after importing a captured clip into the timeline?

If it is HD avi indeed, and you're capturing without any "special treatment" (like Cineform intermadiates) - than it beats me.

[John Hewat]

Originally Posted by Piotr Wozniacki

John, are you 100% sure you're capturing HDV? Can you check it in the properties after importing a captured clip into the timeline?

If it is HD avi indeed, and you're capturing without any "special treatment" (like Cineform intermadiates) - than it beats me.

I've attached a screenshot from Premiere and also the properties window from a right click in Windows Explorer that show it is HDV.

That said, it also lists the compression codec as Cineform, though I am under the impression PPro 1.5.1 uses Cineform natively, I certainly don't have anything like Aspect HD installed.