nanoFlash Public Beta 1.6.226 Firmware Comments

[Dan Keaton]

Originally Posted by Peter Moretti

Dan,

I respectfully disagree w/ that explanation. The aperture size in QT has to do with subtle differences between SD and DV frame sizes and pixel aspect ratio. It would not cause the horizontal banding that I described above.

A difference in QT Aperture can cause a difference in adding or removing black from the the borders of the entire frame, but I really don't think that's happening in this case.

HTH, and that I'm giving you the correct info.. (I obviously believe that I am.)

Dear Peter,

I tried hard, in posting the information, to convey the information provided to me.

I am not knowledgeable about Aperature settings.

And I do not understand how this information can be determined from the images Piotr posted.

But, the information came from a trusted source, but his posts, for some reason were not getting through.

Also, I am certain that the originator of the comments was not referring to your post. His email arrived in my inbox at 2 pm EST today, before your first post in this thread.

I am trying to learn about "Aperature" settings as used in this context.

[Dan Keaton]

Dear Friends,

I am wondering if the "Aperature" has application here in this discussion or not.

I believe that Piotr uses Sony Vegas Pro 10.

If "Aperature" is a Apple Quicktime or Final Cut Pro control only, and if it does not apply to the way that Sony Vegas Pro 10 displays the files, then we should discount the "Aperature" discussion.

[Peter Moretti]

Originally Posted by Piotr Wozniacki

I beg to disagree - just take a look at diagrams on Page 3 here:

http://dougkerr.net/pumpkin/articles/Subsampling.pdf

But I guess we mean the same thing - just a matter of nomenclature; better vertical resolution = more horizontal lines.

I believe we do mean the same thing. But, FWIW, the "correct" terminology is 1/2 horizontal resolution. You can see in the diagram that you referenced a "H: 1/2" next to 4:2:2.

[Peter Moretti]

Originally Posted by Dan Keaton

Dear Friends,

I am wondering if the "Aperture" has application here in this discussion or not.

I believe that Piotr uses Sony Vegas Pro 10.

If "Aperture" is a Apple Quicktime or Final Cut Pro control only, and if it does not apply to the way that Sony Vegas Pro 10 displays the files, then we should discount the "Aperture" discussion.

An Aperture setting is usually set during creating the QT wrapped file. Now if the NLE or player actually uses this setting depends on the program. Some also let you override what's set in the file. Often times slight issues in aspect ratio or garbage lines on the top and bottom of the frame are caused by an incorrect Aperture setting. So extra black info in a histogram can be the result of such garbage, but that's not what's going on here.

I have no doubt whatsoever that the nano writes the correct Aperture setting. And just because the EX uses "Production" instead of "Classic" does not mean that there is any type of mismatch. Often times different Aperture settings will yield the identical result.

[Piotr Wozniacki]

Originally Posted by Peter Moretti

I believe we do mean the same thing. But, FWIW, the "correct" terminology is 1/2 horizontal resolution. You can see in the diagram that you referenced a "H: 1/2" next to 4:2:2.

Exactly, Peter:

4:4:4 ----> H:1/1, V:1/1

4:2:2 ----> H:1/2, V:1/1
4:2:0 ----> H:1/2, V:1/2

- which means the vertical resolution is exactly 2x higher in 4:2:2 than it's in 4:2:0. Both 422 and 420 have horizontal resolution 2x lower than the full 4:4:4 sampling (and this is probably what you meant).

[Rafael Amador]

Originally Posted by Peter Moretti

Actually, 4:2:2 and 4:2:0 theoretically have the same vertical resolution. It's the horizontal resolution that's different.

But when you throw in macro blocking, bit rate and how the codec works, there can be a difference in vertical resolution as well. So the horizontal banding you're seeing is not really the direct result of 4:2:0 but a more complex combination of factors.

422 has DOUBLE COLOR VERTICAL RESOLUTION than 420.
Just have a look to a 2x2 pixels block as 4.2.0, and to the same 2x2 block as 4.2.2.
rafael

[Rafael Amador]

Originally Posted by Peter Moretti

I have no doubt whatsoever that the nano writes the correct Aperture setting. And just because the EX uses "Production" instead of "Classic" does not mean that there is any type of mismatch. Often times different Aperture settings will yield the identical result.

Peter,
The miss match is HUGE.
You simply can not cut between a picture with an aperture and the same picture with a different aperture.
The picture JUMP as when you were cutting between signal out of sync.
They have different sizes on screen.
This may be something originally designed for DV, but affects every single standard, format, size,..
Just open any QT file and switch between the different aperture options.
rafael

[Piotr Wozniacki]

Originally Posted by Piotr Wozniacki

Since this thread is about comments on the latest Beta software, here is some from me - but please do not treat them as ranting :)

After placing on Vegas timeline, and synchronizing by TC, clips recorded simultaneously to SxS (XDCAM EX HQ) and nanoFlash (220 Mbps I-Fo), I have noticed 2 things:

1. The nanoFlash embedded audio is lagging by 4 milliseconds. Not a big deal, but when mixing the two for any reason, there is a slight echo (empty bucket effect)

Dear Dan,

Just to return to this thread main subject: what do you think is causing this slight audio delay in the present Beta?

