Author Topic: EOS M: GOP, BITRATE, FLUSH RATE settings for H264  (Read 1183 times)

SoccerTeaz

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EOS M: GOP, BITRATE, FLUSH RATE settings for H264
« on: February 21, 2014, 10:59:16 AM »
There is already a guide for the 600D specifying the best GOP, SLICE, etc. settings for doing H264 with and without audio.

Can anyone offer similar advice on settings for the EOS-M ?
Keep in mind, the goal is specifically to use Tragic Lantern to get the most out of H264 video (recommendations for when audio is needed, and for when it is not)?
Any advice would be appreciated; I'm not even sure if bitrate effects H264 video, so a bit in the dark here.
Thanks   :)

tupp

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Re: EOS M: GOP, BITRATE, FLUSH RATE settings for H264
« Reply #1 on: February 21, 2014, 10:03:33 PM »
The best GOP setting would be "1," as that setting eliminates inter-frame compression and its artifacts.  Some folks report good results with a GOP of 3 (inter-frame compression across two out of every three frames), and that setting allows a little more boosting of the bit rate.

In either case, the bit rate can probably be set to CBR 2.5 with a fast card and a fairly complex scene.

Perhaps someone else can chime-in on ideal slice settings, etc.

gary2013

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Re: EOS M: GOP, BITRATE, FLUSH RATE settings for H264
« Reply #2 on: February 22, 2014, 12:00:10 AM »
The best GOP setting would be "1," as that setting eliminates inter-frame compression and its artifacts.  Some folks report good results with a GOP of 3 (inter-frame compression across two out of every three frames), and that setting allows a little more boosting of the bit rate.

In either case, the bit rate can probably be set to CBR 2.5 with a fast card and a fairly complex scene.

Perhaps someone else can chime-in on ideal slice settings, etc.
I have the M camera. I just did some testing of various settings shooting H264. I am shooting 1080p30 with audio on. F2.0, 1/64 shutter and iso 800. I managed to get CBR 10.0x, flush rate 30 and gop 1. I was surprised, but i never tried the flush rate that high. it might even go lower, but a flush rate 10 was crashing no matter what CBR setting I used. I also have a Sandisk 32gb, 45mb/s  write.   A faster card will be of no use on this camera since the internal hardware cannot write above an average 36mb/s. I was also getting bitrate readings around 30 for A and B. In the past I was able to get up to 115 bitrate readings with certain CBR settings.   
This was all done using the latest TL build from today. 

Edit, I just shot with the CBR at 20.0 and it still worked. Is this good? I don't know.

SoccerTeaz

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Re: EOS M: GOP, BITRATE, FLUSH RATE settings for H264
« Reply #3 on: February 22, 2014, 02:07:11 AM »
Thanks so much for the info!!
I'll give it all a try.  I had no idea one could (safely) set the bitrate that high.
I think the problem i was having was a misunderstanding of Flush Rate.  It seems you're suggesting it should stay high, so that the system isn't trying to write quite so often?  I was assuming keeping the flush rate low would prevent some sort of buffering/cacheing overflow (I kept crashing).
Ok, i'll come back with some firm data once I've tried tweaking your suggestions.   

gary2013

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Re: EOS M: GOP, BITRATE, FLUSH RATE settings for H264
« Reply #4 on: February 22, 2014, 02:13:18 AM »
I have never tried the flush rate that high until today. and i also saw before that the bitrate setting will depend on ISO. meaning, the higher the iso setting i use, the lower the bitrate had to be set so it would not crash. usually use between 100 to 1600 iso. but when i tried 320-0, i had to lower the bitrate. a CBR of 2.5 seemed to work the best for all iso settings. these tests results i just posted here were all iso 800. i do not know if these high numbers are good or worth using for some reason. it is just what i was able to set and working without crashing.