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GH2 Cake v2.3: reliability and spanning in 720p, HBR, 24p, and VMM at 2-2.5x stock bit rates
  • 609 Replies sorted by
  • AndySAndyS

    @balazer - I truly appreciate your comments. Tell me - Is the "2.3" download in the second post of this thread - is that the newest one which incorporates the "FlowMotion" influence? ie. The latest of the latest?

    And lastly, when you use it with 24p, what is the "average" bitrate usually? 45 Mbits or so?

  • duartixduartix

    @AndyS:

    "For example, 1 for I, 4 for P and 10 for B, i.e., P gets 4 times of weight over I and B 10 times."

    There might be another reasoning behind this. Don't forget that the stock GOP consisted of 8 B-frames, 3 P-frames and 1 I. I was under the impression that these GOP tables were simply used in the bitrate allocation mechanism and had nothing to do with the quantization, which is the parameter that really defines IQ for each type of frame.

  • AndySAndyS

    Thankyou, Balazer. I truly appreciate it. Tell me - Is the "2.3" download in the second post of this thread - is that the newest one which incorporates the "FlowMotion" influence? ie. The latest of the latest?

    And lastly, when you use it with 24p, what is the "average" bitrate usually? 45 Mbits or so?

  • balazerbalazer

    The reasoning is all fine. There's just a huge amount of subtlety in designing settings that goes way beyond any of this reasoning. I chose P-frames because the GH2 rate controller sets the P-frame and I-frame QPs in the same way. I chose a GOP length of 3 because I could get the bit rate higher that way and still ensure spanning. The increase in quality from using a higher bit rate more than made up for the loss in efficiency in using a shorter GOP, especially at higher ISO settings. At lower ISO settings, there might be no difference, or there might actually be an advantage to using a longer GOP. But the quality is already more than good enough at lower ISO settings.

    It's not to say that my approach is any better or worse than anyone else's. I had a set of priorities, and I made certain decisions that led me down a certain development path. What I have now works very well, and I'm not about to revisit those decisions given the huge testing effort that any change requires. There are better ways of improving my video than to endlessly tweak and test the encoder settings.

    It's kind of silly to talk about the merits of different technical approaches if you haven't actually tried the settings and compared the results. I think you'll find that my approach works very well for the vast majority of shooting situations.

  • AndySAndyS

    @Balazer - The reason I am asking is because I am about to start shooting a full feature film. I may use Cake 2.3 for it. But I would love to learn about this aspect first. Any comment on PVDOG's reasoning (below) for the way he did things?-

    "There are two facts about my comment on "same quality for I/P/B..."

    1) If you look at the ini file or PTool, you can see: Scaling for I/P/B and fallback all have the same value. Stock values are worse for P, B and fallback. So my patch ensures constant good frame quality for all GOP frames and always - no fallback. I learned this trick from LPowell's very new Flow Motion patch.

    This is also why I'm not interested in the AQ4 patch (All to detail), because it is long GOP with lots of P and B frames and I don''t know if it still uses the stock coarser scaling for P/B frames and fallback.

    2) If you look at the GOP tables (under GOP Related), you can see: the stock values for I is much lower than P and B, putting a lot more weight on the coarser P and B frames. For example, 1 for I, 4 for P and 10 for B, i.e., P gets 4 times of weight over I and B 10 times. My patch lowers those ratios to 2 and 1.5. This trick is recently discovered by Balazer in his Cake patch.

    We all know, I frames are the most important and they should take up more part into a GOP. More I frames mean larger file size and faster cards, but 32GB class-10 cards are extremely cheap now for only $17, can still give you 2 hours non-interrupted recording even after this patch!

    Basically my patch combines all the latest great discoveries by LPowell and Balazer together with my own tweaks, it should be the very best by far, for both GF2 and GH2."

    Please comment on this, Belazer?

  • balazerbalazer

    It's not the approach that I would take, but that's not to say it's bad. You can try it and compare.

  • AndySAndyS

    @Balazer - can you please comment on what PVDOG says about this? Here it is-

    "This patch is inspired by two GH2 patches: LPowell's Flow Motion and Balazer's Cake.

    The key features are:

    1) All I/P/B frames are the same quality. You know, Panasonic uses worse quality for P and B frames.

    2) Use GOP tables to control max average bitrate, much better than frame limit and fallback etc., for optimal quality and stability.

    3) GOP 6, I-B-B-P-B-B-I. I always feel 15/12 is way too long but 3 is too short and cannot take the advantage of B frames.

    4) Reliable 4GB file spanning.

    5) Video plays fine in camera.

    6) No compatibility issues with video editing software.

    Fully tested, no crash yet even under the extreme conditions such as fast panning from very dark to very detailed, very bright areas. Average bitrate is about 45Mbps, Class-4 works fine, but class-10 is recommended for reliable 4GB spanning.

