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View Full Version : Will 24 Mbps make a difference?



weaselander
06-08-2009, 08:59 PM
Please keep in mind that I am an Engineer by training who is looking to buy a GH1.

It seems to me like this MUD problem is due to the high compression ratio when shooting at 1080P with only 17Mbps. Some have mentioned that 24 Mbps will help, and I sure it will, but to what degree? This change would allow the transfer of ~40% more information, but I don't know how that translates into real world results.

However, users have said that the 720P has far less mud and the camera allows you to shoot in 13Mbps, or a roughly 30% lower transfer speed. So if someone could take similar footage with both the 13 and 17Mbps in 720P and compare the mud, I think we could get a pretty good idea at the level of improvement if Panasonic gave us 24Mbps for 1080P.

What do you think?

Cassius
06-08-2009, 09:54 PM
The number of pixels has a lot to do with how the codec responds from what I understand, so I don't think treating it by percentage works. Another thing to keep in mind is that some people have said it may relate to the transfer speed with the memory device, though I'm not sure how much faith to put in that statement. Seems unlikely to me, but if that's the case it's even less a matter of compression issues. Someone with more knowledge on the codec in question could probably provide a much better response.

commanderspike
06-08-2009, 10:58 PM
Nah, I don't think it's to do with memory bandwidth or write speeds either. As someone else pointed out earlier, 17Mbps works out at 2MB write speeds - I have a 30MB write speed Sandisk (peak write speed that is) and still get mud.

I think it's to do with the lack of B frames, an encoding issue pure and simple.

squig
06-08-2009, 11:04 PM
1080 is 2.5x the amount of pixels/data than 720 squeezed into the same 17Mbps data stream.

Martti Ekstrand
06-09-2009, 12:36 AM
You are forgetting that the 720 AVCHD mode run at twice the frame rate or actually a bit more in the NTSC model.

squig
06-09-2009, 01:28 AM
yeah I did, right now I'm trying to forget about it altogether.

Barry_Green
06-09-2009, 02:11 AM
Guys, HMC150 footage looks *fantastic* in PH mode, and HMC70 footage looks really, really good at 13mbps. It's not so much the megabits, as it is the lack of b-frames that seems to be impairing the efficiency. More megabits will help, but basically this thing needs a proper fully-implemented codec chip like the HMC150 has.

commanderspike
06-09-2009, 02:57 AM
I wonder what the reasons are for the GH1's woes?

Is it the codec implementation in software? They didn't have time to complete all the features?

Is it the codec chip? If so, why did Panasonic do this, knowing it would cripple their flagship in this way.

Or is it to do with the design of the sensor? It's a pretty different system from that found in a dedicated video camera, for sure.

I doubt they can just drag and drop software & hardware implementations designed for video cameras into the GH1. Give them time and hopefully the GH1 will be a more complete article come August.

SLoNiCK
06-09-2009, 03:04 AM
What is "mud" in our case? It's a sign of total overcompression. Some blocks are compressed too strong so they totally loose their texture while neighbor blocks can still have some details. It looks like raindrops on watercolor painting.

Will thicker bitrate make the situation better? Of course! CABAC, b-frames are the tricks that will help, too. But they are not universal. Why? Cause they are the methods for finding more redundancy in video stream. When there _are_ some redundancy in video they will surely save some bitrate for complicated parts. But if video is noisy, shaky, flashy and crappy then camera coder will have to create redundancy by itself - blurring and washing out video. Thick bitrate is the best way to prevent it.

ROne
06-09-2009, 03:05 AM
I got mine this morning (PAL), I reckon VBR doesn't help.

No full tests yet!

Jackson Miller
06-09-2009, 03:31 AM
What are B frames, and are they not something that could be added with a firmware update? It's a hardware problem?

ryansheffer
06-09-2009, 05:45 AM
I am pretty confident 24mbps will do nothing. I've seen 9mbps avchd that looks great and doesn't break up nearly as much. My canon Xh-a1 even though 25mbps never breaks up like that and is using mpeg2.

DonalDuc
06-09-2009, 06:22 AM
For my Canon SX1 I'm using cheapest SDHC Class6 cards - and all are fast enough.

SX1 makes 43 Mbps (!) H264 - same like Canon 5DMkII - with 1920x1080. This are 5.4 MBps - EACH Class6 (guaranteed 6 MBps) are enough!

