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AVCHD maximum image quality settings and testing
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  • I went back to 12 gop and it looks better as far a cadence goes.
    SP 110 4.jpg
    2679 x 1396 - 1M
  • Try some motion. Often I-frames become very small. Whenever that happens, P-frames spike up close to max I-frame size.

    I might leave GOP parameter at default 24.
  • @stonebat

    What about for 720p? Will you lower that at all? I still think 30 is just too long. Especially since I use 720p for high motion videos.
  • 720p60 GOP6 AQ3 showed worse result. You could try it with AQ0.

    For my working set, I will stay either AQ0 or AQ1 with GOP6. AQ3 for testing set.
  • I agree that there are reasons lower GOP could be good. Until Vitaliy addresses the issues with low GOP in a future release of PTools, however, I think we are flogging a dead horse.

    Chris
  • I like 3.62d :)

    AQ0 or AQ1 seems good enough for now... until we get 3.63d (???).

    You know what we are hoping for. AQ4!!!
  • I think with low AQ settings and low GOP you are just lowering quality to the point where bitrate never gets high enough for the problem to manifest itself - so there may not be much of a visible improvement. I'm with you - AQ4 would show much better - but I think we'll have to wait a bit.

    Chris
  • @cbrandin Thanks for the detailed testing suggestions using a series of underexposed takes. This is similar to the procedure I used for evaluating shadow detail in the GH1 Max Latitude Patch, and it revealed things I wasn't expecting to see. For example, I started to notice the tendency for low-quality static macroblocks to appear in the bottom part of the frame in high-detail images. However, I couldn't make sense of it until I read your explanation of how the AVCHD encoder behaves when it runs out of bitrate before it reaches the end of a frame...
  • @stonebat The GH2's short-GOP behavior appears to be far more sensitive to patch parameters than it was on the GH1. The 3-frame GOP at 720p30 on the GH1 was an unexpected discovery - I had already concluded that GOP-lengths from 4-8 were unstable under stress. At 3-frames, the GH1 boosts its I-frame bitrate and suppresses the P-frames in a simple and predictable manner which produces excellent quality and good compression. The GH2 seems to be juggling more balls at once, attempting to balance I, P, and B-frame cadences for a longer GOP sequence, even when it's set to a 6-frame GOP. This appears to cause it to periodically allocate P-frame bitrate levels for one of the I-frames in each extended sequence of 6-frame GOP's.
  • Have we found a "best" 66mbs setting yet?
  • We're getting there - give it a couple of days...

    Chris
  • @cbrandin thanks, in the meantime i am shooting with:

    Version increment=1
    Video Bitrate 24H=66000000
    Video Bitrate 24L=35000000
    Auto Quantizer for 1080 modes=4 - All to details
    1080i50 and 1080p24 GOP Size=3
    1080p24 FB1=1566720
    1080p24 FB2=1968046
    1080p24 Frame Limit=15728640

    Unless somebody knows issues with this set up i am about to walk out the door! The only difference is i used to shoot x3 then no x, now testing 2x, wish i had more time for this stuff right now, but yea i'm real eager for the perfect 66mbs =) i'll let you know how the above goes.
  • Well... the GOP 3 might bite you. Vitaliy is working on a fix. I'd be inclined to avoid the low GOP stuff until he releases the next PTool.

    Chris
  • Ideal for close-ups and people in motion:
    in mind an ideal setting in AVCHD Intra (GOP1) before averaging 45MBit
  • @LPowell Exactly. Juggling more balls... and I guess it's a good thing.
  • @OSGondar There is no such thing as a best 66Mbps. It's like asking what is the best preset for Lightroom.

    Eventually we'd get a "range" of generally recommended settings as we understand enough characteristics of params over the range.
  • @Anpanman My setting... I keep changing mine... I don't wanna upload gozillions of setting zip files here.

    Just stay below 44Mbps. Default GOP or 12 GOP. Double the buffers. That's about it for now.
  • @stonebat "It's like asking what is the best preset for Lightroom." You are way off on that one. By now you may know what i mean by best if you ever bothered to read through threads rather than post a new one whining that you are not about to read that much, "give me answers".

