Sony AVC encoder; blocking and artifacting

farss wrote on 6/15/2009, 5:47 AM

Are you entirely certain the encoder is totally to blame here?

Lots of things happen in a dissolve as you're adding two pieces of video together. Add something at 50% to something at 1% and you get something at 51%.
That sounds trite however what you might have done is make invisible blocking / artifacts in the source blacks visible. Not only are they visible they're possibly going to stress the codec as well.
I've seen this happen with HDV from the V1 camera, try lifting the blacks a bit and major yuck.

Bob.

blink3times wrote on 6/15/2009, 6:06 AM

"Are you entirely certain the encoder is totally to blame here?"

Yes

I have looked at the source frame by frame (zoomed in) and looked at it directly from the cam. It is clearly not in the source

This does not happen when I render to M2V (with the standard 1920x1080 Blu Ray template or with main concept encoder when going over to mp4. It only happens when rendering with the Sony avc encoder.

I know beyond a doubt that the encoder is to blame and what I'm actually trying to do here is get some repro's from others so that I can hand in a ticket on the issue. I have heard a similar complaint on the encoder but it wasn't on this forum... trying to collect some data on THIS forum for SCS (If they don't know about it then they can't fix it)

I'm at work right now but will try and post some pics later when I get home.

farss wrote on 6/15/2009, 6:26 AM

OK, fair enough.

So from what you're saying I should be able to repo this from any HD footage so long as it's being encoded by the Sony avc encoder?

I ask because we now have a couple of CX100 AHCHD cameras but I couldn't get any footage off them for a couple of days. I do have on hand some low light noisy footage from my EX1 that I could use to test this for you once my Vegas machine is free.

If that shows the problem we should only need 2x 1 second clips and a project with one dissolve to show the problem. All of that would be small enough to zip up and upload along with the trouble ticket.

Bob.

Xander wrote on 6/15/2009, 6:32 AM

I tried rendering to AVC using the Sony codec a couple of times and saw blocking and artificating both times - thought it may have been due to the smartrendering. I haven't bothered using it since then. I still render to MPEG-2 as it provides the best visual quality so far.

blink3times wrote on 6/15/2009, 9:24 AM

"I tried rendering to AVC using the Sony codec a couple of times and saw blocking and artificating both times "

Yup... thanks.
It's the same in V8 and V9.
I'll put a ticket in on it and see what they say.

blink3times wrote on 6/15/2009, 4:22 PM

Just a sample pic of what I'm seeing (not exactly the same frame between the 2 captures... but the idea is illustrated)

musicvid10 wrote on 6/16/2009, 9:24 AM

The MainConcept AVC encoder has several options not found in the Sony encoder. One of them is a deblocking filter which is good in motion and transition areas, esp. at lower bitrates. Another advantage of the MainConcept encoder is 2-pass VBR. The Sony encoder is CBR, I think, so it does not take advantage of higher bitrates in motion and transition areas.

The only disadvantage I can see is that you have to roll your own templates in MainConcept.

othersteve wrote on 6/16/2009, 9:43 AM

Wait, so people have actually gotten the 2-pass VBR encoding to work with Mainconcept? I've never been able to make that happen; I always receive an error.

Steve

musicvid10 wrote on 6/16/2009, 9:56 AM

Works here.
Vegas 8.0c
Vista 32
XP Pro

TGS wrote on 6/16/2009, 10:06 AM

I can even do 2 Pass CBR in Main Concept, if I wanted.

blink3times wrote on 6/16/2009, 10:21 AM

Yeah, but the only option for mainconcept avc is MP4, is that not correct?

I haven't tried it but won't it recompress in dvda?

blink3times wrote on 6/16/2009, 5:33 PM

For those interested....

