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-   -   MPEG IMX compression looks really bad! (https://www.dvinfo.net/forum/convergent-design-odyssey/493483-mpeg-imx-compression-looks-really-bad.html)

David Odell March 23rd, 2011 10:38 AM

MPEG IMX compression looks really bad!
 
Hi,

this problem is related to these specs:

Panasonic HPX170 using DV output through SDI
Nanoflash with IMX compression set at 40mbit per sec.

I have used the DV compression lots of time with the DVX camera. But for these occasion I felt that using the IMX compression on the HPX+Nano to be able to record the 2 hour long take. Since the IMX has 4mb/sec instead of the 3,6mb that the DV compression has, I hopped would result in a much improved picture. But unfortunately I didn't test the compression before I had to start shooting. Attached is a IMX compressed picture from the take. Secondly is a DV compressed picture from another take. I can assure that it isn't the lack of lightning since there are sequences that has a bit of overexposure, but the quality still is lacking.

1: IMX compression from Nanoflash

2: DV compression internal from DVX100 (non A or B)

Is the picture actually this bad? In that case, its really really bad the option is even available to use! I would choose the DV camera any day over this bad quality coming from HPX+Nanoflash.

The picture is exported from Final Cut. So the DV footage is actually a bit better on a AVID station.

Anyhow, I would be happy to know if there is any possible way to handle the material so it wouldn't look so bad. Anyone have any experience with MPEG IMX 40Mbit/sec?

Thanks a lot!

Chris Hurd March 23rd, 2011 02:32 PM

Re: MPEG IMX compression looks really bad!
 
Have you got any other sample frames that are
a bit more family friendly? There are high school
students that use this site.

Dan Keaton March 23rd, 2011 02:38 PM

Re: MPEG IMX compression looks really bad!
 
Dear David,

You have your choice of using IMX 30, IMX 40, and IMX 50.

The quality of IMX 50 is supurb.

However, in-camera downconversion from HD to SD sometimes leaves a lot to be desired.

When you were using the DVX, there was no in-camera downconversion.

I recommend that you connect a high quality SDI monitor to your SDI output, then setup the camera to output a SD-SDI output, then carefully examine the images on the monitor.

If the nanoFlash is not faithly reproducing what you see on your monitor, then we will investigate further.

David Odell March 24th, 2011 01:16 AM

Re: MPEG IMX compression looks really bad!
 
1 Attachment(s)
Hi,

Chris, sorry these were the ones...

Dan, thats right, the IMX 50 is really good. I there fore got supprised the IMX 40 didn't work out propperly.
Of cource one should always dubble check the signal and so forth. But this recording was very speciall, no time, no preparation, no retakes.

Bellow is a sample from a job I did and recorded IMX 40 (40mbit/sec), and if you compare this sample with the previous I uploaded this looks fabulous! Unfortuantely since this recording isn't anywhere as important, compared with the other one.

So IMX 50 is the thing to do...

Best,
David


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