Strange "blocks" in the image from the FS700?

V

Viktor Schroeder

Member
Hi guys,

I noticed something that appears to be on a few of my clips - especially low light, with a bright light source.
It looks very pixelated, but hugeeeee pixels. More like blocks.

I attached a screendump from the raw footage. Have any of you seen that before?
Blocks.jpg
 
Are you shooting 60fps? I noticed I get more blocky artifacting on 60fps than I do 24fps. If so, it's because the 24mbps data rate stays essentially the same between 24 and 60fps.
 
Viktor Schroeder said:
Hi guys,

I noticed something that appears to be on a few of my clips - especially low light, with a bright light source.
It looks very pixelated, but hugeeeee pixels. More like blocks.

I attached a screendump from the raw footage. Have any of you seen that before?
View attachment 61308
Click to expand...

What decoder/player are you viewing the footage with? Could you upload an uncompressed screengrab? Otherwise its hard to tell which particular artifacts you you are talking about.
 
I got some worse examples than this when filming a Bio-ethanol explosion in 200fps slowmo. Distance footage was fine, but closeups from the explosion was horrible an unusable. Looks like the codec cant keep up.
 
Yes, I filmed it in 60 fps PS mode. Is that in fact lower bitrate than 30 fps FX, since it doubles the framerates?

I tried in VLC, Premiere and AE, and it's the same artifacts!

Yeah, probably the codec that can't follow! Well, it's only 24 mbit/s... I hope it will get higher. Even the GoPro shoots in 35mbit/s now..
 
Viktor Schroeder said:
Yes, I filmed it in 60 fps PS mode. Is that in fact lower bitrate than 30 fps FX, since it doubles the framerates?

I tried in VLC, Premiere and AE, and it's the same artifacts!

Yeah, probably the codec that can't follow! Well, it's only 24 mbit/s... I hope it will get higher. Even the GoPro shoots in 35mbit/s now..
Click to expand...

Oh you shot 1080p/60 PS, not S&Q? PS is uses less than half the bitrate per frame compared to 24p FX. 24p FX 24Mbps gives you an average of 1Mb/frame, PS gives you an average of 0.46Mb/frame... I wonder if it uses significantly different quantization and GOP settings as well.

That could be a big part of your problem. But in general fast fluid/non-compressible motion will always have some chance of falling apart when using a motion-based codec. For that content, its definitely worth considering using an external recorder with higher bitrates or at least using the highest quality internal recording the camera offers which is FX. I'd also say you'll likely have even less artifacting shooting high motion fluid/fire at higher framerates like 60fps S&Q or even 120 or 240fps SSM since there will be less motion difference between each frame but it still gets the same bitrate per frame. Of course you'd have to want the slow motion look though.
 
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