Bit rate investigation

[Critical Point]

Yes, yes, please tell us the best settings for H.264 (without audio). I don't understand those settings also, and I can't find any explications.

[1%]

I can imagine the processors only being designed for those as the optimal.

The encoder has fixed modes only... other image processors are fine.

Instructions are all in this thread... but old stuff not ported yet. So you can do flush + gop and make it record max "normal" qp all the time. No flipping or direct quality control yet.

[jankyy]

what's a good (and safe!) setting / combination for shooting .h264 with approx. 80-160Mbit/sec? in my ML encoder menu, the options are:

- Bit Rate (0... 15 or more)
- InitQP (off ... 50)
- Flush Rate (auto ... 4frames... 50frames)
- GOP size (default ... 100frames)
- Autoload conf (off / on / override)
- Config select (off/h264.ini  /  CBR fixed QP   /   VBR   / Rate Control)

i can't find an explanation for these particular options anywhere???... thanks so much -

jan

p.s. i have ML from June 2013, a 6D and SanDisk Extreme Pro 32GB

p.p.s and how do these settings relate to the canon in-camera settings ALL-I and IPB? which overrides which? (if there's an explanation already somewhere, please hit me upon it! thx...)

[kgv5]

I was discussing this with 1% before, try this:

1080p IPB

- Bit Rate OFF
- InitQP OFF
- Flush Rate (auto ... for sound of 4 if you don't need a sound)
- GOP size 24
- Autoload conf: override
- Config select: Rate Control

It should give very stable IPB with 60-70 mbps bitrate which theoretically should look better than 60-70 ALL-I.

[Critical Point]

But for the maximum quality (without sound), what settings ?

[jankyy]

I was discussing this with 1% before, try this:

1080p IPB

- Bit Rate OFF
- InitQP OFF
- Flush Rate (auto ... for sound of 4 if you don't need a sound)
- GOP size 24
- Autoload conf: override
- Config select: Rate Control

It should give very stable IPB with 60-70 mbps bitrate which theoretically should look better than 60-70 ALL-I.

thanks very much, kgv5!!!

looks like it's working well for 1920/25fps IPB, gives me ca. 61Mbit/sec, which is a good number for me to handle...
just wondering:

- is the GOP size 24 the same choice for 24fps or 25fps?
- what would be the respective settings for 1280p50 IPB? (for now, a test with the above setting gives me about 106Mbit/sec, which would still be fine for my SanDisk ExPro card i guess)

thanks - jan

[1%]

Max gop is FPS so for 25 P its 25.. 50p its 50, etc.

[jankyy]

Max gop is FPS so for 25 P its 25.. 50p its 50, etc.

strange:
- it's only working with GOP size exactly 24  (both at 1920p25 and 1280p50 IPB)
- not working with GOP 25 or 4 or... it just doesn't record, and does a restart after 10secs...

anymore insight in these settings?

[1%]

What about 50?... maybe uneven gop size doesn't work. This is all from canon, all I can do is set it.

[jankyy]

i just tested diefferent GOP sizes:

- 2 and 4 and 25 and 50 - they all don't work at all - in the upper right corner, A and B and the % stay at zero, after 10secs the camera restarts...
- only GOP size 24 frames seems to work.

i don't understand why; and i also don't understand the big difference in bit rate when using the 1920p25 or the 1280p50 resolution:

- 1920p25 gives approx. 60Mbit/sec
- 1280p50 gives apporox 105Mbit/sec (which is a lot of data, and takes lots more time to convert to DNxHD...)

any idea? thanks! jan

[1%]

I'll check on gops.. I have to rewrite this for 50D... 50/60FPS vs 24 or 30 is why the data rate is so high.

[jankyy]

I'll check on gops.. I have to rewrite this for 50D... 50/60FPS vs 24 or 30 is why the data rate is so high.

trial and error:
- i found that as settings for GOP size: 24, 12, 6 and 3 are working, for 1920p25 IPB (other GOP sizes do not record at all)
- but the GOP size doesn't seem to affect the file size / bitrate (/quality?) at all

and still wondering: data rate for 1920*1080, 25fps and 1280*720, 50fps should be about the same; yet, using the RateControl mode produces very different data rates for these modes...

sorry to bother, i know you're very busy working on the raw option, but for the time being it would be just great to have some .h264 settings that work safely (with options that i can get my head around  ). thanks again - jan

[jgharding]

I know most of the dev time seems to now be on raw modes, but did the 600D I frame mode ever reach a stable build that one can use to shoot with?