If someone has to much money: buy a new Class10 card :beer:

http://666kb.com/i/b9njq7pwz88m615yw.jpg

Rakesh Jacob
06-09-2009, 06:57 AM
I am pretty confident 24mbps will do nothing. I've seen 9mbps avchd that looks great and doesn't break up nearly as much.

Totally co-sign that. Clips from other cams I've seen/used @ 17mbps and less don't have issues @ 1080 that the GH1 seems to exhibit :(

I'm still getting a couple for a web series cause I think the 720-60p is plenty good and I can slomo anytime I feel like.
Hopefully Panny will address the 1080 issues for you guys that need it :beer:

Daniel L.
06-09-2009, 07:58 AM
Edit.. Well at first I said that I disagreed with Barry, but I think we are saying the same thing.


The 5D lacks B-frames too and does not demonstrate the same problems. Allow me to explain what I believe is happening:

When you pan your GH1 a lot is changing in frame all at once. Therefore, each frame now must carry much more information to keep up the integrity of the picture. Using B-frames you can reconstruct data based on algorithms. With B-frames you have more information using the same bit rate.

Since the GH1 has no B-frames, you don't have that extra headroom. So our problem is that we are not packing enough data into the signal, how do we get more? By bumping up the bit rate! This is exactly what the 5D does, and the signal is flawless. Well.. relatively speaking :)

--

This is really all speculation.... It's a lot more complicated than it appears. The problem can really be a combination of factors, and possibly not even related to bit rate at all! We have no way to tell how the GH1 h.264 implementation works.

Personally, I'm convinced it's a hardware limitation. There is only so much you can fit into such a small and inexpensive body. The camera is a fraction of what the 5D costs, and you are really paying up for the extra horsepower & electronics in the Canon camera. Based on specifications it's a much faster system which makes video more robust.

This leaves a GH1 firmware update less likely but still possible. There may be something they can do as far as increasing the efficiency of the system. Just a little bit of improvement could make all the difference.

Daniel L.
06-09-2009, 08:42 AM
Just wanted to add that the lack of B-frames is not necessarily a bad thing. In fact, for our purpose it can be quite good.

This really comes down to fundamentals. The h.264 codec was designed to be a delivery format. This is bad for us, delivery formats are heavily compressed and optimized for small file sizes while keeping up a detailed signal. Trouble is, this destroys much of the information we need to do proper color work, keying, etc...

B-frames are used to reduce the amount of actual data packed into the signal and increase the compression ratio. By not including B-frames you reduce the compression ratio, thus getting a better source.

Using math to reconstruct information with B-frames is much less accurate than the original source from the sensor. By not including B-frames you depend less on the math predicting data and more on factual image data.

At least, if you have high enough bandwidth to get it across...

paulgandersman
06-09-2009, 08:48 AM
I got mine this morning (PAL), I reckon VBR doesn't help.

No full tests yet!

when did you order and from where?

Nitsuj
06-09-2009, 08:49 AM
If they lock it down to 17Mbps and get rid of the VBR then I think it will help. From my understanding the VBR has it averaging around 8-10Mbps - I assume on the fast pans people are doing this drops down to compensate for sustained write speeds and we get the results some people are getting. But this is only in 1080p mode from what I understand as well. So if you are going to do a fast pan then drop down to 720p.

Psynema
06-09-2009, 01:45 PM
so you're all saying get a mark ii instead ? :Drogar-Dum(DBG):

Martti Ekstrand
06-09-2009, 03:11 PM
If they lock it down to 17Mbps and get rid of the VBR then I think it will help. From my understanding the VBR has it averaging around 8-10Mbps - I assume on the fast pans people are doing this drops down to compensate for sustained write speeds and we get the results some people are getting.
This is actually the reverse of how Variable BitRate works. It's main purpose is not keep sustained write speeds but to conserve file size. A VBR encoding drops down the bitrate when image content is simple - like a rose against a clear blue sky - and ups the bitrate when you tilt down on a field full of roses. I doubt VBR is causing the 'mud'.

Read about VBR here: http://en.wikipedia.org/wiki/Variable_bitrate and about H.264/AVC in specific here: http://www.drunkenblog.com/drunkenblog-archives/000312.html (scroll down a long way for tech info)

To very very shortly answer what B-frames are; they 'predict' coming changes in the image which increase quality without adding much to file size. However they also add CPU cycles to the encoding process so leaving them out in GH1 might be dictated by hardware limitations as several have suggested already.
On the other hand by upping the bitrate it might be possible to decrease the intervals between I-frames (the 'whole' frames in the stream) thus maybe making 'mud' less likely to occur. Tweaking interframe compression for optimum file size and image quality is a mix between tech know-how, art and voodoo so saying exactly what Panasonic should/could do to reduce mud is impossible for us outsiders.

