Be careful using tripods. The GH1's ( and GH13's) Achilles heel!

[Lpowell]

The issue that I am talking about is a "pulsing" that happens at regular intervals throughout the footage. With the 60p footage it seems to be about every 30 frames.

The GH1 and GF1 standard 720p60 AVCHD mode uses a 30-frame GOP, with one key frame every half-second. If the codec lacks enough bitrate to fully encode a key frame, many of the details in that frame will turn muddy. In the 29 following P-frames, the codec will have many opportunities to improve the resolution with more finely-encoded details. If the key frames end up with significantly lower resolution than the P-frames, you'll see the video suddenly get blurry at a steady rate of two times a second. This 2fps rate would be readily perceptible as a "pulse".

The 40Mbps AVCHD High Reliability Patch retains the standard 30-frame GOP for 720p60 video mode. In my 50Mbps AVCHD Fast Action Patch, I was able to use a 3-frame GOP in 720p30 mode. Any pulses that may be produced with this 3-frame GOP would occur at a rate of 10fps, which is frequent enough that key frames would not be perceived as individual pulses.

 

[shaveblog]

Yes, you must have the older 24" Apple Cinema Displays, which are great in their own right. I may just end up picking up one of those if I can score one in little-used shape.

The new Apple 27" is perfect for my needs (love the built-in webcam and mic for Skype and Google Voice, etc.) except for two things, the glossy screen and the need for a video card with mini displayport, or another $100 for a DVI-mdp adapter. The idea of spending $100 on a little dongle with its own wall wart just to mate a monitor with my computer rubs me the wrong way.

Ultimately though I think the glossy screen is the deal breaker. I just don't like this kind of screen, especially on such a large real estate monitor as a 27". I'm too ugly to stare at my own mug all day. I put up with it on my iPad but I can't do it all day at my desk.

So, the Dell. I really dislike Dell and am not up for a round of returns till I get one without dead pixels or color issues, but I don't see anyone else doing a serious monitor with that gorgeous panel.

Sorry I use 2 of the older aluminium monitors, not the 27 inch new ones. I think they are 27" maybe less don't know. I use Color and FCP on my system and it is great over 3 monitors I also have a JVC LCD broadcast monitor at the side to see full res work as it will be broadcast.

I like the old ones because they are matte screens. I sound like a screen junky but I got my second one very cheaply as a refurb. I really don't have a lot of time for the new glossy monitors. They look fantastic but for actual work I'd say you need very low lighting to work seriously with them to minimise reflections.

 

[Shawn Storm]

Try changing your 60p GOP size in hack to something much lower, like 10 or maybe even less.
It defaults to 30, which is why every 30th frame is sharp.

Interesting! I haven't touched the GOP settings when applying any of the hacks (mostly because it hasn't been mentioned much in most of the settings posted on DVXUser). I can play with this, but I am wondering if people have already tested various GOP numbers? If so, can someone direct me to the appropriate thread(s)?

Thanks,
-Shawn-

 

[Lpowell]

...I am wondering if people have already tested various GOP numbers? If so, can someone direct me to the appropriate thread(s)?

Here's a link to my 50Mbps AVCHD Fast Action 3-Frame GOP Patch:

http://dvxuser.com/V6/showthread.php?t=222791

This patch produces 3-frame GOP's in 720p30 AVCHD video modes.

For 1080p24 FHD mode, PTool's GOP patch does not alter the GOP-length when Native 24p is not checked. Since no reliable Native 24p patches have been developed yet, I haven't activated Native 24p in any of my patches.

 

[reggietelly]

I did try the 3 GOP patch and it did look a lot like MJPEG compression. Yes there was noise but not to the same extent. In fact I could live with it. Deal breaker for me was that due to the hike in bitrate required you have to reduce 720p 50fps to 25 fps. That's one thing I really like about the camera, it's ability to do nice slo mo to 25fps from 50.

I also noted that this patch didn't change the GOP length of 1080p 25fps. Is there a safe level to go down to with FullHD footage or is this just not possible at the higher bitrates? Again like Shawn I haven't touched GOP settings as they are never mentioned in the patches.

 

[chrisso]

Sharper:

More Blurry:

-shawn-

I find it hard to see pulsing. However, what is always obvious to me in all your examples is that one grab is brighter than the comparable one.
I can't explain it, but the 'sharper' image is quite obviously to me darker than the 'blurry one. Same goes with the pics of the computer screen.
Frame 1 very noticeably darker than frame 30.

