40Mbps AVCHD High Reliability Patch

lpowell said:
A question that's come up recently is whether the GOP-length of the 720p60 AVCHD mode in the Reliable In-Camera Playback Patch can be made any shorter. The standard 30-frame GOP in 720p60 mode records one key frame every half of a second. In my 50Mbps AVCHD Fast Action Patch, I was able to reduce its 720p30 AVCHD mode to a 3-frame GOP, with a key frame every tenth of a second.

Unfortunately, there's a reliability issue with short GOP-lengths in the AVCHD encoder. Under extremely dim illumination, video bitrate can fall below 5Mbps. If this condition persists for longer than about 7 seconds, the AVCHD encoder may terminate the recording, leaving a zero-length file. This malfunction can occur with any AVCHD patch that uses a reduced GOP-length, and the only way to guard against it is to make sure your subject is adequately lit at all times.

Since the Reliable In-Camera Playback Patch uses the standard 30-frame GOP in 720p60 mode, it is not afflicted with this problem, and will record without failure at any level of illumination.
Click to expand...

I just did some more test with the 40Mbps patch and 720/60p GOP set to 6 and then another at 10. I used my backyard bushes of death and found recording failures at 6 but 10 worked pretty good. Bitrate held steady on both 25sec clips right at 40. Will do more testing, but the video looked great. All I had to do on the failures was reload the battery to reboot the camera and it was good to go.
 
Bobomatic said:
I used my backyard bushes of death and found recording failures at 6 but 10 worked pretty good.
Click to expand...
The short GOP-length reliability problem does not occur when shooting highly detailed scenes at high bitrates. It only happens when illumination is so dim that the bitrate drops below 5Mbps. Try shooting with the lens cap on and see what happens...
 
lpowell said:
The short GOP-length reliability problem does not occur when shooting highly detailed scenes at high bitrates. It only happens when illumination is so dim that the bitrate drops below 5Mbps. Try shooting with the lens cap on and see what happens...
Click to expand...

Yup.. it failed at 10secs with the lens cap on. But now I'm kind of curious about the earlier failure outside... hmm, will have to try that again.
 
What is the best patch to use for 24p and the GH1

What is the best patch to use for 24p and the GH1

What is the best patch to use for 24p native? I know no settings are going to be perfect, but what are the "most" reliable?
 
Last edited:
With this patch, would low-light performance be better in either AVCHD or MJPEG? Or would they perform similarly?
 
It's difficult to maintain high AVCHD bitrates in low-light conditions. The MJPEG encoder will typically produce more detailed images, though they may also reveal more noise. I've gotten good noise reduction results with Neat Video.
 
lpowell said:
The patch simply increases the maximum bitrate to the highest I've found reliable. It will work with any Film setting, and I agree with the general consensus that Smooth with -2 settings produces the most gradable results. For incandescent lighting, I like the subtle sepia bias of Nostalgic with -2 settings.

For best grading latitude, the patch's 35Mbps MJPEG mode produces 4:2:2 color depth, whereas the AVCHD encoder only supports 4:2:0 color. In addition, the MJPEG encoder's average bitrate holds up better in low-light conditions than AVCHD.

Note that the 8-bit YCC resolution of both MJPEG and AVCHD encoders is best-case, whereas the 12-bit GRGB Bayer sensor resolution is not degraded by compression. With MJPEG and AVCHD, you will only get near-8-bit resolution under well-illuminated, high bitrate conditions. In less ideal situations, YCC resolution will be compressed down to as few bits as the encoder can manage.

As long as you transcode to a 4:2:2 format with a decent intraframe bitrate, you will lose no significant quality in the process.
Click to expand...

ipowell, can you clarify what Film mode settings you recommend for best grading latitude?

Also, thanks for clarifying the MJPEG versus AVCHD low-light performance. Would you recommend switching to MJPEG in low light and attempting noise reduction in post?
 
CColton said:
Would you recommend switching to MJPEG in low light and attempting noise reduction in post?
Click to expand...
I agree with the general consensus that Smooth Film Mode produces the best results for light grading. I set Contrast and Noise Reduction to -2, the rest to 0.