Side note; some people has made a art form out of breaking interframe compression aka "data moshing". Example: http://www.youtube.com/watch?v=ZMZu0FO8G8U&fmt=18

DrBlaz
06-09-2009, 06:04 PM
sure there is something strange with this cam, I think is just panasonic crippling the camera, the lack of HDMI and the 30fps mjpeg even in PAL version point to that direction, if you want 24p just pay more.



The GH1 encoder *seems to* use the lowest h.264 profile the "baseline", so it does not use B frames , this is the frame structure:


1080p24 : I frame every 15 P frames

IPPPPPPPPPPPPPPPI


720p60 : I every 30 P frames

IPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPI


1080p25 : I every 13 P frames

IPPPPPPPPPPPPPI


720p50 : I every 26 P frames

IPPPPPPPPPPPPPPPPPPPPPPPPPPI



However, the mud appear in GH1, but not in other AVCHD cameras using similar bitrates or even less . Other cams like canon ,sony, and panasonic SD-H1, HDC-HS9,HDC-SD9, or even the panasonic HDC-SD1 from 2006! , all of them use B frames ,this is the frame structure:


-panasonic SD1, from 2006, I frame every 15 B and P frames:

IBBPBBPBBPBBPBBI

-canon HG10, I frame every 12 frames at 24p:

IBBPBBPBBPBBI

-sony XR250,

IBBPBPBPBPBPBPBI



And incredibly, the Panasonic Lumix DMC-TZ7, a Point&Shot photo cam, also don't use B frames, but uses a better encoder structure than GH1:

720p25:

IPPPPPPPPPPPPPI

this is I frames every 13 P frames, while GH1 in 720p uses I frames every 26 P frames.And... 17mbps,the same as GH1. even worse: the same bitrate is for 25p, not 50p, so the 17mbps only encode 25 frames,this is:


average bitrate average I frames size average P frames size
GH1 720p50 15.2mbps 100kb 30kb
TZ7 720p25 15.4mbps 200kb 60kb

the above values are from the GH1 review videos on dpreview and a couple of mts from tz7 I found. Of course using double P frames could be due to the too low bitrate for encoding 60p.


if panasonic crippled the encoder deliberatedly, a firmare update is not likely to happen... so let's start HACKING!

Zack Birlew
06-09-2009, 06:35 PM
From what I've been reading both the GH1 and 5D Mark II suck as video cameras and it all boils down to the codecs used. Me, I don't care too much because I've worked with an HV20 and Nikon D90, both labeled as "Useless" because of jello wobble. Well, the solution is to simply not move the camera while filming and, thankfully, that's how I film anyway. On the same point, the GH1 and 5D Mark II don't exhibit codec problems ALL the time. I've seen examples of when they do now and, whoo-boy, that's some gnarly breakup. Would I not buy either one because of these problems? No. I could use the 5D Mark II and GH1 equally, both offer me something over my Nikon D90, especially the GH1's lens choice capability and the 5D Mark II's low light performance. Having worked around the Nikon D90 and Canon HV20 issues, the codec issue, to me, is just something else I'd have to work around or avoid while I work to make some really beautiful footage.

Boz
06-09-2009, 09:18 PM
sure there is something strange with this cam, I think is just panasonic crippling the camera, the lack of HDMI and the 30fps mjpeg even in PAL version point to that direction, if you want 24p just pay more.



The GH1 encoder *seems to* use the lowest h.264 profile the "baseline", so it does not use B frames , this is the frame structure:

*snip*

Thanks for the detailed layout of how the GH1 encoding works (or is it, doesn't work?)



And incredibly, the Panasonic Lumix DMC-TZ7, a Point&Shot photo cam, also don't use B frames, but uses a better encoder structure than GH1:

720p25:
IPPPPPPPPPPPPPI

this is I frames every 13 P frames, while GH1 in 720p uses I frames every 26 P frames.And... 17mbps,the same as GH1. even worse: the same bitrate is for 25p, not 50p, so the 17mbps only encode 25 frames,this is:

average bitrate average I frames size average P frames size
GH1 720p50 15.2mbps 100kb 30kb
TZ7 720p25 15.4mbps 200kb 60kb

the above values are from the GH1 review videos on dpreview and a couple of mts from tz7 I found. Of course using double P frames could be due to the too low bitrate for encoding 60p.This explains a lot as to why the TZ7 video looks so good while the GH1 is so lacking. And both cameras are from the camera division of Panasonic! *Sigh*



if panasonic crippled the encoder deliberatedly, a firmare update is not likely to happen... so let's start HACKING!I don't believe they deliberately crippled the encoder; they've said they set it at 17mbps to ensure playback on DVDs or something to that effect. They either need really up the bandwidth like the 5Dii & K7, which I don't think they can do since AVCHD has a 24mbps cap (I don't think 24mbps will make that much of a difference), or they at least have to give us 24P in MJPEG mode. If they enable 24mbps AND eliminate the 60i wrapper that might be enough (barely) to make a difference.

Daniel L.
06-09-2009, 09:45 PM
1080p24 : I frame every 15 P frames

IPPPPPPPPPPPPPPPI

That's an identical structure to the 5D. Difference is 1080p30 at 42 Mbps (VBR).

commanderspike
06-09-2009, 10:38 PM
Great thread.

The comparison between the GH1 and TZ7 encoding is especially interesting. The larger gap between I frames on the GH1 must be because of efficiency or bandwidth reasons because the 1080 24p mode has a lot more pixels, keeps a lot more detail and a lot more dynamic range than what the small sensor in the TZ7 is capable of.

From what I know, the TZ7 has a single image processing unit, the GH1 has two (or at least some kind of dual core CPU).

So I don't think they crippled the hardware.

So that makes me lean towards the awful conspiracy theory - they crippled the GH1 to put off pros, and thus protecting their margins on the pro equipment over at the dedicated camcorder division.

But I find that a strange strategy.

Canon didn't feel the need to cripple the 5DMII. I don't think they didn't have time to sort out AVCHD encoding and the 30fps is due to the limitations of the encoding format used in the 5DMII. Not crippled.

So I don't think the GH1 is crippled either... it just doesn't make sense.

Some great work here but I think until we have a Panasonic engineer on here I doubt we'll have anything more than conspiracy theories.

As for a hack, the GH1 isn't even in most people's hands yet in Europe or the US, so I think a hack is a long long way off yet.

ryansheffer
06-09-2009, 11:09 PM
@Jack_Felis
Not sure if you've used the 5d but the codec is incredible. I have worked with nearly all HD formats and H.264, though needing to be converted, is a fantastic format.

I have tried to tear up the 5d codec in many different ways without success. With that being said the rolling shutter is DEFINITELY present. But in terms of codec quality, the 5d handily beats nearly all cameras I have used. One in particular that it blows out of the water is ex1/3 xdcam footage.

killacam
06-09-2009, 11:43 PM
Personally, I'm convinced it's a hardware limitation. There is only so much you can fit into such a small and inexpensive body. The camera is a fraction of what the 5D costs, and you are really paying up for the extra horsepower & electronics in the Canon camera. Based on specifications it's a much faster system which makes video more robust.

I'm not sure if it's a hardware limitation, at least as far as the processor. There really isn't much reason to believe the Venus Engine V is any less powerful than the Digic 4 in the Canon. The Digic 4 is just a consumer chip also used in the cheaper compact Powershots.

There's a possibility there's also an H.264 hardware encoder/decoder chip in these cameras but who knows. The main difference is probably just in how the codecs are implemented and the bitrate. I do think increasing it to 24mbps should help.

Daniel L.
06-10-2009, 12:16 AM
It does not really mater which camera is faster.

Seems to me like there are 2 solutions to this problem.
1) Add B-frames
2) Bump up the bitrate

Both of these will have the same result, increasing the bandwidth and allowing for a much more robust video feature. Both of them will require more system resources. The question is if there are enough free system resources on the GH1 body to allow this, and if Panasonic is motivated enough to do something.

This is more speculation, but I'm guessing the reason there is no live HDMI on the GH1 while recording is because the system is stressed during encoding. We see a similar thing on the 5D where the live video is reduced to 480p. In this case, there may be nothing anybody can do.

Martti Ekstrand
06-10-2009, 12:30 AM
DrBlaz: A not so instantly obvious effect of interframe compressions is that the higher frame rate one uses the less info each P frame needs due to less change in-between them but that the I frame have less data than the TZ1 is indeed odd. That said I have the TZ1 and though a very nice little camera it doesn't match the image quality that the GH1 can produce in video clips, the feel is more low-res and softer just like small chip camcorders (although it spanks my old Sony VX1000 six ways to Sunday at a tenth of the price, ahh the sweet stink of progress).