 

[Lpowell]

I also noted that this patch didn't change the GOP length of 1080p 25fps. Is there a safe level to go down to with FullHD footage or is this just not possible at the higher bitrates?

Sorry I may not have been clear about this misleading aspect of PTool. Even if you check the GOP patches for 1080p24 or 1080p25, they won't have any effect unless you have also checked the Native 24/25p patch as well.

And since the Native 24/25p patch produces corrupted video streams, there is currently no reliable way to alter the GOP-length of 1080p24 or 1080p25 videos.

 

[Shawn Storm]

I find it hard to see pulsing. However, what is always obvious to me in all your examples is that one grab is brighter than the comparable one.
I can't explain it, but the 'sharper' image is quite obviously to me darker than the 'blurry one. Same goes with the pics of the computer screen.
Frame 1 very noticeably darker than frame 30.

I watched the video very carefully and there doesn't seem to be a variation in darkness. I do see what you are saying when viewing the images in this forum, but I think it is because one is above the other (assuming you are viewing this on a LCD screen). I took the images on my computer and put them side to side and they look the same. Then I put them one on top of the other and whatever image is on top looks darker because of viewing angle on the LCD screen.

Regarding the pulsing - did you download the example .MOV files that I posted? It is fairly noticeable to me, but perhaps I am just super nitpicky?

-shawn-

 

[Shawn Storm]

RE: GOP Settings

RE: GOP Settings

Here's a link to my 50Mbps AVCHD Fast Action 3-Frame GOP Patch:

http://dvxuser.com/V6/showthread.php?t=222791

This patch produces 3-frame GOP's in 720p30 AVCHD video modes.

I will try doing some GOP experiments, but I am less drawn to 720p30 mode because I like the 60p for doing smooth slow motion and I wouldn't want to lose that.

I am assuming the patch you mention doesn't work with 60p?

I also like the patch I am currently using and am wondering if keeping it the same and just playing with the GOP would cause issues. Are there any standard GOP values that I should stick to?

I am somewhat unclear on how altering the GOP values affects things overall. I think I kind of get how the "Group of Pictures" thing works with P frames and I frames, but I don't fully understand it. I read that reducing the GOP makes compression less efficient, but does that just mean larger file sizes or does it also change the quality of the footage somehow?

Thanks for the insightful information. I am still somewhat of a novice and apologize for now having a better understanding of the specifics.

-shawn-

 

[Lpowell]

I will try doing some GOP experiments, but I am less drawn to 720p30 mode because I like the 60p for doing smooth slow motion and I wouldn't want to lose that.

I am assuming the patch you mention doesn't work with 60p?

I also like the patch I am currently using and am wondering if keeping it the same and just playing with the GOP would cause issues. Are there any standard GOP values that I should stick to?

Unfortunately, the GH1 doesn't allow us to mix both 720p60 and 720p30 AVCHD video modes in the same patch. I tweaked the 720p30 patch to produce the shortest reliable GOP to make scrubbing through the footage in an editor very fluid. This makes it a good choice for filming long, one-take event documentaries.

The extremely long 30-frame GOP in the standard 720p60 AVCHD mode produces very efficiently compressed files that are rather choppy for editing purposes. If you lower the GOP-length, the codec will produce key frames more frequently, which will increase the bitrate up to its maximum. Beyond that point, image quality will suffer from not having enough bitrate to encode so many key frames. I suspect this is what produces the pulsing effect that you and others have pointed out.

I have not yet found a reliable patch to reduce 720p60 GOP-length to values as short as 6 frames, which would be comparable to the 3-frame GOP used in my 720p30 patch. GOP-lengths longer than this may work without producing corrupted video recordings, but would not suppress the pulsing effect as well.

 

[Shawn Storm]

The extremely long 30-frame GOP in the standard 720p60 AVCHD mode produces very efficiently compressed files that are rather choppy for editing purposes. If you lower the GOP-length, the codec will produce key frames more frequently, which will increase the bitrate up to its maximum. Beyond that point, image quality will suffer from not having enough bitrate to encode so many key frames. I suspect this is what produces the pulsing effect that you and others have pointed out.

Thanks for the info. Just for clarity, are you saying that reducing the GOP will raise the average bitrate of footage? So if I applied your patch then would darker and less detailed scenes have a higher bitrate which I assume would mean less mud and better detail? Less choppy editing is probably great for professionals, but I don't personally care that much. I am mostly interested in increasing visual quality of the footage in both low detail and high details scenarios.