Samples have been asked for (and sent) to SCS for further investigation. I will let you know what they say as I hear.

srode wrote on 6/16/2009, 6:05 PM

I've seen blocking and artifacts in AVC and MPEG2 when zooming in on a single frame - without transitions with my SR11 as the source - I don't see it when rendering to AVCHD 1920x1080 - I don't use disolves though - mostly simple cross fades. I like AVCHD overall as a better rendering code - smaller files and better quality IMHO

TGS wrote on 6/16/2009, 6:18 PM

It may be re-sampled in DVD-A. I wouldn't use mp4 for DVD's (not yet, but it can look good), but mp4 is what YouTube and others want.
Main Concept's highest bit-rate for mp4 is off the chart. Expect instant death, if you try that one
My last 10 minute YouTube video was 768MBs and that was regular DV filling up Hi-Def size at 10,000,000 CBR. (technically, it looked pretty bad, but the original source was extra grainy due to low light, some of the fill in looked ok)
YouTube then re-encoded it in Hi-Def to 153MB size

farss wrote on 6/16/2009, 6:53 PM

"Main Concept's highest bit-rate for mp4 is off the chart. Expect instant death, if you try that one"

I don't know about the highest bitrate but a reasonable 4/2Mbps is indeed instant death to V9. Not to worry, I'll render it out to a decent intermediate and then encode it in V8.0b.

Just keep sending those crash logs in, they gotta get the message soon.

Bob.

blink3times wrote on 6/16/2009, 7:20 PM

"It may be re-sampled in DVD-A. I wouldn't use mp4 for DVD's"

Yeah... that leaves the Sony avc encoder for me (going to Blu Ray) and I can't use it because of the above noted problem :(

blink3times wrote on 6/16/2009, 7:26 PM

"I've seen blocking and artifacts in AVC and MPEG2 when zooming in on a single frame - without transitions with my SR11 as the source - I don't see it when rendering to AVCHD 1920x1080"

Interesting.... tell me more, because the above screen grab is from the SR11 (render with the standard Blu Ray AVC template (1920x1080-60i) I get blocks with a simple clip (no crossfades or anything). Just throw the clip on the time line and render..... I get blocks. Granted these are lower light shots... the full light shots look okay.

teaktart wrote on 6/16/2009, 10:04 PM

When I rendered some fast ocean kayak surfing footage for Youtube the Sony AVC version was definitely inferior, major blocking, artifacts, and fuzzy....

I used good old .wmv ( 3-5mb) for the best HD I could get within the Youtube specs.

Eileen

srode wrote on 6/17/2009, 3:28 AM

Blink2times: the blocking / artifacts are most noticable in sections of the video with continuous single color like skies or walls - capture a frame with this type of image and zoom in on it - you will likely see it These types of scenes are similar to the frames you posted above.

I haven't tried the Bluray AVC template - may try that next to see what happens. The original material from the SR11 viewed with Sony PMB doesn't show these problems - only after a render on Vegas to either MPEG2 (even high bit rates) or AVC.

With Vegas 9 skipping long GOP rerender and it working well in DVDA without rerendering - I really don't see much reason to render to anything but AVCHD though. Have you tried the same material you used above with AVCHD 1920x1080 as the render format?

blink3times wrote on 6/17/2009, 4:15 AM

Thanks....

By the sounds of it you're pretty much describing what I'm seeing as well.

This is now my only stumbling block from going completely to avc from start to finish. At present I'm working with avc on the time line (with a LOT of assistance from dynamic preview) and then going to Blu Ray as mpeg2. (M2V/AC3 to DVDa) This works fine.... quality is quite acceptable, but it knocks out the "no recompress" rendering.... and I don't get as much on the disk.

If SCS can clear up this final hurdle (and fine tune the preview a bit more) then Vegas will be about the only NLE around that can truly and natively handle all aspects of (main profile) avchd from start to finish.

srode wrote on 6/17/2009, 4:22 AM

why not follow through with AVCHD rendering start to finish? Are you seeing a disadvantage with that or are you just experimenting / testing other options?

blink3times wrote on 6/17/2009, 5:09 AM

I can't render to avc without seeing the blocking/artifacting. As you noted the blocking is clearly seen on solid surfaces (as the above screen grab points out) This is the only issue left (as far as I can see) that keeps me from going avc all the way from import to editing.... then to Blu Ray. Until this is cleared up I have no alternative but to stick with mpeg2 as a final output.