Nex 5N - Compressed vs Uncompressed Video Example

Started Nov 28, 2011 | Discussions
paulcurtis
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Nex 5N - Compressed vs Uncompressed Video Example
Nov 28, 2011

I mentioned in another thread that i would upload an example.

EDIT: Okay the jpeg compression from the drp gallery has destroyed the differences between the images. I will have to see if i can find another way of hosting the image: any ideas?

I did a test, comparing the compressed AVC video (highest settings) with recording the uncompressed HDMI output to uncompressed video (via a Blackmagic Shuttle onto SSD).

You can see that the compression does (obviously) make a difference. This scene wasn't being whip panned nor does it have a lot of motion in. So i wasn't attempting to 'break' the compression either.

You can see that the uncompressed has a lot more detail, you can see some colour aliasing on the sat dish, which is hidden by compression munge on the other example.

If you look at colour channels you can see the effects of the 4:2:0 sampling as well.

What is more interesting is that on the compressed version you can see some dark blue horizontal lines on some bricks to the right. This is very odd, it's a very digital artefact and the uncompressed version does not have this. This looks like a compression mistake.

These are small crops blown up 200% (nearest neighbour) for display. They are a little soft, focus was on the bricks in the back but through a CV 28 lens which is a little soft due to the coatings. However the uncompressed very would sharpen up quite nicely.

The same shot with my canon dSLR would have looked like moire city.

So the NEX5N is actually a capable video performer. But as per my other thread, the HDMI out overlays stupid graphics that can't be turned off. So it's not useable yet. What great potential for such a tiny cam.

hope this is of interest to some

cheers
paul

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paulcurtis
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Re: Nex 5N - Compressed vs Uncompressed Video Example
In reply to paulcurtis, Nov 28, 2011

It appears i can't edit the above message more than once.

If you can download the original, it's a JPG at 100%, it's not perfect but it does illustrate the differences better than the inline preview size which is much lower quality.

I'm not aware of a photo hosting service that would serve out original PNG files. Flickr doesn't from that i can see either...

cheers
paul

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physguy88
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Re: Nex 5N - Compressed vs Uncompressed Video Example
In reply to paulcurtis, Nov 28, 2011

Paul,

You took the uncompressed video by running an HDMI out during video recording at 60p? Are you sure the HDMI out is not already compressed? Do you have full size frame grabs?

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npires
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Re: Nex 5N - Compressed vs Uncompressed Video Example
In reply to paulcurtis, Nov 28, 2011

Can't download the original you've got it set to private. Can see the uncompressed is sharper when you compare the lines between the bricks.

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kaktusss
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Re: Nex 5N - Compressed vs Uncompressed Video Example
In reply to paulcurtis, Nov 28, 2011

You need a flickr pro account to see the original file.
If you want a free service, dropbox is the easiest way to go :
http://db.tt/t10Xghl

Just put your picture in the "public" folder, right click on it then choose "copy public link", paste it where you want

It's a shame the HDMI output shows the (pixellated) NEX GUI, makes it totally useless.

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paulcurtis
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Re: Nex 5N - Compressed vs Uncompressed Video Example
In reply to physguy88, Nov 28, 2011

physguy88 wrote:

Paul,

You took the uncompressed video by running an HDMI out during video recording at 60p? Are you sure the HDMI out is not already compressed? Do you have full size frame grabs?

I was running 25p, there's no easy way to record 60p off HDMI right now.

Yes, the HDMI is pre compression, the frames quite clearly show this.

I will do some more tests to check dynamic range but i expect that to be 8 bit. In most cases the AVC is actually pretty good. But uncompressed does give better detail and a lot less break up during movement.

One of the reasons i wanted to try this was to see how bad the AVC is compressing in the shadows, that's the area of an image that most compression solutions take huge liberties with. But so far the AVC does a good job.

I'm also trying to quantify what the DRO and various settings do to the video image, to see what is the best way to capture. I will be comparing the latitude to an EX1 that i have laying around too. At some point i should be able to compare to an F3/FS100.

The gallery image is set to public, and the original should be downloadable. I've just checked. So is it possible to download and look at that?

I will look at the flickr pro account although i'm not a big user of flickr, so it may not make sense for me

cheers
paul

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physguy88
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Re: Nex 5N - Compressed vs Uncompressed Video Example
In reply to paulcurtis, Nov 28, 2011

OK, now I'm beginning to understand what the Blackmagic Hyperdeck does. Wow, what a product! Do you get sound as well as video? The huge storage requirements make it impractical for amateurs like me, but I can imagine the video quality would be amazing, and you'd be able to use ISO 6400 and up to boot.

