Pro,s and Cons iframe /long GOP

Dean Harrington · April 3rd, 2010, 05:34 PM

robin,
I record through the camera and also through the NanoFlash. I primarily use the NanoFlash as my primary footage. There was only one time when I needed backup and that was when I hadn't seeded my SDHC card properly in the EX3 ... the Nano save the day.

Robin Probyn · April 4th, 2010, 07:01 AM

Quote:

Originally Posted by Alister Chapman

When I shoot 3D I just use the Nano's as they start and stop in sync via the cable that CD made for me.

For me it's comes down to the fact that I can shoot at 100Mb/s long GoP and get quality that is as good as if not better than 220Mb/s I frame, but my media lasts twice as long, long term storage takes less space and copying files takes half as long. In the edit I hardly notice any performance difference. So there are genuine cost and time savings by using long GoP without any image quality implications.

So you get less time on your CF card recording iframe? or are you referring to 100Mbps as opposed to 220Mbps..

Thanks

Dan Keaton · April 4th, 2010, 07:53 AM

Dear Robin,

I-Frame Only is far less efficient than Long-GOP (up to a certain bit rate).

To be clear, at 100 Mbps, Long-GOP is far better in terms of quality than I-Frame Only.

Please remember that we are impartial here, we support both options in one device.

There is a very nice, quantifiable, increase in quality when going from lower bit-rate Long GOP (say 35 Mbps 4:2:0) to higher bit rates (say 100 Mbps 4:2:2). Of course some of the increase in quality is due to going to 4:2:2.

But as one goes from 100 Mbps to 140 Mbps to 180 Mbps the quality increase is less dramatic with each step. This is an example of diminishing returns.

Stating the obvious: As the Bit-Rate goes up the amount of time one can record on a CompactFlash card of a given size goes down.

Our 100 Mbps, 140 Mbps and 180 Mbps Long GOP 4:2:2 recordings are very high in quality.

Technically, a very slight increase in quality can be obtained by recording 280 Mbps I-Frame Only as opposed to 180 Mbps Long-GOP. This very slight increase in quality can be detected with the right instruments but would be hard to detect with one's eyes, or in Post.

With this background, if you are considering 100 Mbps, always choose Long-GOP, it will be much higher in quality.

If you have to deliver I-Frame Only (Intraframe), then choose a higher quality, higher bit-rate option. Choose at least 140 Mbps or 180 Mbps; 220 Mbps or 280 Mbps would be better, but of course your recording time per card will be reduced.

To be specific, Alister stated that 100 Mbps Long GOP is as good or better than 220 Mbps I-Frame Only. I agree.

And he gets approximately 2 times as much recording time with 100 Mbps Long-GOP.

Note: I edited an obviously incorrect statement above as pointed out by Adam.

Robin Probyn · April 4th, 2010, 08:24 AM

Thanks for the info.. I,ll question the prod co about why they want iframe at 100Mbps

Tim Kolb · April 4th, 2010, 11:58 AM

Quote:

Originally Posted by Dan Keaton

To be specific, Alister stated that 100 Mbps Long GOP is as good or better than 220 Mbps I-Frame Only. I agree.

Hi Dan,

The only caveat I'd add here is that when many (Final Cut) users think about 220 Mbps, they're thinking about ProRes. 220 Mbps ProRes is a different codec than 220 Mbps MPEG2. 220 Mbps ProRes has 10 bit color precision, whereas MPEG2 on the Nano is 8 bit at all bitrates...and ProRes is variable bitrate compared to the Nano's constant bitrate (at whatever setting)...

The basic idea here that Long GOP is better (more quality for the bitrate) than I-frame is one that I agree with...no question about it. As long as all other factors are equal.

I just think that our industry has many cases of over-generalization with the intent of trying to simplify concepts for users or customers, and while it probably adds confusion for some, I think attempts to present some of the shades of gray can be more enlightening for users in the long run.

Bitrate in general, I-frame vs Long GOP, 8 bit vs 10 bit vs ?, 4:4:4 vs 4:2:2 vs 4:2:0, DCT vs Wavelet, Constant bitrate (CBR) vs Variable bitrate (VBR), Log vs Linear, RGB vs Y'CbCr... They all combine to create different cocktails of image processing.

Then, there is also the question of 'runnability' in editing...

I'm not trying to start an argument so much as wishing to make sure that the idea of multiple factors contributing to a codec's image quality is out there.

