Media Encoder H.264 export = poor sky quality

G

Gary Huff

Carbonite Member
I have a project in Premiere CS5.5 shot on an HPX-170 in 1080 24pa, and it looks great in Premiere, but once I export certain scenes that involve the sky, I get gray, blocky artifacts.

Sample video here (11MB)

In the sample video you can see it in the top left-hand corner. Other videos have had it on the top right hand corner as well. The sample was rendered at 2-pass VBR with 10mbps as the target and 12mbps as the maximum, Use Maximum Render Quality and Render at Maximum Depth are both checked. Level is 4.0 and profile is Main. I have tried both High profile, doing 2-pass VBR @ 25mbps, and all kinds of different things, yet the problem is still there. I tried the MPEG-2 Blu-ray preset, and it looks fine. The WMV 1080p preset is slightly better, but does have some random blockiness scattered about in the sky area.

The thing is, this isn't the first time I've shot the sky, and I've never seen this before.
 
Gary Huff said:
I have a project in Premiere CS5.5 shot on an HPX-170 in 1080 24pa, and it looks great in Premiere, but once I export certain scenes that involve the sky, I get gray, blocky artifacts.

Sample video here (11MB)

In the sample video you can see it in the top left-hand corner. Other videos have had it on the top right hand corner as well. The sample was rendered at 2-pass VBR with 10mbps as the target and 12mbps as the maximum, Use Maximum Render Quality and Render at Maximum Depth are both checked. Level is 4.0 and profile is Main. I have tried both High profile, doing 2-pass VBR @ 25mbps, and all kinds of different things, yet the problem is still there. I tried the MPEG-2 Blu-ray preset, and it looks fine. The WMV 1080p preset is slightly better, but does have some random blockiness scattered about in the sky area.

The thing is, this isn't the first time I've shot the sky, and I've never seen this before.
Click to expand...

I couldn't run the clip at 23.976, QT 7 indicated frame rates of like 11-12...

When I loaded the clip into premiere and 'stepped' through frame by frame, I didn't see any artifacts in the sky area in general, or top left corner in particular.

As a note. 10 mbs for HD material is quite low, like too low... 25 mbs should work, as HD broadcast fits into 20 (or so) mbs ATSC signals... but then perhaps they set other parameters to
get better compression, and drop 'color' info or whatever to reduce the bit rate enough to fit.
 
It plays at full frame rate for me. This is for web distribution after post production correct? Even at double size the compression artifacts in the sky/cloud gradient are well within what I would expect for hand held footage with that compression and bit rate.
 
Yeah, strangely enough, I finally played it in a player other than VLC, and it looks fine. So must just be a bug in VLC. Very strange.
 
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