I finally read your post about the "Fast Action GOP Patch" and it was very informative. It sounds quite snazzy and I may let go of my need for smooth slow-mo and try it out. Honestly I rarely use my 60fps footage for slow-mo anyways, and I have actually been wishing there was a 720p30 option (in addition to the 720p60) since I use Final Cut Express which only deals with 30fps. I suppose if I want to have smooth slow-mo I can re-do the hack, but that sounds like a bit of pain.

So when I get a chance I will try out your 720p30 GOP patch and see how it works for me. Thanks for all the info and all your hard work testing!!

-Shawn-

 

[Lpowell]

Just for clarity, are you saying that reducing the GOP will raise the average bitrate of footage? So if I applied your patch then would darker and less detailed scenes have a higher bitrate which I assume would mean less mud and better detail?

Shorter GOP-length may produce an increase in AVCHD bitrate, but only if certain conditions are all met:

1. Available bitrate is not already maxed out.
2. Scene details and/or motion are complex enough to require additional bitrate.
3. Lens focus is sharp enough to require additional bitrate.
4. Scene illumination is bright enough to generate wide dynamics in tonal depth.

If any of the last three conditions are not met, the AVCHD encoder will automatically lower the bitrate and produce more tightly compressed files. It was, after all, designed to minimize file size rather than maximize image quality.

 

[chrisso]

I use Final Cut Express

It illustrates what I think is a big problem with the AVCHD codec and is further to the pulsing problem noted elsewhere.
So I am having a huge problem with AVCHD footage.

A caveat first up: I'm completely green when it comes to video. I understand virtually nothing of the workings of 'the hack', AVCHD and Final Cut.

OK.......
I successfully hacked my camera and chose the lpowell settings. My main aim was to end up with superior image quality using AVCHD mainly. I tried viewing and editing in FCE (latest version), but the footage I was viewing didn't seem quite right. I'm a Pal user and can drop my AVCHD files straight into Final Cut without using a pulldown plug-in like Neoscene.
So I dug around this site and through Google.
I found a lot of people were editing with Pro Res 422 in their FC sequencer settings. It's a compression codec that retains very good quality.
I also found FCE didn't offer Pro Res 422 in it's sequencer pre-sets, instead what I assume are lesser options such as 'Apple Intermediate Codec'.
I went out and bought Final Cut Studio.
Excuse me if the above is absolute bolony, as I admit I'm very new to all this. However, I'm gonna guess that in any case it's not advisable to assess the GH13 files in such a critical way when using such an uncritical package as FCE.

 

[reggietelly]

I am getting a teeny bit tired of people telling me to expose properly blah de blah. I use the histogram on the camera I have tried countless settings and my conclusions are these.

The GH1 in AVCHD mode has a very hard time when you give it too little light. Take a look at the 2 examples.

The first image shows the camera set to Nostalgic with standard ISO enchance on. The Histogram was white and the frame is exposed pretty well. For my taste however I feel the fence is a little hot and I would love to take it done a stop to try and save that hilight. But look at the grass in the foreground to the left. I pointed the camera directly at it, and in shadow this is under exposed at least 4-5 notches. By using a polariser I was able to knock the sky back a fair bit. But the grass in the foreground is blurry and muddy along with the tree to the right of frame. These areas are very under done exposure wise.

Now look at the frame below. By overexposing just a notch the grass is now sharp. No blurriness, I mean even shrinking the FullHD frame down you can see a marked difference. But would anyone say that this frame was correctly exposed. Of course not. It looks overexposed. The fence is hot as hell, the trees are over bright in the background. There's no way you can get that back at all. The only way to shoot this scene is perhaps to use a grad filter coupled with the polariser.

So please stop telling me to expose properly because for the life of me I am trying my hardest. I mean no disrespect to the more professional shooters out there. I am a mere novice but I like my photography and I work in television so I do know a little of what I am talking about.

Which is that you cannot underexpose even a smidge with the AVCHD codec without serious issues.

Rant over


all the best

Richard

P.S. The more I look at these frames the more it bugs the hell out of me.

 

[Shawn Storm]

Shorter GOP-length may produce an increase in AVCHD bitrate, but only if certain conditions are all met:

1. Available bitrate is not already maxed out.
2. Scene details and/or motion are complex enough to require additional bitrate.
3. Lens focus is sharp enough to require additional bitrate.
4. Scene illumination is bright enough to generate wide dynamics in tonal depth.

If any of the last three conditions are not met, the AVCHD encoder will automatically lower the bitrate and produce more efficiently compressed files. It was, after all, designed to minimize file size rather than maximize image quality.

