In many video editing projects, especially for broadcast, the output format will usually be clearly defined. The footage you shoot should ideally comply with the output format to reduce the need for conversion during post-production.
If you’re working on a project today that includes older content from videotape then you need to ensure that the archive footage is acquired in the right format and at the best possible quality. Video from old tapes isn’t the only area of concern. Any video material that you bring in from third party sources might not match your prescribed editing format. e.g. If the library clip you need isn’t available in the correct frame rate or size then it will need to be converted.
In this article we will cover some of the basics of video format and standards conversion and details about the service we provide. It’s quite a technical subject so some understanding of the terminology will be required but we will do our best to stick to plain English.
Aspect ratio conversion (ARC)
If your current edit is destined for broadcast, online or DVD/Blu-ray distribution then you’ll almost certainly be working in 16:9 widescreen format. When you need to include 4:3 content a decision has to be made about how to present it within the widescreen frame.
The options include pillar boxing which leaves blank areas each side of the image, zooming into the image so that it fills the width of the frame but crops off part of the top and bottom of the original image (also called cropping) or applying a smart stretch which retains the central section of the image but gradually expands the edges to fill the wider frame. All three standard options are a compromise of sorts. There is another “trick” which can be employed in post production where the pillar boxed image is laid over a stretched/blurred version of itself – this can be effective in certain applications.
Some projects demand much more critical aspect ratio conversion (ARC). i.e. A crop is desirable but the producer needs to assess the footage on a scene by scene basis to determine which area of the frame is most important and therefore which bit (or bits) to crop off.
Upscaling and cross conversion
When you want to include SD in an HD project then you will need to enlarge the content to fill the new HD frame size. The upscaling process may also be combined with aspect ratio conversion.
Most editing software will have some basic upscaling built-in but it can be caught out in some instances. Incorrectly interpreting the field order of interlaced sources is not uncommon. Hardware upscaling at the digitising stage ensures that the footage is captured in exactly the right flavour of HD for your project.
Even if your project is all HD it could include a mixture of progressive and interlaced content from different sources. Your video editing software might appear to allow any mix of HD formats but the output might suffer if the software conversion isn’t up to scratch. Most of us have seen field order problems that only seem to reveal themselves after the final render.
Video frame rate conversion
A good number of video editing applications appear to be able to handle multiple frame rates without issue. It will quite happily let you mix non-compliant frame rates into the edit and export to pretty much any frame rate or size. The trouble is that the end result is often sub-standard. The non-compliant bits of the edit can stand out like a sore thumb.
Good quality frame rate conversion is technically very difficult to achieve. If you’re doing aspect ratio conversion and upscaling then you really need to use the right solution. Standard video editing software will not be good enough.
Input and output – getting it right
Hopefully all of the above makes sense and explains why good quality scaling, standards and aspect ratio conversion at the input stage (prior to editing) is critical to maintaining quality. The same is also true at the output stage. The requirements for broadcasters can vary, even in the same region. A version of your 1080i/25 project may be requested in anamorphic 480i. Most standard editing software will let you punch in the settings but the file it produces will almost always be rubbish if you actually look at it on a NTSC CRT display.
We’ve made it our business to do good quality standards conversion in hardware and software. Depending on the job we will use broadcast grade hardware or a proven software solution. We do up/down and cross conversion recording directly to Apple ProRes, Avid DnX HD, Blackmagic or Matrox Quicktime or AVI files (compressed or uncompressed). Software conversions are available for some file-based workflows.
Teranex 2D from Blackmagic Design is our hardware video standards converter of choice. The Teranex units are broadcast grade and offer superb quality with excellent noise reduction and a variety of conversion options. Although the unit is hardware based we can use it for hybrid file based conversions. i.e. We can play out a file to the Teranex unit via Thunderbolt and record it to an HD-SDI HDD deck or NLE.
Canopus ProCoder is another of our goto products. This software solution has a proven track record of delivering very high quality standards conversion of file based media. It’s especially good at downconversion and frame rate conversion. We don’t use it for upscaling because the Teranex is much better.
We have HD and SD monitoring including PAL and NTSC capable CRT displays for checking interlaced SD content. Our studio is equipped with various legacy formats including BetacamSP, SX, U-matic, DVCAM and most domestic analogue and digital videotape formats.
The days of straightforward PAL to NTSC standards conversion are long gone. Even on fully digital online projects we are seeing the need for good quality file conversion. Some systems stick to very rigid file formats e.g. Playout systems on some aircraft will only accept 480P anamorphic 23.97fps at 15Mbit/s. If your content is 1080i/25 then the conversion will need to be spot on in order to make sure the file is going work and be of optimal quality for that delivery platform.
If you’re looking for a UK based company to take care of your video format and standards conversions then give us a call. We’ll be happy to listen to your requirements and discuss solutions.