(Disclaimer: I'm a Nano user...and a KiPro user. They each have their sweet spot. I also think that CineForm is an exceptional codec... I've also acquired to CineForm. If you would ask if I had a horse in this race, I guess I'd have to say "all of them.")

Dan Keaton · April 4th, 2010, 12:51 PM

Dear Tim,

I agree with all of your comments.

220 Mbps ProRes is an entirely different codec.

One nice thing about the nanoFlash, and in the spirit of this discussion, as long as we are discussing 4:2:2 nanoFlash footage (all of our 50 Mbps and above options are all 4:2:2), then all things are equal, except for the items that we are discussing, either the bit-rate or I-Frame versus Long-GOP.

And your point is valid.

So, when I said 220 Mbps some could have incorrectly inferred Apple ProRes 220 Mbps.

Also, when we discuss 100 MBps I-Frame Only (Interframe), some could incorrectly infer DVCPro HD (which is also 100 Mbps (in some modes), but an entirely different codec.)

You are in an elite group in using both a Ki Pro and a nanoFlash.

"Horses for Courses" comes to mind here.

Our strengths are offerring a very versatile product that produces very low-noise footage.

And many like our compact size and low power requirements.

Adam Stanislav · April 4th, 2010, 01:44 PM

Quote:

Originally Posted by Dan Keaton

Stating the obvious: As the Bit-Rate goes up, the size of the files goes down

You may want to rethink that statement, Dan. :)

Tim Kolb · April 4th, 2010, 02:33 PM

Quote:

Originally Posted by Dan Keaton

Dear Tim,

You are in an elite group in using both a Ki Pro and a nanoFlash.

"Horses for Courses" comes to mind here.

Our strengths are offerring a very versatile product that produces very low-noise footage.

And many like our compact size and low power requirements.

I like the Nano for exactly those reasons, and have been quite happy with the footage it produces.

Since I (as many of us) do this for a check, I use whatever the client requests, and the KiPro is a very popular device as well...

"Horses for Courses" (anybody know where the heck that saying came from?) is right.

Dan Keaton · April 4th, 2010, 02:41 PM

Dear Adam,

Yes, my mistake. I need to take a little longer in proofreading my posts.

Thank you for pointing it out.

I have corrected the original post.

Adam Stanislav · April 4th, 2010, 03:13 PM

You're quite welcome, Dan.

Mark Job · April 4th, 2010, 06:07 PM

Quote:

Originally Posted by Robin Probyn

I,ll be shooting with my HDX900.. not a big deal.. just wondered why some people like long GOP and some want i frame..

....Hi Robin: The reason I like I-Frame recording over Long GOP for very high end (Read Digital Cinema Origination and *Not* television), is two fold.

1. I can obtain very high image quality @ 280 Mbps in i-Frame recording with my XDR, which I consider to be slightly superior to Long GOP 180 Mbps.

2. Recording in I-Frame produces video files which are pretty much universally accepted by most major NLE post systems, such as Avid Media Composer and Final Cut Studio 7.x

* My standard approach to paying TV job shoots is to shoot in Long GOP MXF 50 Mbps setting. This produces Avid compatible Sony XDCAM HD 4:2:2 Full Raster video files equal to what the TV networks record on disc or tape. (Sony HDCAM SR is the only other exception).
** May I suggest as a basic rule of thumb, that if you're shooting for Network Television, and you don't know what their specs are, then always assume Long GOP 50 Mbps in MXF standard and you shall not go wrong ! Assume Avid Media Composer in their post and not Final Cut Pro (Including Discovery Channel).

Robin Probyn · April 4th, 2010, 08:29 PM

Hi Mark

Thanks for the advise.. I,ll remember it.

In this case they sent the settings(for EX3 use) I,ll be shooting HDX900.. they want QT so I guess FCP.. like you say, before I have shot Long GOP 50Mbps.. but it seems they want 100 Mbps QT iframe.. anyway have emailed to confirm iframe.. just now seems strange as everyone here says that at 100Mbps long GOP is a far better image..and fitting any NLE system doesnt seem to be a problem as they state QT.. ,

Thanks again all

Mark Job · April 5th, 2010, 07:02 AM

Quote:

Originally Posted by Robin Probyn

Hi Mark

Thanks for the advise.. I,ll remember it... just now seems strange as everyone here says that at 100Mbps long GOP is a far better image..and fitting any NLE system doesnt seem to be a problem as they state QT.. ,