FYI, it used to be even longer with previous firmware releases (I don't know about the 1.6.29, as I skipped it).

Thanks,

Piotr

[Dan Keaton]

Dear Priotr,

How does the audio line up to a loud clap, one near the lens and near the mic?

4 milliseconds = 1/250th of a second.

May I assume that you are recording in MXF, and using an EX1, using embedded audio in HD-SDI?

I assume that you are using I-Frame Only at 220 Mbps.

[Piotr Wozniacki]

Dear Dan,

All your assumptions above are correct.

I'm not sure I understood your question, but I'll try to be more specific:

- the slight delay of nanoFlash clip (both audio and video) in relation to the EX1 internally recorded one is natural. However, I'm talking about the audio lagging behind the video inside the nano clip - i.e. after having aligned the nF and EX video with a single frame accuracy (using TC), the nF-recorded audio is still those 4 ms behind the EX-recorded audio.

As I said - not a big deal, but out of technical curiosity - what might be causing it? Both audio and video are fed to the nanoFlash simultaneously, through SDI...As is the TC, by which the video can be synchronized perfectly in Vegas Pro - but not the audio?

To synchronize the audio perfectly, I must ungroup it from the video, turn frame quantization off, and slide the audio by exactly 4 ms.

Believe me, 4 ms can be important with the kind of recordings I do. I produced a live classic guitar performance recently:

Marcin Dylla plays Rossinina at the Polish Royal Castle in Krakow on Vimeo

- and on those close-ups of the guitarist fingers, even 1 ms audio/video lag is visible!

Thanks

Piotr

Oops - I didn't realize inserting a link to Vimeo clip will open the player; this was NOT my intention as there are no close-ups I mentioned in this particular clip, which is just a sample of the DVD I made later :) But you can take my word for it - with fast passages watched on a really big screen, every string pulling must be perfectly synchronized with the sound of the string, or a person with a good ear for music will notice. I remember that while editing this video, I had to adjust the audio by milliseconds quite often...

[Peter Moretti]

Originally Posted by Piotr Wozniacki

Exactly, Peter:

4:4:4 ----> H:1/1, V:1/1

4:2:2 ----> H:1/2, V:1/1
4:2:0 ----> H:1/2, V:1/2

- which means the vertical resolution is exactly 2x higher in 4:2:2 than it's in 4:2:0. Both 422 and 420 have horizontal resolution 2x lower than the full 4:4:4 sampling (and this is probably what you meant).

Yes we agree :). And you are right concerning the comparison to 4:2:0 in terms of vertical resolution. So what I wrote about 4:2:0 not being responsible for the horizontal banding is incorrect. I knew that 4:2:0 halves the resolution in both directions, but had in my mind that 4:2:2 halves the horizontal resolution (compared to 4:4:4).

So your explanation of the horizontal banding being caused by less vertical resolution in 4:2:0 is correct. ;)


P.S. Are you sure the audio issue you're having might not be caused by mic placement? I'm sure you know that a mic placed farther away from a subject will cause delay, due to the fact that the sound traveling to the mic travels more slowly than the light traveling to the sensor. I believe the rule of thumb is that a mic 20' away from the subject will cause a one frame audio delay.

[Piotr Wozniacki]

Peter,

Of course I'm aware of the light vs. sound speed difference, but this is not the case here - I was comparing the nano recording with the EX own recording, done simultaneously, with a single microphone, and with the nano fed from the EX1 through HD-SDI.

The above is an explanation of my "4 ms audio lag in the current Beta", and NOT how I recorded the live event I mentioned later on :)

[Peter Moretti]

Gottcha. I thought that was the case, but just thought I'd ask ;).

[Adam Stanislav]

Originally Posted by Piotr Wozniacki

just a sample of the DVD I made later :)

Is that Wawel?

[Piotr Wozniacki]

Originally Posted by Rafael Amador

Thats due to the so call "Presentation".
SxS clips and NANO files use different "Aperture" , so QT display both pictures in a different fashion.
This also affects how FC canvas display the picture, and how look on the VideoScope. The difference is small but noticeable when you shift between pictures.
rafael

Thanks Rafael - your posts arrive with considerable delay, which is a great pity :(

You're probably reading this "in real time", so you're aware that some people (like Luben) also suggested the Aperture setting difference being the reason, but that has been ruled out later on the basis that my examples come from MXF files and Vegas Pro, the environment which doesn't use the Aperture parameter at all.

Nevertheless, the question remains open to Dan on why CD have chosen to encode with Aperture set to "Classic" setting while most camcorders record with Aperture set to "Production". If there are no special reasons for this, perhaps the nanoFlash could also use the latter, if only for compatibility reasons?


Piotr