    Attached setc.ini has been fully tested, not a single failure; sete.ini has some small changes for more standard 90/72 GOP length, should be even more stable.

    Image quality and motion smoothness are simply superb, incredible for a $200 camera, I've never seen such sharp video..."

    What are your thoughts on this, Balazar?

  • balazerbalazer

    I made the decision to use P-frames and not B-frames because it gave me high reliability in all modes and the behavior of the rate controller that I wanted, with only a slight reduction in efficiency. I wasn't getting the same behavior from the rate controller with B-frames.

  • AndySAndyS

    @balazer - Are you familiar with the "b-frames" work of 'pvdog'? Pvdog claims that if he combines your Cake 2.3 with better b-frames (taken from FlowMotion) he gets the best of all worlds. His "pvdog" patch has been tested a lot on GF2 and also GF3. I have used it on GF2 - very nice. Does Cake 2.3 now take all this into account about "FlowMotion-type" B-frames? Would love to use it on GH2 if it does.

    I look forward to your reply.

  • duartixduartix

    @emynach : Sorry for leading you off on P-Frames, but since the scaling values for P-Frames was defined in the settings, I assumed it was different from stock.

    @balazer: Thanks for clearing that up.

  • balazerbalazer

    I-frames and P-frames use the stock I-frame scaling values. Fallback mode uses the B-frame scaling values.

  • duartixduartix

    @emynach The I/B frames scaling matrices have stock values but B frames aren't used in Cake IIRC. The P frames have non-stock matrices and there is scaling fallback defined for all modes. This is what I could gather looking at the settings definition, but @balazer can tell you more.

  • emynachemynach

    Hi, what is the matrix being used in cake 2.3? is this the stock matrix?

  • meemee

    @balazer, these belong here.

    using Cake v2.3 GH2 and Voightlander 17.5mm lens.

    Thanks to driftwood for helping me figure out which patch I had used.

  • emynachemynach

    Thank you Balazer. I have to say you have done an amazing job with this hack.

  • balazerbalazer

    It is safe.

  • emynachemynach

    ok, thanks, and it's safe to use this mode right? it's not overloading the camera or something like this ( i don't now much about how it works... maybe it's a silly question but i just want to be sure)...

  • balazerbalazer

    Yes, it is normal. Screen updates in 720/60p are slow, but the camera itself responds normally to your button presses and rotation of the thumb wheel and focus ring.

  • emynachemynach

    i've been using the cake v2.3 and it's really good, just one thing to make sure, when using the 720/60p mode in manual mode, changing the shutter speed while recording takes about a second for the info on the screen to update, also when using the manual focus while recording the focus bar updates slowly then the focus itself... as if the system is heavy loaded, is this normal with the hack?

  • tetakpataktetakpatak

    @FilmCat
    The bitrate is variable in this patch and that is good. Mount some sharp lens and shoot well-lit scene with many details in focus and you'll see how the bitrate is boosting. This patch is really excellent, balazer did great work here using the best of GH2's potential while keeping it stable and just always spanning on the 64GB Sandisk Extreme card.

  • FilmCatFilmCat

    Thank you, I just wasn't sure whether I'd done sonething wrong but that's great.

    Thanks for your help, Max.

  • balazerbalazer

    The file looks as expected. The quality is high. (QPs all around 18) The bit rate is low because there is very low detail. It's mostly out of focus.

  • FilmCatFilmCat

    Thanks for the quick response, I think there might have been quite a lot of white as the image was slightly over exposed, the scenes were also fairly simple but were movement heavy that is what it said in explorer and I did a calculation to confirm (filesize/length*8).

    I tried installing the patch twice, but I've constantly had bitrates far from 66Mbps. Although I am happy with the quality I was wondering if it was still below what is possible, as I said it's new so I don't have much knowledge of what improvement I should be seeing.

    I've included a link to one of the videos I shot today.

    http://www.gridlockmedia.co.uk/00002.MTS (00:20/71.8MB)

    Thanks again, Max.

  • balazerbalazer

    In 24H mode, Cake yields around 60 Mbps typically. You'll get a lower bit rate if significant portions of the image are all black or white or with very low detail. I don't know how you measured the bit rate, but I suggest using VLC. If you're not getting what you expect, redo your patching with PTool to make sure it is correct. Make sure you don't load any other saved settings or check any boxes before you load the Cake .ini settings. Also, reset the camera in Menu, Settings, Reset.

  • FilmCatFilmCat

    Hi, This is the first time I've applied any hack to my newly bought GH2 and I've just been doing a few shots but when I view the videos on my PC it says that they have a bitrate of between 25 and 40 Mbps. Is this what should be happening, or could there be a problem as I was under the impression that Cake 2.3 in 24H was 66Mbps.

    I'm using a Transcend class 10 card.

    Thanks for any help, I'm really looking forward to using the camera when the weather improves, It was a Christmas present :)

    Max.

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