在教室里拍摄4K视频:有什么要紧的?

高等教育, the pressure to deliver at anything higher than 720p doesn’t come from students, who are far more likely to stream their curricular video to personal mobile devices than to a communal UHD TV set. 如果我们要跳跃到一个显著更高的记录分辨率, our justification cannot depend on preventing continuity errors at the same level as for entertainment video, so let’s explore some justifications for shooting in 4K while delivering at lower, 为移动设备设计的决议.

Suppose we’re shooting a demonstration where the subject is unpredictable: If there’s a shot where we can’t know precisely where to aim the camera, 那么有四倍的自由框架是有用的. We recently recorded a gymnast performing on a horizontal bar to demonstrate a concept for a mechanical engineering course. 为了尊重学生运动员的时间, we wanted to set up the shots wide enough to accommodate any reasonable contingencies 和 let her get back to her own business as soon as possible. In post, we’d punch in to the framing we would have picked if we’d had multiple takes. 4K画框会提供一个奢华的舒适区.

类似的, 在拍摄实验室镜头时, it wouldn’t be extraordinary for something serendipitous to happen that the presenter would explain off the cuff. At 4K, the camera operator need not even attempt to zoom in on what he guesses is relevant. 4K拍摄, we can “enhance” in post once we’ve discussed with the expert what to show the students, 这样我们就不用冒险了.

Or maybe it’s not the subject’s position that’s unpredictable, but the camera’s. 我们偶尔会在无人机上安装摄像头, where sections of the frame will be sacrificially shot 和 discarded for image stabilization purposes.

即使是对着说话的头拍照, 我们可以以4K拍摄广角，并在后期打孔到所需的框架, simulating a multi-camera shoot by cutting between two zoom levels from the same 4K footage to hide edits.

I find these arguments to be compelling, but my team members have yet to make that leap to 4K. 为什么呢??

首先，根本不存在紧迫性. The difference between HD 和 4K isn’t as dramatic as it is between SD 和 HD. We aren’t changing the shape of the frame, we’re simply recording four dots instead of one. HD footage won’t look intolerably anachronistic; even when we switch to 4K, we’ll occasionally make a mistake when setting focus 和 work from slightly blurry footage. 我的直觉是，在4K的情况下，我们会拍得更深，而不是更大. Most scenarios in educational media production don’t require that depth of resolution.

第二个, I’m not convinced the 4K shooting technology is mature enough to invest in, 相机制造商也显得同样谨慎. 具体地说, there are two video codecs efficient enough to store 4K resolution video at bitrates that suit our existing portable media 和 fileservers: HEVC 和 AV1. HEVC(或H.265)是hd标准编解码器H的继承者.264, 和 boasts the ability to halve the file size without compromising picture quality. It is, however, encumbered with a complicated 和 evolving licensing scheme. AV1 is the successor to the royalty-free VP9 codec (among other projects by Alliance for Open Media participants), 并计划在本期出版时发布.

Camera manufacturers are conspicuously not recording video with these video codecs. 我所知道的唯一能用H拍4K视频的相机.265编解码器都是由三星出售的——或者至少，他们曾经是. CES 2017 came 和 went without a significant announcement about HEVC adoption in cameras, aside from the notably restrained (albeit impressive) features of the Panasonic GH5’s debut firmware.

I’m waiting on the answers the camera manufacturers get to two critical questions: Will AOMedia’s AV1 codec be good enough to adopt over HEVC? 如果不是, will it be good enough to push HEVC’s licensing costs down enough to cover the difference in quality? 我敢打赌，我们可以再等一年才能找到答案.

本文发表于2017年4月/ 5月号 流媒体杂志 《4K:急什么??"