《电影与数字时代》杂志关于 ALEXA SUP 9.0 的访谈(中)

我们来聊聊9.0升级后的元数据特性吧,比如LDS镜头信息系统和/i技术

马克:现在所有ALEXA摄影机都能原生支持/i技术了。如果在ALEXA机身上使用Cooke /i镜头或是Angenieux /i镜头,机器会自动从电子触点读取镜头信息并写入元数据中。对于ALEXA我们的开发理念是在所有文件格式中保存尽可能多的元数据。ARRIRAW有元数据,QuickTime ProRes和MXF DNxHD有元数据,HD-SDI的录制信号输出和监看输出也都包含了元数据。有个软件叫Lightcraft,它可以实时读取并处理ALEXA HD-SDI信号中的元数据。我记得Transvideo的监视器在接入HD-SDI时会在屏幕上显示元数据和图形化的景深读数。元数据一直都处于一种很微妙的境地。这几十年大家都在谈元数据。我们要是大力推广它,总有人会找到它的用武之地。而现在已经可以看到这个趋势了。

 

怎样配合使用Codex Data Logger One外置元数据记录器?

 

亨宁:Codex Data Logger One是给那些不准备单独通过摄影机交付元数据的客户准备的。它和Codex Vault一起组成一套后期工作站,汇总来自其他镜头的图像和数据。用Vault可以进行各种文件操作,为剪辑、备份和离线编辑准备各种格式的文件,同时还能直接导出到数据库。所以说Codex更像是一种高度集成的系统,它能处理海量数据并兼容不同种类的摄影机。

[Codex Data Logger One还可以记录像惯性数据和GPS之类的额外信息。它可以支持/i Squared,与包括Preston在内的其他设备整合,在不同摄影机和镜头之间能保持高度一致性。]

 

马克:对于ALEXA来讲可能不是必须的配件,因为ALEXA在机内直接记录元数据。对于其他没有这个功能的摄影机,Data Logger记录器可以帮忙记录镜头信息。我们想把尽可能多的功能都整合到ALEXA机内,比如LDS镜头信息系统等所有摄影机数据都完整记录。对于Plus系列的机器,连遥控功能都已经整合到了机内,完全不需要连接任何接收器。一些其他厂商的摄影机则需要安装各种外部设备来记录镜头信息或者使用无线跟焦。而ALEXA XT Plus把所有东西都做到了机内,不必加装过多附件,连接线缆也更少,能最大限度地把设备故障率降到最低。

 

如果使用LTO磁带进行存档的话,元数据也会一并包括进去吗?

 

亨宁:是的,对于ARRIRAW格式,元数据永久嵌入在ARRIRAW的文件标头内。上周我们发布了ARRIRAW DPX多组块文件标头描述规范[由Codex研发]。在这之前,DPX文件很是让人头疼,虽然它是业内的标准格式,但对于元数据的嵌入却没有任何规范。我们编写了一个组块式文件标头,把整个ARRIRAW的文件标头复制到DPX文件内并将相关描述嵌入其中。这样的话像The Foundry (Nuke) 等后期制作软件就能在ARRIRAW已被转换为DPX格式的情况下获取完整的元数据。即使元数据被改动也可以调出原始版本进行检查。一切都是开放透明的。

 

举个例子,有人在用ARRIRAW文件转换器执行操作的时候可以发现有一个文件由于某种原因并没有使用800ASA处理,而是用了200ASA。或是白平衡被改动过。这项功能在特效领域绝对前所未有。

我跟《少年派的奇幻漂流》的特效总监聊过,他告诉我说当时摄影师克劳迪奥·米兰达(Claudio Miranda,ASC)想找一个使用25毫米Master Prime定焦镜头拍摄的画面。他在数据库中检索所有25毫米镜头拍摄的画面后很快就找到了。这可以让特效从业人员省不少事,毕竟他们那么辛苦,赚的钱也不多。LDS 镜头信息系统和智能化的元数据处理能给他们帮很多忙。就处理这些数据本身来讲没什么趣味性,也没有值得炫耀的成分,但使用得当的话可以省下不少时间、金钱和人力物力。

 

你们俩都知道我一直倡导使用元数据,但是好像没什么人真正懂得利用它。

 

