I started to play around with ptools 3.65d in an attempt to develop a stable/reliable and good quality settings for GH2. In these RAW times I thought more than 40 or 48Mbps bitrate would be good for grading and highlight/shadows improvement in post. But I would like to keep things in a practical way for daily use, good recording time and no firmware changing.

In a previous topic of mine I found GOP3 solved the diagonal pattern aka rain problem when playing files on computer, so I started the tests with GOP3 for all recording options.

First test was with 128Mbps vs 64Mbps in 1080p 24p. I started with these values due to be similar to Cineform "High"datarate and also due to the recording time. With the camera on tripod indoors, at 3200 iso, in a detailed scene, both recordings showed a file with something about 56Mbps, so the AVCHD codec was not needing more than this. So I decided to keep these settings 24H = 128Mbps and 24L = 64Mbps, both GOP 3.

Then I started to strees the codec: I went outdoors and did some recordings with lots of camera movements and also indoors in detailed cenarios in high iso with lots of movement. Also shoots with camera steady to compare.

I found the bitrate increased, and the maximum I found in the files was something about 114Mbps, so even in more complex situations with movement and detailed images the AVCHD codec did not need more than 114Mbps to do it with GOP3 even if it had 128Mbps to use. It was just not using all available bitrate, maybe due to 1080p 24p GOP3 does not need more than this. GOP3 is very good quality because there is always a I frame besides each B frame, and B frames size increases when there is camera movement.

In my study reading the topics about Ptools patches here in P-V, I read something that said: if you have enough bitrate you do not need to worry about quantization. maybe because there will be enough bitrate for everything. so I started to think: if the codec was not using all the 128Mbps even in complex situations, and GOP3 being good quality, why should I use GOP 1 and why worry about quantization? So I did nothing about this in Ptools. I decided to keep myself in GOP 3 and 128Mbps maximum.

Also, I found the difference recording 24L = 64Mbps and 24H = 128Mbps both GOP3 was almost unoticeable. I just saw very little difference, just found by pixel peeper people in a pursuing behavior, when I paused the playback in a high camera movement shooting foliage. Without pausing it I could not tell the difference. And when the camera was steady, there was no difference to perceive because the codec was not stressed.

My conclusion is: for a daily use, 64Mbps GOP3 will be the best option because it gives one hour of footage in 32GB SDHC cards and it is great quality. With the camera on tripod, indoors at 3200 iso, I could see some difference in small letters on a bootle in a image comparison between 64Mbps and 40Mbps video. I can read that small words better with 64MBps.

I could not see difference in this same scene (camera on tripod, high iso, detailed scenario) when comparing 128Mbps to 64Mbps. The 128Mbps GOP3 gives half hour in 32GB cards and can be used in scenes with lots of details and movement together, the only situation it is really needed.

To compare things, the Cineform codec in HIGH setting uses a maximum of something between 120Mbps and 180Mbps when transcoding mts files to avi intra. Remember it is 10 bit 422, so it needs 1,67x more bitrate than 8 bit 420. It is something like 160Mbps in Cineform is similar to 96Mbps in AVCHD. And when you render in VirtualDub using the same Cineform HIGH settings it keeps around 70Mbps, so the 128/64Mbps GOP3 in GH2 hack is pretty equivalent to Cineform quality.

Now let's move to the 720p 60p tests:

I used 128Mbps for SH and 64Mbps for H, and started to play with GOP.

I used the GOP suggested in Ptools and some others, starting with GOP3 and than 6, 10, 12, 15, 20, 24, 30...

I only could get some amount of footage with the default GOP 30. the others always stop recording, and when they records some time, if you move the camera fast in foliage it stops. So I perceived the GOP 30 was the most stable for 720p 60p with 128/64Mbps, but there was recording stop after some small time or when camera moves fast.

Then I started to lower the bitrate to find the reliable settings. When I reached 48Mbps GOP30 for 720p 60p things worked flawless. No recording stops and great image quality. I found even in high movement and high detail scenes the bitrate was never more than 42,66Mbps. If you do some simple maths you will perceive the 48 to 42,66 ratio for 720p 60p is the same of 40 to 35.55 ratio, so 48Mbps GOP30 for 720p 60p and 40Mbps GOP24 for 720p 50p probably will be the sweet spot. See:

60 / 50 = 1,2

48 / 40 = 1,2

42,66 / 35,55 = 1,2

So, after all these tests my finds for best quality/reliability/recording time balance are:

24H = 128Mbps GOP3

24L = 64Mbps GOP3

SH = 48Mbps GOP30 for 60p and GOP24 for 50p

H = 40Mbps GOP30 for 60p and GOP24 for 50p

(The B or P frames size increases when there is camera movement and quality is good).

Auto Quantizer off for all (box not checked)

I enableb high iso up to 12800 and that's all.

(Nothing changed in the red "patches for testers" section)

I got no diagonal pattern (rain) yet, but needs to shoot more tests in different situations to be completely sure.

Let me know what do you all think, please test it and compare to other settings before saying things...