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PIX240 1080p video quality lower than AF100 in-camera quality ???

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Tom David
PIX240 1080p video quality lower than AF100 in-camera quality ???
on Jul 16, 2012 at 12:52:46 pm

Hello,

Is anyone else having issues with their external data recorders when recording video from the HDSDI port on the Panasonic AF100? I am when recording ProresLT with my PIX240. I have contacted the guys at SOUNDDEVICES, though am still waiting their response. In the meantime, I wanted to see if this problem was common.

I am having quality issues with recording a 1080 25p stream from an Panasonic AF101 as Prores LT.

I two frame video is downloadable here for your interest: http://www.tomdavid.com.au/downloads/Boy_in_street.mov


The Panasonic AF101 outputs a 1080i signal from its HDSDI port. The PIX240 correctly recognises this as 1080i as its input.

However I want to record a 1080P image with the PIX240, as I am shooting 1080p on the AF101.

I am recording in-camera: AVCHD 1080P 25fps
I am recording on the PIX240 via SDI: Prores LT 1080psf25

I am recording in this PSF format as my understanding is that to receive a 1080i signal via an SDI connection that is 1080p at its source (the AF101), I must interpret this as 1080psf25 to record true ProresLT 1080p (at the PIX240).

However as you can see via my attached video, and flicking back and forwards over the two frames, the AVCHD footage (24mbits) and much clearer and noise / artefact free than the Prores LT (100 mbit) footage. (I have checked, I have not got the source files muddled up – the Pix is definitely is recording more artefacts in the image). Particularly look at the child’s face and also asphalt artefacts behind him.

Can anyone please offer some feedback, as the whole reasoning behind purchasing the PIX was to bypass the in-camera recording and make the most of the HDSDI 8bit data stream. However currently it seems that the PIX240 image at Prores LT has more artefacts than the in-camera recording. Not expected!

In fact, when I push and pull the picture to extremes, I am noticing no difference in latitude, noise etc, except to say that the in-camera AVCHD is superior to the PIX240 recording.

Please help! I hope that I am doing something wrong.

I have the most recent v2 firmware update installed on the pix.

Regards,
Tom



____________________________________

Cinematography - Editing - Motion Graphics

M +61 421 176 251
E tmd@tomdavid.com.au
W http://www.tomdavid.com.au

Examples of work found at http://vimeo.com/tomdavid/albums



Cheers,
Tom

Camera Operator - Editor - Motion Graphics
(http://www.tomdavid.com.au)


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Matt Mayer
Re: PIX240 1080p video quality lower than AF100 in-camera quality ???
on Jul 17, 2012 at 1:02:03 pm

Tom,

First, you can record progressive on the PIX directly from the 1080i output of a camera. Set the scaler to record 1080p25.

Second, the ProResLT codec will have a little more noise than regular ProRes. Try a similar test using ProRes, I think your results will be better.

If you have more questions, come join us on our support forum: forums.sounddevices.com.

---Matt Mayer
Applications Engineer
Sound Devices, LLC

---Matt


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Noah Kadner
Re: PIX240 1080p video quality lower than AF100 in-camera quality ???
on Jul 20, 2012 at 7:20:04 pm

Yeah don't use LT- not meant for this as the bitrate is a bit low...

Noah

Call Box Training.
Featuring the Panasonic GH2 and Panasonic AC160/130.


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Tom David
Re: PIX240 1080p video quality lower than AF100 in-camera quality ???
on Jul 20, 2012 at 9:35:30 pm

Thanks guys - others are telling me that the Prores LT codec 'data rate is too low' also, however I don't believe this is the problem.

Remember that the in-camera recordings in my example video are also transcoded to Prores LT as well, via FCP software, and this conversion looks great compared to the real time conversion to Prores LT that the PIX240 is doing.

I am currently trying to work through these issues with a rep from sound devices now - we are also getting the same issues recording data from a canon C300 - again, the transcoded prores lt footage from the in-camera recording seems much better than what the PIX240 is achieving with its real time recording. The Pix is recording a noisier image with artifacts occurring around areas of contrast. And we are noticing tiny horizontal lines in skin tones also (and close ups in people's eyebrows).

My understanding of Prores LT is that it's data rate of 100mbps should be more than adequate to record a 50mbps HDSDI data stream with no quality loss issues - does anyone have any contrasting views to why this would be incorrect?

Thanks guys, Tom.

Cheers,
Tom

Camera Operator - Editor - Motion Graphics
(http://www.tomdavid.com.au)


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Gary Huff
Re: PIX240 1080p video quality lower than AF100 in-camera quality ???
on Jul 27, 2012 at 6:54:57 pm

[Tom David] "My understanding of Prores LT is that it's data rate of 100mbps should be more than adequate to record a 50mbps HDSDI data stream with no quality loss issues - does anyone have any contrasting views to why this would be incorrect?"

ProResLT is 50mbps, not 100.


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Tom David
Re: PIX240 1080p video quality lower than AF100 in-camera quality ???
on Jul 27, 2012 at 10:43:06 pm

Hi Gary, where did you get this info from? Please refer to the Apple Prores Whitepaper (http://images.apple.com/support/finalcutpro/docs/Apple-ProRes-White-Paper-July-2009.pdf) page 10 to confirm you have your units correct?