Thanks again all

.....If they say I-Frame 100 Mbps, then they're probably posting on Avid Media Composer. Please be advised anything in Long GOP MXF which is over 50 Mbps *Will NOT work in Avid !*

Dusty Powers · April 5th, 2010, 07:08 AM

Robin:

The HDX-900 has a Video Bit Rate of 100mbs with 4:2:2 Sampling and Intra-Frame Compression. I wouldn't see a reason to duplicate this on a CF card unless a tape deck is not available for transfer or you just want to record at the same time on the NanoFlash in order to save footage for your reel. Once you pass off that tape to a client it's usually gone. If it's for my reel then I would record at 100mbs/Long GOP as many have suggested on this forum. You can't go wrong with this setup.

With that said, if my client wanted footage on a CF card while one is shooting with the HDX-900 then I would still roll tape at all times especially if one is not familiar with the process of transfer and backup of digital media. Why would one not want to roll tape at the same time if it's available? It's one sure way to be responsible in this business and save a major problem from developing.

I don't question what my clients want as far as their record formats. They get locked into a particular standard and don't want to venture in other directions. I'll let them deal with that. I feel my responsiblity is to get the best images possible for the editor. I try to keep in the back of my mind, "it's not the format, but it's what you do with the format" attitude. I will offer suggestions and better ways of doing things from time to time if I think it will help the process. Introducing the Nano to a client can be a tough sale especially if one is still using tape. I'd rather not have a client turned off by a bad experience with the Nanoflash from the beginning.

Robin Probyn · April 5th, 2010, 06:48 PM

Yeah I,ll record to tape for sure.. so do you charge for the tapes? if they dont want tapes in the first place? They wanted P2.. but I asked if I could use HDX900 with nano.. luckily seems they are ok with the nano as they have their own set details for it.. (for use with a EX3)
Yes they dont have a deck for the Pana tapes,so didnt want to just shoot on the HDX900.Fair enough..

What is your procedure for backing up CF cards..? besides the tape backup..

Thanks for the advise..

April 3rd, 2010, 05:34 PM	#16
Dean Harrington Major Player Join Date: Nov 2002 Location: Tokyo Posts: 898	record backup ... robin, I record through the camera and also through the NanoFlash. I primarily use the NanoFlash as my primary footage. There was only one time when I needed backup and that was when I hadn't seeded my SDHC card properly in the EX3 ... the Nano save the day.

April 4th, 2010, 07:53 AM	#18
Dan Keaton Inner Circle Join Date: Dec 2002 Location: Augusta Georgia Posts: 5,421	Dear Robin, I-Frame Only is far less efficient than Long-GOP (up to a certain bit rate). To be clear, at 100 Mbps, Long-GOP is far better in terms of quality than I-Frame Only. Please remember that we are impartial here, we support both options in one device. There is a very nice, quantifiable, increase in quality when going from lower bit-rate Long GOP (say 35 Mbps 4:2:0) to higher bit rates (say 100 Mbps 4:2:2). Of course some of the increase in quality is due to going to 4:2:2. But as one goes from 100 Mbps to 140 Mbps to 180 Mbps the quality increase is less dramatic with each step. This is an example of diminishing returns. Stating the obvious: As the Bit-Rate goes up the amount of time one can record on a CompactFlash card of a given size goes down. Our 100 Mbps, 140 Mbps and 180 Mbps Long GOP 4:2:2 recordings are very high in quality. Technically, a very slight increase in quality can be obtained by recording 280 Mbps I-Frame Only as opposed to 180 Mbps Long-GOP. This very slight increase in quality can be detected with the right instruments but would be hard to detect with one's eyes, or in Post. With this background, if you are considering 100 Mbps, always choose Long-GOP, it will be much higher in quality. If you have to deliver I-Frame Only (Intraframe), then choose a higher quality, higher bit-rate option. Choose at least 140 Mbps or 180 Mbps; 220 Mbps or 280 Mbps would be better, but of course your recording time per card will be reduced. To be specific, Alister stated that 100 Mbps Long GOP is as good or better than 220 Mbps I-Frame Only. I agree. And he gets approximately 2 times as much recording time with 100 Mbps Long-GOP. Note: I edited an obviously incorrect statement above as pointed out by Adam. __________________ Dan Keaton Augusta Georgia Last edited by Dan Keaton; April 4th, 2010 at 02:38 PM.