    Best for me..... a 66mbs that gives enough information in the shadows to effectively give more dynamic range when i pull them in post whilst having under exposed to save as much highlight as possible. I do mostly narrative work but on occasion i am camera man / dp for documentary as well so for those situations based on having a lot more motion run and gun ill adjust for motion etc if i must but i think mainly what i mean is the most detail you can pull out of 66mbs shadows without artifacts. this the " image quality" thread right? how to handle Motion is up to the user to adjust etc but to say its like like asking for a Lightroom preset is akin to me asking you how to color correct my footage, far from it. A raw file is aquired BEFORE importing it right? right, so that's where i'm at, i dunno what the hell you think your going on about but for future reference i'm not addressing you when i post, but thanks i guess, for the useless reply. if you have nothing to contribute don't reply for the sake of sounding like a smart ass.

    @cbrandin I'm going to test my settings at gop 3, 6, 12 off etc. I read to avoid 3 for now, still i want to see what the effect is since i'm already out and about and i haven't seen any real footage comparing them, i have a shoot starting Monday and i really want to shoot at 66 because it still gives a good 1hr out of 32gig whilst a nice bump in birate / detail so i really hope to get it figured it out over the weekend. ie working settings or best image in 66mbs at moment, Thanks
  • sorry if i sounded rude to you. it's friday. tgif. i'm going out to drink and party.
  • @stonebat its alright, it did irk me but i had a long day of editing, my least favorite gig. I just really need to get closer to the work horse 66 because i am dp'ing a shoot a little too soon for comfort. I found little patience in the moment, i'm sorry as well. In any case its indeed Friday, enjoy
  • Try these two settings:

    GOP12 AQ3
    GOP6 AQ1

    It seems we have limited choice due to the cadence anomaly.

    Anyways. TGIF. Cheers to all of you the good people!!!
  • IMHO low GOP (3 or 6) lowers IQ with this version of PTool.
    First few seconds run fine (even with 110Mbits / GOP3) but there is said issue with the uneven cadence and I-Frames go down to 6Megabyte and below.

    Here are 2 settings that work for me fine so far (for 24p, 50i, 720p50 without B-frames). All GOP 12.
    I've started with the settings of "mpgxsvcd" and then tuned them step by step with regard to settings of other users posted here. I-frames are higher than 9 Megabyte in both settings and the cadence is even.

    Setting B:
    Video Bitrate 24H=66000000
    Video Bitrate 24L=32000000
    Video Bitrate FSH/SH=32000000
    Video Bitrate FH/H=24000000
    Auto Quantizer for 1080 modes=4 - All to details
    Auto Quantizer for 720 modes=1 - Some to details
    720p50 GOP Size=12
    720p60 GOP Size=12
    1080i50 and 1080p24 GOP Size=12
    1080i60 GOP Size=12
    1080p24 FB1=3133440
    1080p24 FB2=3936092
    1080p24 Frame Limit=31457280

    Setting C:
    Video Bitrate 24H=52000000
    Video Bitrate 24L=32000000
    Video Bitrate FSH/SH=32000000
    Video Bitrate FH/H=24000000
    Auto Quantizer for 1080 modes=4 - All to details
    Auto Quantizer for 720 modes=1 - Some to details
    720p50 GOP Size=12
    1080i50 and 1080p24 GOP Size=12
    1080p24 FB1=1566720
    1080p24 FB2=1968046
    1080p24 Frame Limit=15728640

    When you look at the screenshots of streamparser attached it's pretty clear that Setting B achieves larger P and B frames in the same scene.

    There is one issue, though, with the 24p MTS files from this settings... and this is a serious one.
    Avid won't import the 24p files (50i and 720p50 are okay). Clip Wrap does convert them but the files are trashed with weird artefacts (again this only goes for the 24p files).
    5DtoRGB and Neoscene convert the files just fine. Also VLC and EyeTV can play back the files.
    setb_streamparser.jpg
    1150 x 417 - 201K
    setc_streamparser.jpg
    1161 x 410 - 194K
    setb.zip
    404B
    setc.zip
    398B
  • Guys, I suggest to try not the low GOP, but the higher than normal GOP.
    I mean 2x of normal GOP.
  • @towi

    also with setting C have you problem with clip wrap?
  • "also with setting C have you problem with clip wrap?"
    yep

    "Media Converter" does the job, though.
    http://media-converter.sourceforge.net/index.html
    You can also simply re-wrap with Media Converter ... just use the preset attached.

    mc_rewrap.zip
    524B
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