马克:这是个过程。最近有个很好的案例。《权力游戏》在爱尔兰拍摄的时候我去探过班。因为HBO是个挺大的电视台,做事很有意思,而且没有上面制片公司的约束,所以他们有一套自己的流程。大量使用了元数据。拍摄选用ALEXA和Codex录机,存储卡拍完从Codex取出之后,就放入后期工作站内的一台禁用录制功能的Codex Onboard M内。他们会检查所有素材保证元数据没有问题。如果最开始就有错误的元数据,那么这个错误会蔓延到所有的交付和代理文件,这时候再要修补就已经太晚了。所以说他们进行其他工作之前,甚至连备份之前都会仔细检查元数据。我以前从来没有看见过像这样第一步工序就是检查元数据的。

 

[由于拍摄使用了Codex,片方可以利用Codex全线产品包含的虚拟文件系统(VFS),VFS的优势之一就在于可以调阅并编辑元数据。]

 

元数据检查完毕之后就做备份,然后输出每日素材和进行其他必要处理。这个案例可以充分说明元数据对于他们整个工作流程的重要性。

 

很多片子使用Avid剪辑,将原始ARRIRAW套底为DPX文件进行调色。你在ARRI影视部门也用DPX文件吗?

 

亨宁:我们也用DPX文件。有时候需要做大量特效的客户会选择Open EXR。DPX文件调色效果真的是非常好,因为所有ARRIRAW的处理都在套底和调色之前完成,调色过程中就不需要实时去拜尔了。直接用ARRIRAW调色当然也可以,我们觉得和DPX质量完全一样,两者都是Log C广色域格式,调色时最好先套用一个LUT。

 

但调色时元数据是不是就丢失了?

 

亨宁:这次加入向DPX嵌入元数据的功能之后就不会丢失了。关键在于一定要把ARRIRAW的白平衡和曝光值调整妥当之后再输出最终的DPX文件进行调色配光。

 

整个调色过程都能调阅元数据是不是更好?比如摄影师在机房参与调色的时候,第105个场景的第6条有个标注不见了,说的是画面应该偏暖,天空亮度要再压下来一点。场记表也找不到。

 

马克:你说的很对。不过现在的新趋势是在拍摄现场调色。今年我去美国参观了好几个片场,其中包括《X战警:未来昔日》和新版《哥斯拉》。这些片场的DIT技师就像调色师一样。摄影师不断调整各种参数,让预览的画面看起来就像调过色一样。CDL色彩决定表和录制文件会一起发到相关部门生成每日素材,他们把CDL套用在这些素材上以匹配片场的预览画面。有时候CDL也会被用于正式调色的参考。这种情况我遇到过两种流程,一种是片场只做一级校色,导出CDL并制作每日素材,正式调色时进行完善。第二种情况是摄影师在当日拍摄完毕后去一节特殊的拖车内做一级、二级和局部校色,甚至还会直接输出DPX代理文件给特效部门做参考,这样一来做特效的时候对最终效果会更有把握。

 

这样确实挺好,尤其是后期调色时摄影师没收到邀请或档期出现冲突的时候。

 

马克:结果就是现在大家都直接在片场做调色。因为很多片子都这么做,DIT技师都快变成现场调色师了。我们考虑到了这一点,于是XT系列摄影机可以直接从DIT技师的电脑使用网线导入CDL文件,并将其嵌入到相应的ARRIRAW文件内。

 

怎么嵌入的呢?作为元数据吗?

 

亨宁:元数据的文件标头有些剩余空间。我们把ARRI文件标头的技术规格分发给了包括Codex在内的所有合作伙伴,Codex把相应的数据写入ARRIRAW文件内并在整个流程中保留。

 

只有Vault可以支持吗?还是所有录机都可以支持?

 

亨宁:只要使用Codex虚拟文件系统就可以了,跟Vault之类的硬件没有关系。核心就是Codex虚拟文件系统[所有的Codex产品都包括这个特性]。

 

马克:Vault可以支持,有Codex虚拟文件系统的授权的话Capture Drive单槽和双槽型号也可以支持。支持CDL文件嵌入特性的就包括这三个硬件平台。

 

大部分DIT技师都是用什么软件在拍摄现场调色的?

 

亨宁:在我看来大部分都用的是Resolve。这套系统很不错,有免费的Lite版可以下载而且功能强大。我刚才还看了一下,完整版的功能免费版几乎都有,就是不支持降噪、立体3D和调色台,分辨率的最高限制是UHD 2160p。大制作一般用的是Colorfront OSD,应用范围比较广,不过Colorfront的强项其实是输出成片和每日素材。

 

马克:《X战警:未来昔日》用的是EFilm Colorstream软件。其他片子用过Pomfort LiveGrade。所有DIT技师用的硬件清一色都是Blackmagic DesignHD-Link,真的是人人都在用。软件各有各的选择,但Blackmagic DesignHD-Link人手一台。

 

亨宁:HD Link是个信号处理设备,可以加载现场创建的3D LUT并在片场监视器和视频回放区显示。

 

 

FDT interview about ALEXA SUP 9.0 (II)

Let’s talk about metadata in 9.0—LDS and /i support.