I'm keen to try it, but is it available in friendly form for shooting?

[1%]

but the GOP size doesn't seem to affect the file size / bitrate (/quality?) at all

It affects I to P ratio. Analyze the files...

[jgharding]

Ah yes I found Tragic Lantern.

I'm mainly interested in getting an I-frame (GOP1) with sound, so I'll fiddle about

As far as I can see GOP1 with CBR 2.3 or so should be good results? Do I need to change slice in order to get sound too though?

On the 550D I could do about 2.8 with no sound, but I'd like I-frame and sound if possible...

I shall experiment.

raw would be wonderful but current limitation make it impracticable i think.

If the data to the buffer could be cute (maybe 10-bit raw?) it'd become more practical, but for now it's H264 and the mosaic engineering anti-aliasing filter...

That filter makes the bitrate increases a lot more meaningful as far as I've been able to determine... the data isn't soaked up by false detail from aliasing.

[jgharding]

I found that GOP1 and all the way down on the Q-scale gives good high bitrate.

Noise can be removed easily and motion is nice. I didn't touch any of the other settings.

I'm curious as to how a consistently higher rate can be squeezed out though, but obviously beyond a point the detail isn't there, so for now this seems reliable, good and has sound.

Any other tips out there for solid I-frame?

[jgharding]

I did try the raw mode, and it is wonderful for dynamic range and colour, but obviously at such reduced resolution and sensor crop it's quite a compromise. Damn that little buffer.

I'll definitely keep a close eye on it and keep testing it though, and have a trawl back through this thread to find some more H264 settings...

[1%]

Heh, the old builds I think had sraw + slice.. in theory the most free memory should be in sraw.. so does recording time go up @ slice 87?

New builds still need this, will have to see.. also have to put combine dialog timer hack + slice + sraw memory.. I'm assuming this combination might be good.

[Critical Point]

Isn't there a way to make the H.264 codec not rescale the image so many times ? I bet that is one of the major causes of poor image quality compared to a GH2.

[jgharding]

Heh, the old builds I think had sraw + slice.. in theory the most free memory should be in sraw.. so does recording time go up @ slice 87?

New builds still need this, will have to see.. also have to put combine dialog timer hack + slice + sraw memory.. I'm assuming this combination might be good.

I've missed a bit of development recently so I'll need to look up what sRaw is... I'll trawl some threads...

[wenen]

1% is it easy to go back to the old build from the new one?

[jgharding]

1% is it easy to go back to the old build from the new one?

Keep each Autoexec.bat file that you try out stored in different logically named folders on your PC. Then you can swap and test builds as and when you like.

[1%]

The encoder takes fixed sizes, so I don't think we can eliminate any scaling... at least there is crop mode.

[jgharding]

Heh, the old builds I think had sraw + slice.. in theory the most free memory should be in sraw.. so does recording time go up @ slice 87?

New builds still need this, will have to see.. also have to put combine dialog timer hack + slice + sraw memory.. I'm assuming this combination might be good.

I can limit the encoder to around 160mbps cap using slice control. With GOP1 I never fill the buffer. My sound is off, but I'll try it with it on.

Slice control really is brilliant. With:

Min BR: 130
Max BR: 160
Drop 1: 140
Drop 3: 145
Taper Rates: Enabled

PicPC: 0

I never get in trouble. Well, if I have a super complex scene like a carpet all in focus at f22 and ISO6400, and start recording at slice 87 it'll overrun and drop down to highslice, then settle. If I start such a scene at slice 120, it'll settle very quickly, capping around 160mbps and only buffer dropping to a higher slice in an absolute emergency.

These settings let me maintain maximum possible from the stock H264 method. It's a great bit of coding.

I have a SanDisk 95MBs UHS1 card and the TXi filter installed.

[jankyy]

Slice control really is brilliant. With:

Min BR: 130
Max BR: 160
Drop 1: 140
Drop 3: 145
Taper Rates: Enabled

PicPC: 0

I never get in trouble.

please help me understand:
is this something that works for Canon 6D, too? where would I find these settings?

thanks - jan