Cineform HQ codec settings - color space

[Interface]

Sorry for the title, I meant Canopus not Cineform...

In AVCHD2HQ converter there are 2 Canopus HQ codec options to chose from:


1. (default one) RGB has ITU-R BT.601 range
2. convert RGB range [0,255] as IRE [0,100]

if I get it right 2nd is in 16-235 range as opposed to 0-255 range of the first option.

Here is my question: Since the original avchd .mts file looks exactly the same as 16-235, is there any point in transcoding it using 1st option?
Is there any information in the picture that is gained when "adding" those 0-15 range and 236-255 in highlights?
I think that it just brightens the image up thus giving me the impression that there is something hidden in those blacks and vice versa for highs, but I'm not sure about anything anymore.

An example:

 

[PDR]

It depends on several things

If your camera shoots excursions >235 and <16 (HMC150 is capable) , many people like to keep all that information and have access to it when doing their color corrections, etc..

I don't use that canopus software, but if canopus is applying a clamp instead of a passthrough when you choose that, then you would lose some of that that information (brighter than bright, darker than dark).

Remember small excursions are legal (you see this all the time on Hollywood studio produced DVD's and blu-ray)

Also it depends on what software editor you are using; some will clamp values to strict legal 16-235 (or 0-100 IRE) , depending on the input format (i.e. some treat different input files differently, e.g. premiere does this for input files it doesn't have presets for so I suspect it would treat canpus HQ files the same way - check the waveform monitor and do some tests on your software)

 

[Interface]

I have hmc152 and I use premiere cs4.

So, did I get it right:

Hmc actually captures image that has color range from 0-255 using avchd codec and than later on player or editor or converter etc. clamp it to IRE0-100 wich is 16-235 in rgb terms?
And mentioned canopus hq codec allows me to transcode original avchd into 0-255 range .avi file that, when imported to premiere does not get "squashed" to 16-235, because there is no preset for that particular codec, though if there was one it would probably "legalize" that video file to ire0-100 (in preview and export)?

I don't need to go into too much tech details with this, I'm just trying to understand the basics and chose trancoding pipeline which will suit me the best, since native avchd editing has become too unpredictable, to say the least.

thanks

 

[PDR]

I have hmc152 and I use premiere cs4.

So, did I get it right:

Hmc actually captures image that has color range from 0-255 using avchd codec and than later on player or editor or converter etc. clamp it to IRE0-100 wich is 16-235 in rgb terms?
And mentioned canopus hq codec allows me to transcode original avchd into 0-255 range .avi file that, when imported to premiere does not get "squashed" to 16-235, because there is no preset for that particular codec, though if there was one it would probably "legalize" that video file to ire0-100 (in preview and export)?

I don't need to go into too much tech details with this, I'm just trying to understand the basics and chose trancoding pipeline which will suit me the best, since native avchd editing has become too unpredictable, to say the least.

thanks

Yes, that's basically what happens in PP. It doesn't matter if canopus (or any other format) uses a certain range, if PP decides it wants to do it differently.

Even if canopus expands the range to full 0-255, PP will likely "squash" to 16-235 (or 0-100 IRE)

Look at the YC waveform in PP.

The HMC150 can shoot excursions beyond "legal" range and there is usuable data there.

I want you to test your workflow: If you import a native HMC150 file that has highlights into PP - look at the waveform , then compare to the canopus version, you will likely see clamping .

I can't confirm if this happens with canopus HQ (I don't use it) , but I would almost 99% certain it will since this behaviour occurs with just about everything else that it doesn't have a preset for (except v210) - I've done dozens of tests on other intermediate formats.

 

[Interface]

 

[PDR]

Unfortunately, that pretty much confirms my suspicions and is the same behaviour as most other intermediate formats. What settings was CanopusHQ using out of curiosity (not that it matters....) ?

Note, other software may decode the CanopusHQ files with the intended range & settings - i.e. this is a PP "quirck" or behaviour.

Note, native AVCHD decoding in Adobe CS4 has it's own issues, so you shouldn't edit native AVCHD (interlaced chroma bug decoding even with 24pN footage - there were several threads on this if you do a quick search)

Hopefully CS5 will address many of the bugs, or at least give you the option of adjusting decode settings , or more control over colorspace

 

[Interface]

Well, I have avchd2hq converter and it has only basic Canopus HQ options, and it was set to the highest quality and first option for color space (.601 range). Original avchd is 1080p25.