With a high bitrate, the MJPEG encoder can produce finer detailed images in low-light conditions than AVCHD. You may be interested to try my Fast Action 3-Frame GOP Patch for its 60Mbps MJPEG patch:

http://www.dvxuser.com/V6/showthread.php?222791-50Mbps-AVCHD-Fast-Action-3-Frame-GOP-Patch
 
Hey I have a mac and I can only find 3.40d with wine for mac. I can't seem to find 3.50. I went ahead and updated to these specs using 3.40d on my mac. this is the second setting change I've done so far. Will this be ok? I saw that there was a warning about only using 3.50. I really didn't see that until after I updated. I got too excited and only looked at the bitrate settings to change.

Should I encounter any problems?
 
I also use a Mac. If you go to the hack address at the beginning of this thread you should download 3.50 (unless something has changed since I was last there). Wine is a separate application to read the Windows files.
 
unfortunately not so reliable with my gh1

unfortunately not so reliable with my gh1

I tried it, but using class 6 and sandisk class 10 it halts recording under certain circumstances. I first noticed it when driving in a car, I pointed the camera straight ahead so the scene was constantly changing and it would say the card wasn't fast enough and stop after a few seconds. So then I bought a sandisk extreme class 10 30MB/s card and still did, though lasted a little longer. So then went through several iterations of speed decreases and found zooming the camera in and out quickly several times would cause it to give me the card speed error really quickly. So to see if it was a general issue, I reset back to defaults on all speeds and I couldn't get the error, so then ended up on 32Mbps FHD and 34Mbps overall and I am still able to get the error, but its much tougher. I still have to do the driving test to see if its at least fine that. So it appears my buffers get overrun pretty easily on my camera no matter what card I use if I crank the bitrate very high.
 
waqarch said:
is it possible to have 24p and 25p on a PAL camera. if yes. can u please explain how?
Click to expand...

I think you can't have 24p on a PAL camera. But just enable PAL <> NTSC switch with the hack. So you can have 25p in PAL mode and 24p in NTSC mode. But you have to use at least to sd cards, one for PAL and one for NTSC footage...
 
rawmeyn is correct, a correctly patched GH1 or GF1 can be switched between NTSC and PAL operation in the Setup menu. After doing so, it's best to be sure the setting sticks by switching the camera off and on again. Each SD card must be dedicated to either NTSC or PAL videos exclusively.

After confirming your settings, you may want to save them in one of the three Custom slots. This will allow you to switch instantly between custom NTSC and PAL modes without using the Setup menu.
 
lpowell said:
rawmeyn is correct, a correctly patched GH1 or GF1 can be switched between NTSC and PAL operation in the Setup menu. After doing so, it's best to be sure the setting sticks by switching the camera off and on again. Each SD card must be dedicated to either NTSC or PAL videos exclusively.

After confirming your settings, you may want to save them in one of the three Custom slots. This will allow you to switch instantly between custom NTSC and PAL modes without using the Setup menu.
Click to expand...

You can also apply one of those custom settings to the CUST. mode on the camera (on the dial just past creative movie mode). Then just switch between the modes to switch standards. I do something similar by having all of my low-light settings on CUST and normal settings on creative movie mode so that I can film inside at night, then walk out into the dark and just switch modes to switch all settings at once.
 
I'm having big problems using these ipowell settings at 720/50 and a 1/50 shutter speed, the bitrate takes a massive noise dive down below 4mbps frequently. The only way I can sort this out is to use 1/60 shutter speed, and that works fine, but of course I'd rather use 1/50 to avoid any possible flickering. Has anyone experienced this? Any advice?
 
JimNastics said:
I'm having big problems using these ipowell settings at 720/50 and a 1/50 shutter speed, the bitrate takes a massive noise dive down below 4mbps frequently.
Click to expand...
Sorry it took a while for me to test these conditions using PAL 720p50 settings. I tried to reproduce your results on a low light indoor scene and obtained decent bitrates even at very low levels of illumination. This was in SH mode 720p50, ISO 800, shutter at 1/50. Here's what Stream Parser reported:

f2.8: 16.6 Mbps
f4.0: 13.2 Mbps
f5.6: 10.4 Mbps
f8.0: 7.6 Mbps
 
In case anyone has problems switching between NTSC and PAL, there is a Video Out in the menu. You dont need to flash a different firmware. Just switch it to NTSC or PAL. Exit Menu, Shut down. When you restart, the video is switched.
 
You must log in or register to reply here.
Back
Top