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-   -   AVCHD quality drop in complex scenes (https://www.dvinfo.net/forum/general-hd-720-1080-acquisition/531439-avchd-quality-drop-complex-scenes.html)

Nick Mirro March 20th, 2016 09:13 PM

AVCHD quality drop in complex scenes
 
Hello. I am shooting wildlife scenes with an XA20 (1080p60) and find a big quality drop in highly detailed scenes. When shooting prairie grass or a brambly forest thicket, the quality drops noticeably. Kind of reminds me of a wide shot in a sporting event, including thousands of fans. The detail seems disproportionately low.

Sunlight on this sort of scene greatly worsens the problem. What causes this?

Besides avoiding busy backgrounds and midday light, are there any other tricks or adjustments that might minimize it (aperture, SS, framerate...)?

Noa Put March 21st, 2016 01:22 AM

Re: AVCHD quality drop in complex scenes
 
It's the codec that is breaking up, try to shoot the same scene at 30p and see if that makes any difference.

Ron Evans March 21st, 2016 06:20 AM

Re: AVCHD quality drop in complex scenes
 
Or if you want smooth motion 60i. Lot less stress on the processor to encode. Shutter 1/60 and use ND filter to get iris in the f4 range.

Ron Evans

Chris Harding March 21st, 2016 07:27 AM

Re: AVCHD quality drop in complex scenes
 
Definitely the codec! If you zoom up the image (before it pixellates totally) take a look at the dense areas and you will find they already have pixel blur. It's supposed to be the fact that the processor speed for 50 or 60P needs to be a minimum od 50 mbps .... I also found that double frame rate (50 or 60P) tends to posterise areas that are a little over exposed ... tough at weddings when the bride has a white dress and the groom a black suit ..if you blown out the whites posterization gets bad. Dropping to 25 or 30P solves the issue or shoot interlaced and drop the footage onto a 25 or 30P timeline if you don't want any blur!

Jeff Pulera March 21st, 2016 08:35 AM

Re: AVCHD quality drop in complex scenes
 
Record to an external device at a higher data rate, for instance Atomos Ninja 2. Records to high-quality Apple ProRes 422 codec, or Avid DNxHD. Can make a huge difference.

I don't believe it records 1080p60, but then I don't think your camera actually outputs 1080p60 either via HDMI - more likely the HDMI output is 1080i which Ninja 2 would record.

Thanks

Jeff Pulera
Safe Harbor Computers

Wacharapong Chiowanich March 22nd, 2016 03:27 AM

Re: AVCHD quality drop in complex scenes
 
It looks like you need an external recorder as suggested above if you want to avoid this problem. This is not specific to your camera but to most cameras that record to highly compressed formats. I remember when I had the Sony EX1R as my main workhorse a few years back. It's 35Mbps XDCAM-EX recording was great for normal shooting but created noticeable blocky artifacts and loss of details similar to your experience with your camera when shooting highly detailed subjects/background. Not until did I go up to 100Mbps or even 200Mbps MPEG-2 on a Convergent Design recorder, the details of the tree branches and swaying leaves would look clean.

There really is no getting around that if you want to continue using your current camera and maintain the detail in your footage of the kind of scenes you describe.

Nick Mirro March 22nd, 2016 01:01 PM

Re: AVCHD quality drop in complex scenes
 
1 Attachment(s)
Wow really interesting, thanks.

For editing, I use VideoStudio x8.5. The XA20 records at 1080p, 28mbps with LPCM xlr.

Am a little confused following a test. I assume the hdmi out is uncompressed and so should look better live than camcorder playback of a recording of the same complex scene.

I just tested this by aiming the camcorder out the window at a live oak (not the scene below) in full sun midday and moving in the wind. The live image (watching on 1080p TV) looked about the same as the playback. Is that right?

The attachment is a screenshot in the worst possible conditions. It is only cropped on the sides from orig. Assuming exposure, focus is corrected, would higher bitrate produce a significant improvement?

Chris Harding March 22nd, 2016 06:00 PM

Re: AVCHD quality drop in complex scenes
 
Hi Nick

Have you tried MP4 mode? The XA20 allows both AVCHD or MP4 ... My Panasonics also have the same choice and I tend to use MP4 even at 1920x1080 because my cameras don't have a 4K option in AVCHD ..In MP4 I haven't seen any of the problems that AVCHD seems to have with complex images. It might be an idea to try the MP4 format 1920x1080 50P and see if it's better (it does have a higher bitrate too (35mbps against 28mbps) That would be worth a try???


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