Ok - got it. Thanks for that clarification! It would be great if there was a way to increase the overall average bitrate for both detailed and non-detailed scenes but it sounds like that hasn't been discovered yet and/or goes against the basic logic of the AVCHD codec.

So I am starting to realize that for 720p maximum quality footage in all situations I should probably stick to high bitrate MJPEG and stop expecting too much from AVCHD.

-Shawn-

 

[Shawn Storm]

I found a lot of people were editing with Pro Res 422 in their FC sequencer settings. It's a compression codec that retains very good quality.
I also found FCE didn't offer Pro Res 422 in it's sequencer pre-sets, instead what I assume are lesser options such as 'Apple Intermediate Codec'.
Excuse me if the above is absolute bolony, as I admit I'm very new to all this. However, I'm gonna guess that in any case it's not advisable to assess the GH13 files in such a critical way when using such an uncritical package as FCE.

You are correct that FCE transcodes to AIC. For some reason I assumed that FCP used the same process since I thought "Log and Transfer" was the same for both programs. So I wonder if my using FCE is actually limiting the quality of the footage because of the transcoding to AIC?? I would LOVE to have FCP, but have not been able to afford it (or obtain it in other ways).

If it is true that I should be using a better transcoding process, can anyone suggest a relatively low cost alternative to using Log&Transfer with FCE??

Thanks,
-Shawn-

 

[reggietelly]

You are correct that FCE transcodes to AIC. For some reason I assumed that FCP used the same process since I thought "Log and Transfer" was the same for both programs. So I wonder if my using FCE is actually limiting the quality of the footage because of the transcoding to AIC?? I would LOVE to have FCP, but have not been able to afford it (or obtain it in other ways).

If it is true that I should be using a better transcoding process, can anyone suggest a relatively low cost alternative to using Log&Transfer with FCE??

Thanks,
-Shawn-

The issue is happening before any transcoding occurs. Look at raw .mts files in VLC and you will see the problem. In VLC these blurry artefacts are over exageratted and in fact when you transcode some of these issues are muted. 5DtoRGB does a good job at cleaning up some of these problem areas.

 

[chrisso]

So I wonder if my using FCE is actually limiting the quality of the footage because of the transcoding to AIC??

I would assume so, but I'm way below most taking part in this discussion in terms of experience and knowledge.

 

[Lpowell]

The first image shows the camera set to Nostalgic with standard ISO enchance on... But the grass in the foreground is blurry and muddy along with the tree to the right of frame.

These images contain a huge amount detail in the foliage that the AVCHD codec must encode along with the shaddowed grass and tree. In addition, ISO Enhance may be using up additional bitrate on areas that are already adequately encoded, rather than using it in the places you'd prefer. There is likely not enough bitrate available to capture all the details in the image at the same level of quality.

By centering exposure levels on the background foliage, you indirectly tell the AVCHD codec which aspects of the image you want prioritized. Details in areas that are either blown out or underexposed are assumed to be less important. This is why the encoder blurs the shaded grass in the first image, and records it much more clearly in the second image.

The AVCHD encoder is not well optimized for still image capture. It has a strong affinity for sharp, well-defined edges and large, slowly-moving foreground objects.

 

[shaveblog]

Apple Intermediate Codec is a very good codec, and it's what Final Cut Express and iMovie 09 use to transcode AVCHD and MPEG during importing. But it is a lossy codec, meaning that theoretically some degradation is possible. Whether you see any or not after transcoding is another question. Some see it, most don't, and I've seen plenty of jaw-dropping HD that was shot in AVCHD, transcoded to AIC, and edited in iMovie.

Apple's ProRes codec is included in the more expensive Final Cut Suite. It is a lossless codec, meaning you don't lose any quality when transacting to ProRes and then editing in Final Cut Pro. It is generally agreed that ProRes is a higher quality codec than AIC, but that doesn't mean AIC is rubbish. It is quite good, and capable of professional grade results. But it's not lossless, and ProRes is, so if you have both installed, it's sort of pointless to choose AIC.

Interestingly, while iMovie doesn't come with ProRes and doesn't let you choose it for importing footage even if you have the codec anyway, iMovie will happily import ProRes video that has been transcoded in Final Cut Pro and let you edit it natively.

There have been heated discussions and denunciations of AIC, most notably by that Eugenia woman who gets so worked up about the codec's evil you'd think she was talking about Fisher-Price Pixelvision. But I don't think it's a bad codec, and as I've said I've seen video run through its wringer that was just stunning. Check out the videos at craigmod.com where he reviews the GF1. That's some of the best pre-hack GF1 video I've seen, and it all came from iMovie and AIC.