GH4 GH4 codec

S

steve phillipps

Veteran
As the EBU minimum codec for broadcast spec for HD is 50 mb long GOP or 100 mb I frame, presumably for 4k this codec needs to be 4x the data rate (at least)?
Looking at the GH4 it has this, at first glance, impressive 100mb/sec long GOP codec, but presumably that equates to a pretty poor, non-broadcast-spec 25 mb codec in HD.
Steve
 
Are you planning to broadcast 4K material ?

100Mbs 4k is good quality. It is hard to see any artefacts at 100% viewing.
 
steve phillipps said:
As the EBU minimum codec for broadcast spec for HD is 50 mb long GOP or 100 mb I frame, presumably for 4k this codec needs to be 4x the data rate (at least)?
Looking at the GH4 it has this, at first glance, impressive 100mb/sec long GOP codec, but presumably that equates to a pretty poor, non-broadcast-spec 25 mb codec in HD.
Steve
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You're making very unwarranted assumptions. The EBU's specification was for MPEG-2, and 4:2:2. The GH4 is MPEG-4, and 4:2:0. There is no way to translate the efficiency of h.264 (which is a vastly superior codec) in terms of bitrate. The EBU will eventually issue their recommendations, after conducting likely extensive testing, and the results may (or may not) surprise you, we'll just have to wait and see what they come up with.

In the meantime, I would think that someone should not be expecting a $1599 stills camera to be delivering footage suitable for broadcast. It may, but it would be a bit much to go expecting it.
 
Barry_Green said:
There is no way to translate the efficiency of h.264 in terms of bitrate.
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Actually you can. H.264 is about twice as efficient as MPEG2, so to achieve the same quality as MPEG2 at 50 Mb/s, H.264 only needs 25 Mb/s. This is a broad generalization, of course. There's more goes into image quality than bitrate, as your own past aritcles demonstrate. But I think it's still a good rule of thumb to know.
 
Vesku said:
Are you planning to broadcast 4K material ?

100Mbs 4k is good quality. It is hard to see any artefacts at 100% viewing.
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I don't broadcast anything, I just shoot it. Almost certainly a camera I would never shoot with myself, just thinking aloud, wondered how good the codec was at that data rate with all that data. Nanoflash and other external recorder bexcame very popular simply because a lot of internal codecs weren't up to broadcast and other demanding jobs, so it's obviously a big deal. When I saw specs for GH4 I thought wow, 100 mb/s, impressive, and then it occurred to me that it's a lot more data to compress.

Steve
 
Your reference to the NanoFlash is partly because in-camera codecs weren't generally recording 4:2:2, and 4:2:2 was part of the BBC requirements. They had established 50mbps @ 4:2:2 for long-GoP codecs, but that determination was made from MPEG-2. They held h.264 cameras to the same numbers, even though h.264 needs less bandwidth to deliver equivalent quality. I don't know if they ever revised the specs downward for h.264 efficiency.
 
Barry_Green said:
Your reference to the NanoFlash is partly because in-camera codecs weren't generally recording 4:2:2, and 4:2:2 was part of the BBC requirements.
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Well it doesn't really need that elaboration - the codecs weren't acceptable for broadcast in-camera, Nanoflash and others sorted that.
There will obviously be something similar for 4k when it actually becomes a reality, I get the impression / unwarranted assumption that it will in line with the HD one, so maybe 400 mb/s I frame or 200 long GOP, 422. Interesting question for me is whether a standard will be introduced that requires higher framerate, ie 4k / 60P for normal speed / sync - putting us in the same situation as with HD that many of the cameras out there won't be able to do slow motion in 4k, needing 120fps and higher to do that.

Steve
 
Vesku said:
100Mbs 4k is good quality. It is hard to see any artefacts at 100% viewing.
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People say that about all sorts of codecs, but just because it looks good doesn't mean it will once transmitted. That was the downfall of Super 16 - arguments raged for ages, Kodak vs the video manufacturers, about how it had loads more resolution that HD and was every bit as good if not better. The problem lay not in the original pictures but what happened to them once they went through the broadcast chain - the film grain caused the picture to fall apart once it had been squeezed and compressed through the transmission chain. Same thing happens to highly compressed codecs - no end of people in the early days of HDV lamented about how their footage was not acceptable for broadcast and yet when they played it back from their cameras on their big HD screen it looked as good as anything from the BBC or Hollywood.
Not saying the like of the GH4s 100 mb/s codec won't be up to it, I don't know, it just occurred to me that squeezing over 4 times as much data (?) down to 100 mb/s sounded quite a tall order.

Steve
 
Barry_Green said:
In the meantime, I would think that someone should not be expecting a $1599 stills camera to be delivering footage suitable for broadcast. It may, but it would be a bit much to go expecting it.
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Not sure on the point of this statement. DSLR's have been shooting broadcast for years. While there may be something inscribed on a scroll somewhere that states the EBU's standards, having worked for the European, US and Australian broadcasters constantly since the introduction of DSLR's in video, DSLR's are used EVERYWHERE even on Mid to High End production in both sports and entertainment.
 
vtwiz said:
Not sure on the point of this statement. DSLR's have been shooting broadcast for years. While there may be something inscribed on a scroll somewhere that states the EBU's standards, having worked for the European, US and Australian broadcasters constantly since the introduction of DSLR's in video, DSLR's are used EVERYWHERE even on Mid to High End production in both sports and entertainment.
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But almost always with an external recorder I'm sure. In that way that would indeed meet the EBU criteria - although in practice there are often other issues like moire, rolling shutter etc.

Steve
 
steve phillipps said:
But almost always with an external recorder I'm sure. In that way that would indeed meet the EBU criteria - although in practice there are often other issues like moire, rolling shutter etc.

Steve
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From my experience in TV post over the past 3 years almost every production uses 5D for B cam or GVs, frequently even for A cam interview set ups. I can count on one hand the amount of times we have received DSLR footage that has been used with an external recorder; usually the 5D is used because it's cheap and easy to use - they don't want to hire an external recorder too.

I believe the BBC specify you can use a certain amount of 'sub-HD' footage in a programme (not necessarily sub-HD resolution but footage that doesn't meet required bit rate standard), how this is enforced I have no idea as we have some shows that seem to be made up of 60-70% archive footage, 5D, GoPro, even still HDV on occasion.

We are seeing a bit of GH4 material trickle through (never got any GH1-3 footage) and have had a few cards from Blackmagic cameras but the 5D is still very much ubiquitous.
 
I could care less at this point what 4K standards might be, as NONE of the broadcast affiliates I deliver to accept 4K material.

I mainly produce broadcast TV commercials, which have different compliance standards from say a 30min TV show. Which is why I asked what type of work you were doing.

What type of content are YOU delivering?
 
I don't deliver anything, I'm just a cameraman and I use what I'm given, but it's all broadcast stuff, mostly for BBC, and it does need to fall within their tech guidelines - so I've never shot an EX3 or 5D or anything similar - started on Super 16, then Digibeta and last 5 years or more it's almost all been Varicam (tape and then P2) and HDCam, with a little XDCam HD, plus Phantom HD.

Steve
 
steve phillipps said:
Is it actually relevant to know what I'm doing?
Steve
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I was just trying to be helpful, narrow down the field, and try to point you in the right direction, since I have worked on commercials which aired on BBC, and the subject of acquisition codec was never even brought up.

But since you don't deliver anything, you just use what camera you are given, one might ask if your initial question is relevant? ;)
 
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