When we talk about hardware limitations lets not forget that the major task VDSLRs have is real-time rescaling from the large sensor which is something that encoding process has to be balanced against. That the GH1 encoding could use some better tweaking is in no doubt - question is if it's doable.

As for crippling I suspect it's the opposite, GH1 video mode started out aiming for a solid 720 following Nikon's D90 lead then Canon uses 1080 in 5D and the Panasonic Plasma division wonders why the cam isn't "FullHD" and viola, a 1080 mode is crammed in and to explain that the data rate isn't doubled they make it 24p - "hey just like movies".

The firmware update we really should convince Panasonic to do is enabling FullHD 30/25/24 HDMI out when the cam is not recording for... ahem... 'checking focus and exposure' and then not tell them that we will never press the cam's recording button but the one on our external recorder.

BrianMurphy
06-11-2009, 06:39 AM
I find it amazing that so many people are basing their opinion of the GH1 on other peoples experiences. This is first a consumer still camera. How many of the motion picture issues that are being bantered around here can be resolved or chalked up to bad decisions on the part of the operator or using the wrong tool for the job? Many. I find it amazing that people expect to get everything built into a camera that costs less than $2k. Several Pros have shown what it is capable of doing when "Operated Correctly" under the right conditions.
Some of what I read here is just plain nonsense. I don't have mine yet, like many here I am due to get it in the next few days, but I will be away for two weeks on a shoot, so it will have to wait. But I bought mine for specific purposes based on Hunter, Kholi and Phil Bloom's reports and assessment of the camera. Not as the general all purpose do all camera. I don't know of any camera that falls into that class.
I am not saying that there is no merit to the questions regarding its range and possible upgrades. But conspiracy theories and flaming from people who haven't even touched a camera is just plain dumb. I have decided to no longer read these threads but rather find threads that have footage and comments from people actually using the camera.

Coco Bermudez
06-11-2009, 07:26 AM
I don't have mine yet, like many here I am due to get it in the next few days, but I will be away for two weeks on a shoot, so it will have to wait.

I am patiently waiting for others to get their cameras so we can all start to troubleshoot the basic flaws this camera has...either because of operator error or camera shortcomings. All I know is that I have tested mine ever since I got it last Friday and I am encountering several "concerning" issues.


I bought mine for specific purposes based on Hunter, Kholi and Phil Bloom's reports and assessment of the camera. Not as the general all purpose do all camera. I don't know of any camera that falls into that class.

I also bought this camera based on the footage and opinions posted by Hunter, Kholi and Phil Bloom...I do not regret it...form me personally, the camera is not there yet and I hope that Panasonic will be able to correct the basic features that seem to be flawed. I don't think that the issues are that horrible..a little tweak here and there...just the basics to make this camera fully functional


I am not saying that there is no merit to the questions regarding its range and possible upgrades. But conspiracy theories and flaming from people who haven't even touched a camera is just plain dumb.

right on...you can't make wild speculations about the camera if you do not have it...on the same note, you can't ( and I don't mean you Brian) go off on the people who have the cameras and are reporting the issues questioning their technical abilities...I say, let's wait and see what happens when we all have the GH1 in our hands.


I have decided to no longer read these threads but rather find threads that have footage and comments from people actually using the camera.

my advice...just read the posts and be prepared for issues...it will make the headache less severe! :)

Osslund
06-12-2009, 01:59 AM
I guess we never will be satisfied ;)

From my perspective, when I bought the D90 it seamed to be a perfect stillcam and videocam. It still is an excellent stillcam, but the video feature is so underdeveloped.

I can get really good images in daylight with the D90 but there are so many things bad with it. The GH1 in 720 rez seams to be a no brainer for the price. Just wait for the body-only and put on the great Nikkkors on the GH1. But it can't compete with the D90 as a stillcam.

And then theres the 5DmkII. Great stillcam but 30fps for PAL just don't do it for me. If the 5D would come with 25 or 50 fps I would sell all my Nikon and go for Canon. This would be a no brainer. Great stillcam and great videocam.

So to conclude. The GH1 wont cut it a stillcam but could be made to be a very decent and useful videocam. With a little tweaking of firmware.

Moneywise, glass will always be the most expensive thing and the thing that impacts the most in the final image. And I'm really torn between bodys here.

Let's keep our fingers crossed for firmware updates from Panny. My LX3 has had 3 upgrades since last fall so it seams resonable expecting the same for the GH1.
(So has also my Panny BluRay player been treated with firmwares)