Cheers,
Tom

Camera Operator - Editor - Motion Graphics
(http://www.tomdavid.com.au)


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Marco Andrés Fernández Galvis
Re: PIX240 1080p video quality lower than AF100 in-camera quality ???
on Oct 26, 2012 at 11:38:04 pm

Hi Tom,

I'm interested in knowing what was the end result of the issues you were having with the PIX240 and the canon C300. 'Cause i'm having a problem when I set the camera at 50 Mbps 1920x1080 and the PIX240 at 23.98psf because the PIX 240 OSD FILE/RESOLUTION RATE appears in red. But if a set the camera at 50Mbps 1280x720 the Pix 240 OSD FILE/RESOLUTION RATE appears in white.

So I want to obtain the highest resolution rate possible.

Any suggestions?

Many thanks.


Marco Andrés Fernández
Freelance


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Tom David
Re: PIX240 1080p video quality lower than AF100 in-camera quality ???
on Oct 27, 2012 at 12:39:12 am

Hi Marco,

I haven't yet received the exact problem to my answer yet - the PIX240 realtime recording at Prores LT is still inferior it would seem to just transcoding your in camera recording to Prores LT (even if recorded incamera at 24mbit AVCHD).

They did however do some extensive testing it would seem and uncovered some oddities with outputs from the C300. This was the email they sent me describing these:

-----------------------

Hi Tom,

There are a few things I'd like to start with, and that would be to run theses tests again, but this time try using the HDMI output on the C300. We've ran a few tests with the C300 and have found some oddities about its output. Below are some tests results one of our reps found when testing the C300, that may be able to shed some light on what is going on:


Canon C300 FW 1.04.1.00

- When set for 1080 and either 23.98 [sic] or 29.97, the SDI output is 1080PsF 29.97
- When set for 1080/59.94, SDI output is 1080i59.94
- The SDI output remained PsF (at 23/29) whether the camera was rolling or not.
- I confirmed PsF output on the SDI using a Phabrix.
- With PIX Scaler set to 1080p23.976 and 29.97PsF input, the 3:2 pulldown does not activate.
- According to page 127 of the current C300 manual, the SDI output is always supposed to be 1080i, no mention is made of PsF.
- Based on the manual, wondering if this is just a bug in the C300 firmware

- HDMI output in all 1080 settings is 1080i
- 3:2 pulldown works as expected with the HDMI 1080i59.94 input.

- I recorded a ProRes 422 file with the C300 1080PsF29.97 output and PIX set to "Same as Input"

The file shows as 1080Psf29.97

The file appears to have the proper 3:2 cadence, but the duplicated frames have a visual interlace artifact. It appears that the fields are inverted.

When I import the file to FCP, I see the same artifacts as I do in QuickTime. Looking at the file metadata, there is no Field Dominance set. When I change the field dominance to either Even or Odd (doesn't matter which) that cleans up the artifacting.

A file recorded with PIX Scaler set to 1080i59.94 looks exactly the same as the "Same as input" file. No jaggies on the straight lines, but interlacing artifacts on the duplicated frames.


- I recorded a ProRes 422 file with the C300 1080PsF29.97 output and PIX set to 1080p23.976


The file shows as 1080p23.976

While there are no visual interlace artifacts, the picture appears to be bouncing, like the camera is wobbling. The camera was not wobbling, so I would guess this is another type of field inversion artifact.

Also, if you look at the window frames and mullions, you can see jaggies along the lines which is another indicator of inverted fields.

This file has duplicated frames, in a very odd cadence. In one sequence the frame cadence was: 1-6 : 7/8 : 9/10 : 11-14 : 15/16 : 17/18 : 19-22 : 23/00 : 01/02 : 3-6 : 7/8 : 9/10
Frames marked: 7/8, etc are the duplicated frames. Not sure why 1-2 at the beginning of the sequence wasn't duplicated.


- When the C300 is set for 720p, the output is 720p59.94 for all modes. The PIX immediately recognized the 3:2 pulldown cadence in this mode.

Other Notes:

- C300 has a True 24fps mode. When this is turned on 1080 output is 1080PsF30, 720 output is 1080p60.

- C300 has a genlock input. I tested it quickly with the PIX Sync out. It wasn't a proper test, but only these modes appeared to cause problems (black LCD, no SDI output):
1080p30
1080i60/PsF30
1080p29.97df
1080p29.97nd
480i59.94 ND/DF
576i50

I was kind of surprised that the NTSC composite sync caused issued. We will have to look at that further to see if it is supposed to be supported by the camera

To me, these tests would indicate there may be something going on with the C300 output, rather than the PIX's method of compressing the file in real time. Because FCP is able to sense the field dominance on the C300 internal recordings, you aren't seeing the same artifacts, but because of how the C300 is sending its output to the PIX, the field inversion can be seen much more clearly. I suspect if you import the PIX files into FCP, and set a field dominance, these artifacts will go away. You can even see the fields shift when switching between your sample files with the C300 internal and then the PIX real time, so I'm fairly confident this is what is going on. Please run this test to see if the field dominance is the issue, and also please try a few tests using the HDMI port on the C300, since the SDI port will only send out a PsF signal, it could be part if the issue. Please let me know what you find out and any thoughts you may have being provided this additional information. Thanks for your patience Tom, and I look forward to hearing from you!

Best Regards,

Stephen Fichter
Tech Support

Cheers,
Tom

Camera Operator - Editor - Motion Graphics
(http://www.tomdavid.com.au)


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