When compared in vectorscope, avchd converted to cineform neoscene and canopus hq (with codec set to 0-100IRE) is allmost exactly the same.

Considering the notorious bug I must have not wanted to hear about it since I finally configured my hardware and software to work with avchd and cs4 package.
But it is as it is and so, I have no option but to transcode before adobe, seems like I'd go with canopus HQ 'cause it is free and it looks very similar if not the same as neoscene. Or there is something more that I should be aware of with this choice?

One more thing, If something (not h264) is encoded from AME as h264 will it get diseased?

 

[PDR]

When compared in vectorscope, avchd converted to cineform neoscene and canopus hq (with codec set to 0-100IRE) is allmost exactly the same.

It looks almost the same because when you set it to 0-100, then canopus is doing the levels conversion to 0-100 instead (ie the clamping), and that matches what Adobe is doing.

But it is as it is and so, I have no option but to transcode before adobe, seems like I'd go with canopus HQ 'cause it is free and it looks very similar if not the same as neoscene. Or there is something more that I should be aware of with this choice?

For editing speed, another option is offline editing (proxy editing), but when you swap back to "master" for final render, it has to be a format that is decoded properly (ie. not native AVCHD)

For quality, the "best" that works for Adobe products is v210 (uncompressed 10-bit 4:2:2) , but only if you don't use Adobe to encode to v210 in the first place (the artifacts will be passed along otherwise). It's about 20-30x the size of your native HMC files

One more thing, If something (not h264) is encoded from AME as h264 will it get diseased?

If it's decoded that way internally by PP or AME, it will pass whatever artifacts along to the encode. Streams have to be decoded in order to be encoded. The point of colorspace conversion (from Y'CbCr to RGB and back to Y'CbCr) and the equations used to define those conversion causes a lot of headache as you can see (i.e. where black is defined, and where white is defined, along with the R,G,B coefficents)

Now define "diseased". Do you mean the interlaced chroma bug, or dynamic range compression (levels clamping)?

 

[Interface]

Thanks for your help PDR,

My goal is to edit online, so I'll have to find some way to transcode. What non adobe app can I use to encode avchd to v210? I need something small and standalone.

Let me rephrase my last question because I did not quite understand the answer:

If I for example encode whatever footage (some other than h264 that gets affected by the decoder bug) from premiere as h.264 - will it be bug free? Or should I forget h264 as a bug free exporting option too?

 

[PDR]

My goal is to edit online, so I'll have to find some way to transcode. What non adobe app can I use to encode avchd to v210? I need something small and standalone.

v210 isn't very edit friendly . High data rates ~1Gbps , so you need HDD in Raid0 or some SSD's. Online edit is difficult with it (i.e. not very smooth). It's meant as the lossless "master" for color correction, vfx and final render

I use ffmpeg and avisynth to do this, but you may find it difficult to use since they are code based and command line. There are some GUI's for ffmpeg (e.g. avanti), but you have to configure it to encode v210.

You can use AME to encode to v210, but you have to bypass it's internal decoding to avoid the interlaced chroma bug. You can do this through decoding with avisynth scripts and a decoder that works without errors, e.g. ffdshow with ffmpeg-mt or divx h.264 decoder work fine (PP has an avisynth import plugin and it works with AE too) - again , if you're not familar with avisynth the learning curve is a bit steep

Provided Canopus is doing the conversion correctly, you are not losing that much by using it, just a bit of dynamic range. For example, it might be worth it to do it that way for some people to get things done faster.

Let me rephrase my last question because I did not quite understand the answer:

If I for example encode whatever footage (some other than h264 that gets affected by the decoder bug) from premiere as h.264 - will it be bug free? Or should I forget h264 as a bug free exporting option too?

If it's decoded properly, the export will be fine. If there is a problem anywhere along the chain, it gets passed along to the encode.

e.g. if you encode to v210 properly, (or canopus HQ, assuming it's done correctly) , import & edit in PP, you can export from AME with h.264 or any other format fine without artifacts.

 

[GrahamH]

The headlights in this framegrab show the extent to which AVCHD footage from the HMC150 and 40 will allow highlights go "out of range" (scroll right to see the scope view). This is for a raw mts file ... if I transform to Cineform intermediate it looks exactly the same, not sure about Canopus as I don't use it. Some Premiere filters allow you to 'drag down' these highlights to regain extra detail within 100IRE - "fast color correction" is one. But other filters clamp at 100IRE as soon as you apply them - for example "RGB color corrector".