Marc: We now have built-in /i system support for all the ALEXA cameras. If you put a Cooke/i lens or an Angenieux /i lens on the ALEXA it will be able to read that data through the lens connector and store the metadata. Our philosophy with the ALEXA is we’re happy to take all the metadata we can get, and put it everywhere we can. So the ARRIRAW has the metadata. QuickTime ProRes and MXF DNxHD contain metadata. The HD-SDI stream contains metadata on the Rec-Out, as well as the Monitor Out. There’s an application called Lightcraft where they take the ALEXA metadata that’s included in the HD-SDI feed and they are processing it in real time. I know that Transvideo gets metadata out of the HD-SDI stream and they are displaying it on their monitors, along with graphical depth of field read-outs. Metadata has always been a chicken and an egg situation, as you know. You’ve talked about metadata for decades. We thought if we provided it as widely as possible, somebody will find an application for it. And we’re seeing that slowly happening.

 

How does the Codex Data Logger One external metadata recorder attach?


Henning: Codex Data Logger One is aiming for people who are not delivering their metadata through the camera. They are thinking about this as a postproduction center along with the Vault that’s getting the image and the data from other lenses. You can marry everything in the Vault and prepare that for further deliverables in editing and copies and proxies and also export it into databases. So Codex is more system driven, able to handle a huge amount of data and also different camera types. [The CodexData Logger One also captures additional information such as inertial data and GPS. It supports /i Squared, is integrated with other devices such as Preston and provides consistency across cameras and lenses.]

 

Marc: You might not need that with an ALEXA because data is integrated on the ALEXA. But let’s say, gasp, you use a non-ALEXA camera. You could use the Data Logger box with a camera that doesn’t have the ability to capture the lens data inside the camera. With the ALEXA we’re trying to integrate everything. The LDS capture is integrated in the camera. We’re capturing all the camera information. And with the Plus camera, even the remote control ability is built into the camera so you don’t have to attach extra boxes. With other cameras you may need an external box to record the lens data and then you need another external box for wireless follow focus. With the ALEXA XT Plus, for instance, all that is already integrated into the camera so you have fewer boxes, fewer cables and fewer breakdowns.

 

If you’re archiving to LTO does the metadata go along with it as well?


Henning: Yes.With ARRIRAW, the metadata is in the ARRIRAW header, and it stays there. Last week we published the ARRIRAW DPX multi chunk header description [which was developed by Codex]. Before that, DPX files were a big problem because, although they were a standard in the industry, there was no standard to put metadata in DPX. We created a chunk header which actually copies the entireARRI header into the DPX file and makes a description so that, for example, The Foundry (Nuke) and other companies can use it and display the metadata even if the ARRIRAW was converted to DPX by another vendor. If somebody changed the metadata, we can see the original and what was changed. Keep it transparent!

 

For example, let’s say you’re working withthe ARRIRAW file converter and you see a file that was not processed with the800 ASA setting but with the 200 setting for whatever reason. Or someone changed the white balance. The operator can see something is wrong. There was no system with that luxury for the VFX world up to now.

 

I talked to the effects supervisor on LIFE OF PI and he told me how Claudio Miranda, ASC, the DP, might be looking for a scene shot with a 25mm Master Prime. So they looked in their database for all the occurrences of 25 mm Master Prime shots and they found it very quickly. This is a tool that can really help the visual effects people – an industry not making enough money. LDS and intelligent handling of metadata is something that can help them. It isa boring issue and it is not fancy or sexy, but if you use it intelligently, you can save a lot of money, time and effort in searching and setup.

 

You both know I’m a huge advocate of metadata, but it seems like few are using it to its proper advantage.

 

Marc: It’s coming. Here’s a lovely, recent example. I visited the folks shooting GAME OF THRONES in Ireland.  They’re very interesting because they’re HBO. They’re not be holden to any regular studio sothey kind of came up with their own procedures. They’re using the metadata a lot. They’re shooting with ALEXA onto Codex Recorders. When a digital magazine comes off the Codex they put it in a special Codex Onboard M in the post suite that has its recording disabled. They go through it and they make sure all the metadata is correct. They’ve found that if any metadata right at the beginning is wrong, it will propagate throughout all the deliverables, all the proxies,and then you can never fix it, never get it right. So before they do anything else, even before they do a backup, they check metadata. I’ve never seen this before—actually making sure the metadata is correct as the very first step.