April 4th, 2010, 12:51 PM	#21
Dan Keaton Inner Circle Join Date: Dec 2002 Location: Augusta Georgia Posts: 5,421	Dear Tim, I agree with all of your comments. 220 Mbps ProRes is an entirely different codec. One nice thing about the nanoFlash, and in the spirit of this discussion, as long as we are discussing 4:2:2 nanoFlash footage (all of our 50 Mbps and above options are all 4:2:2), then all things are equal, except for the items that we are discussing, either the bit-rate or I-Frame versus Long-GOP. And your point is valid. So, when I said 220 Mbps some could have incorrectly inferred Apple ProRes 220 Mbps. Also, when we discuss 100 MBps I-Frame Only (Interframe), some could incorrectly infer DVCPro HD (which is also 100 Mbps (in some modes), but an entirely different codec.) You are in an elite group in using both a Ki Pro and a nanoFlash. "Horses for Courses" comes to mind here. Our strengths are offerring a very versatile product that produces very low-noise footage. And many like our compact size and low power requirements. __________________ Dan Keaton Augusta Georgia

April 4th, 2010, 02:41 PM	#24
Dan Keaton Inner Circle Join Date: Dec 2002 Location: Augusta Georgia Posts: 5,421	Dear Adam, Yes, my mistake. I need to take a little longer in proofreading my posts. Thank you for pointing it out. I have corrected the original post. __________________ Dan Keaton Augusta Georgia

April 4th, 2010, 08:24 AM	#19
Robin Probyn Major Player Join Date: Jan 2010 Location: Tokyo Posts: 590	Thanks for the info.. I,ll question the prod co about why they want iframe at 100Mbps

April 4th, 2010, 03:13 PM	#25
Adam Stanislav Trustee Join Date: Oct 2009 Location: Rhinelander, WI Posts: 1,258	You're quite welcome, Dan.

April 4th, 2010, 08:29 PM	#27
Robin Probyn Major Player Join Date: Jan 2010 Location: Tokyo Posts: 590	Hi Mark Thanks for the advise.. I,ll remember it. In this case they sent the settings(for EX3 use) I,ll be shooting HDX900.. they want QT so I guess FCP.. like you say, before I have shot Long GOP 50Mbps.. but it seems they want 100 Mbps QT iframe.. anyway have emailed to confirm iframe.. just now seems strange as everyone here says that at 100Mbps long GOP is a far better image..and fitting any NLE system doesnt seem to be a problem as they state QT.. , Thanks again all

April 5th, 2010, 07:08 AM	#29
Dusty Powers Regular Crew Join Date: Nov 2009 Location: Wilmington, NC Posts: 31	Robin: The HDX-900 has a Video Bit Rate of 100mbs with 4:2:2 Sampling and Intra-Frame Compression. I wouldn't see a reason to duplicate this on a CF card unless a tape deck is not available for transfer or you just want to record at the same time on the NanoFlash in order to save footage for your reel. Once you pass off that tape to a client it's usually gone. If it's for my reel then I would record at 100mbs/Long GOP as many have suggested on this forum. You can't go wrong with this setup. With that said, if my client wanted footage on a CF card while one is shooting with the HDX-900 then I would still roll tape at all times especially if one is not familiar with the process of transfer and backup of digital media. Why would one not want to roll tape at the same time if it's available? It's one sure way to be responsible in this business and save a major problem from developing. I don't question what my clients want as far as their record formats. They get locked into a particular standard and don't want to venture in other directions. I'll let them deal with that. I feel my responsiblity is to get the best images possible for the editor. I try to keep in the back of my mind, "it's not the format, but it's what you do with the format" attitude. I will offer suggestions and better ways of doing things from time to time if I think it will help the process. Introducing the Nano to a client can be a tough sale especially if one is still using tape. I'd rather not have a client turned off by a bad experience with the Nanoflash from the beginning.

April 5th, 2010, 06:48 PM	#30
Robin Probyn Major Player Join Date: Jan 2010 Location: Tokyo Posts: 590	Yeah I,ll record to tape for sure.. so do you charge for the tapes? if they dont want tapes in the first place? They wanted P2.. but I asked if I could use HDX900 with nano.. luckily seems they are ok with the nano as they have their own set details for it.. (for use with a EX3) Yes they dont have a deck for the Pana tapes,so didnt want to just shoot on the HDX900.Fair enough.. What is your procedure for backing up CF cards..? besides the tape backup.. Thanks for the advise..