Looking forward to seeing the gallery images. I'm actually tempted to buy this thing, even though processing the footage is completely impractical for me.

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rinkos
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Re: Nex 5N - Compressed vs Uncompressed Video Example
In reply to paulcurtis, Nov 28, 2011

sry man i have edited quite a few movies by now...its a pain in the Arsss to edit even the "low quality" AVC files .given their size (1000 clips or so ) ..uncompressed its much much worse...more then i can bare and have patience for.

more over i like my movies to be able to be passed around so i need it in a format all people can see AVC is that ( even that is not playable today at many's people computers since they are too old slow etc ) /

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paulcurtis
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Re: Nex 5N - Compressed vs Uncompressed Video Example
In reply to rinkos, Nov 28, 2011

It depends what you shoot, if you're not doing reality or events and are on drama/scripted then uncompressed is okay. The SSDs are like film canisters with their run times.

The blackmagic is a bit of a toy really, just experimenting with it, but the workflow isn't so bad. There are much more sophisticated recorders out there

1) Shoot uncompressed onto SSD

2) Take out SSD, plug it into a esata-FW800 cable into the Mac, copy off files at speed (there should be a eSata -> thunderbolt soon too)

3) Import into final cut pro and make optimised ProRes files whilst you do it. Chuck away the uncompressed if you want too and use the ProRes as masters.

Having said that the studio version of the shuttle can record DNxHD with a firmware update although BM haven't said yet whether that's possible on the portable shuttle.

Also uncompressed for certain types of shot that compression doesn't work too well with.

The real reason i'm experimenting is to see how i can use the NEX5N personally.

cheers
paul

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jazzroy1972
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Re: Nex 5N - Compressed vs Uncompressed Video Example
In reply to paulcurtis, Nov 28, 2011

I'm really interested in it, I was planning of having a similar workflow.
I guess you are using the Hyperdeck Shuttle, right?

How do you perform your recording?

The Nex-5n if connected with the HDMI cable switches off its LCD, so, how do you control the view?

Does the Shuttle have a "through" option allowing you to put an extra HDMI-in monitor?

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paulcurtis
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Re: Nex 5N - Compressed vs Uncompressed Video Example
In reply to jazzroy1972, Nov 28, 2011

jazzroy1972 wrote:

I'm really interested in it, I was planning of having a similar workflow.
I guess you are using the Hyperdeck Shuttle, right?

How do you perform your recording?

The Nex-5n if connected with the HDMI cable switches off its LCD, so, how do you control the view?

Does the Shuttle have a "through" option allowing you to put an extra HDMI-in monitor?

Well, firstly petition sony in japan to make a change to their next firmware that gives us NEX5N users the ability to turn OFF all the extra display rubbish on the HDMI out. It's just a firmware thing. And the closest you can get is to extract a 2.35 chunk from the top of the 1080 by half pressing the shutter to get rid of the menu graphics and leave just the recording/time labels at the bottom. So not practical at all right now!

Then, yes the hyperdeck shuttle has HDMI in and HDMI out, so you'd need to be monitoring through the shuttle. The shuttle is just very simple. You press the record button. Then stop it. I don't believe it can be triggered from the camera. The shuttle will play back what it's recorded but there is no UI. It's like a half finished product really, there's a DISP button which does nothing and the BM docs say it's for a future firmware update.

It's very basic, but that means it's simple. 64GB SSD will run for about 6 mins i think, so multiples of 64 would scale accordingly.

Prices of SSDs are becoming more acceptable, so that's not really an issue.

hth
paul

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krisspy
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Re: Nex 5N - Compressed vs Uncompressed Video Example
In reply to paulcurtis, Nov 29, 2011

The two pictures look absolutely identical to me!

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sfoskett
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Re: Nex 5N - Compressed vs Uncompressed Video Example
In reply to paulcurtis, Feb 10, 2012

Reviving an old thread...

Can someone with a NEX-7 say whether it's possible to turn off all the icons and text and stream pure, plain video over HDMI? I have a Blackmagic Shuttle on order and would live to be able to stream live, uncompressed video from my (forthcoming) NEX-7 to the Mac over Thunderbolt.

Thanks in advance!

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