 

[Because they use Codex, they can take advantage of the dynamic metadata capability of the Codex Virtual File System(VFS). The VFS is a part of all Codex products: one of its benefits is that metadata can be viewed and edited.]

 

Then they do the backups with the correct metadata, do the dailies, and then everything else follows from there. This shows how important metadata isto their workflow.

 

Many productions are editing with Avid, conforming ARRIRAW as DPX files and then color correcting DPX files.Are you using DPX files as well at ARRI Film & TV?


Henning: We’re doing DPX also. Sometimes clients have gone to Open EXR – more visual effects driven companies. We have to say that we get very, very good color correction results from the DPX format, which means that one does the ARRIRAW processing before conform and grading. So there’s actually no need to debayer live during color grading. You can do that, but you get the same result, in our opinion, when you first convert to a DPX file and then color correct from there—because you’re ending up both ways in the same Log C wide gamut color space and grade based on this, hopefully using a Look Up Table.

 

But you’re throwing out metadata at that color grading stage?

 

Henning: When we have integrated output to DPX with metadata it would not be lost. The most important thing is that the processing is done with the right white balance anda right exposure index. This is directly out of the ARRIRAW file. Then you go into the DPX file which only contains the preprocessed image for the color timing.

 

Wouldn’t it be good for metadata to go all the way through to grading? The DP is in the DI grading suite and can’t find the meticulous notes jotted down for Scene 105, Take 6. It was supposed to be a little warmer with a little help to pull down the sky. The camera reports can’t be found.


Marc: I think you’re right. However, I see a new trend now, which is to do color on the set. I traveled the U.S. this year and went to a number of sets, including X-MEN and GODZILLA. On all these shows the DIT was acting like a colorist on the set. The DP would constantly tweak the image to get essentially a color corrected image on the set, or at least a preview color correction. The CDL would then go with the footage for the dailies creation, and would be applied so that the dailies had the same color correction as they were seeing on the set. They would also sometimes use that CDL as a basis for the final grading. I’ve seen this in two versions. Versionone is you just do the primaries on the set; that goes into CDL, travels todailies, travels to the final grading. And there’s a second version, which I’ve seen on some of the high-end feature films. The DP would go into a special trailer at the end of the day to do color grading with primaries, secondaries and power windows, even render out the DPXs so the special effects people would get proxy DPXs that already have the color timing the DP wants. When they do their special effects they already know what the end result really is going tobe. I’ve heard a lot of DPs say that they’re not invited to final color grading sessions or they don’t have enough time and so they’re trying to do as much as they can on the set now.

 

That’s a very good point, especially if you’re not invited or don’t have time or are working on another show.

 

Marc: The result is they’re grading on the set now. There’s so much of it that the DIT has become the on-set grader for a lot of people. We’re supporting that with the XT camera in that you can actually load the CDL from the DIT’s laptop via an Ethernet connection and attach it to the ARRIRAW file.

 

How is that attached, as metadata or…

 

Henning: We have some space free in the metadata header. We gave the ARRI header specifications to all the partners, including Codex, and they write the information into the ARRIRAW file which goes all the way through until the end.

 

Is this only possible if you’reusing a Vault or can it be done with anything?


Henning: You have to use the Codex virtual file system. It’s not about the Vault hardware box. It is about the Codex virtual file system [which is an integral part of all Codex products].

 

Marc: It works with the Vault, with the single dock if you have a license for the Codex virtual file system, and it works with a dual dock. Those are the three download hardware platforms that would support that.

 

What are the most DITs using for grading on set or near set?


Henning: In my opinion, most of them are using Resolve. It’s a very good system. It’s cost-free. It’s an incredible tool. The Lite version can be downloaded for free. I looked it up today and it does almost the same as the big version. It doesn’t have support for de-noising, stereo 3D, or the big panel, and is limited to UHD. Many of the big guys are using Colorfront OSD. It is a very common tool, although the strength of Colorfront is actually to make the deliverables and dailies.

 

Marc: On X-MEN they were using EFilm Color stream software. Other jobs had Pomfort Live Grade. The hardware all the DITs seem to be using is the Blackmagic Design HD-link. Everybody uses that hardware, everybody. There’s different software being used, but everybody has the Blackmagic Design HD Link.

 

Henning: It’s a box and it applies the 3D Look Up Table they have just generated so that it can be shown on the monitors around the set and in the video villages.

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