Unfortunately Professional Broadcast Video Production is not as easy as uploading a video from your iPhone to your YouTube account. Creating a quality program for broadcast television is extremely detailed and technical, which requires thousands of dollars of high tech equipment and many years of experience to ensure each facet of the process is completed with the highest level of quality and skill. Below are five easy ways to (not) screw up your video. Hopefully you can keep these tips in mind the next time you hit ‘Export’ and therefore improve the quality of your next broadcast.
#1: Keep it Native
Quality loss can come in many forms and can be even worse with digital video than the traditional ‘Generation Loss’ from dubbing tape to tape if not done correctly. A big mantra here at Aberdeen is to “Keep it Native”. This means maintaining the same format and specifications from shooting through Post to the final deliverable. Taking care to make sure you keep the highest level of quality through each step of the Production and Post processes will ensure there is minimal degradation on the finished program.
It all starts in the camera. It is ‘best practice’ to choose the appropriate resolution and aspect ratio that best fits the highest level of current (and possibly future) broadcast outlets. Usually these days this means choosing the right HD format and maintaining that 1080 or 720 resolution and fielding throughout the post process. Once the content is acquired in the desired format, the next step is to get the assets into your editing system without quality loss. The brand of recording/editing equipment that is in place will dictate which codecs should be used. Remain true to our “Native” mantra by keeping the Frame Rate, Field Order, and Resolution the same as the acquired format no matter the codec. This will ensure the highest quality finished product.
#2: Mixed Media on the Same Timeline/Sequence
Field Dominance issues are one of the most common problems we see at Aberdeen these days.
With a lot of legacy footage shot in Standard Definition (SD) and the increased adoption to High Definition (HD) cameras it is very common to see both SD and HD originated content in the same program. Fielding issues arise because SD footage can commonly be lower field dominant whereas HD footage is only upperfield or progressive. This field priority discrepancy can cause a playback issue because the SD footage (often lowerfield) needs to be played in the opposite field order as HD content. Today’s NLE exports are based on the sequence settings, not the individual clip settings. Two clips with opposite field orders on the same sequence will almost guarantee one of them will look poor on export. It is the editor’s job to correctly convert each clip to the same field order of the sequence or there will be motion and resolution issues with the incorrectly exported video. Ghosting, flicker and motion judder are all signs of incorrect or incompatible field order of the baseband video. This issue is often overlooked as LCD monitors have replaced the older, more expensive interlaced CRT monitors. LCDs use a progressive scan technology that will not accurately display your interlaced footage like a CRT will.
#3: Centercut Safe HD
Every HD station/network broadcasts simultaneously both a HD and a SD signal from a single source video element (commercial, promo, feature, etc). If the originating source video is SD then the simultaneous HD feed will upconvert the SD source (usually adding pillar bars to the sides of the 4×3 video) for the HD viewers. For HD source elements the station’s SD feed will get an automatic downconvert of the originating HD format for their SD feed. Here’s where the issue comes up. Stations want their SD viewers to see a 4×3 full screen program, not letterbox content. To that end all HD source programs are automatically downconverted by center-cutting the HD source for the SD feed. This means that any graphics or visual content outside of the 4×3 raster will be cut off. This process should be considered when creating and positioning HD graphics. Incorrectly positioned graphics (outside the 4×3 raster) end up being a commonly overlooked issue that can result in the program being rejected by the station or airing with cutoff content on 4×3 TVs because the HD program graphics are not centercut safe for the network’s downconverted SD signal.
#4: Broadcast Legal Chroma/Luma/Gamut
Television stations still mandate strict values for Chroma, Luma and RGB Gamut. Today’s cameras are not restricted to the color and brightness values that are required by these television broadcasters. In order to have your program accepted by the station’s ingest operators, it is essential to utilize the NTCS/Broadcast Safe filters available on every NLE system. Generally using the ‘Most Conservative’ preset with no values over 100, will correctly adjust the hot signals that modern cameras capture.
#5: Audio Peaks and Loudness
Recording and mixing digital audio to the 0dB level is far too strong. Broadcast outlets will not accept anything so “hot”. Here’s why: Once an audio signal passes the 0dB threshold the signal can no longer be captured. This is referred to as “clipping”. There is no regaining the lost audio information resulting from clipping. To prevent this issue it is best practice to not drive the audio to the 0dB limit. Digital headroom is the term used to signify that the audio peak level has been lowered below the 0dB point. Usually broadcasters recommend at least 6dB of headroom to prevent their broadcasts from clipping. This means that the program peaks should not meter/register above -6dB.
*Engineer’s Best Tip: Audio “loudness” is now being monitored closely thanks to a US Congressional law (The Calm Act) which now mandates US broadcasters comply with the ATSC A/85 audio standard of
-24LKFS +/- 2dB. In our analysis of 25,000 files, more than 90% of programs that had audio peaks mixed to between -8 and -10dB had a loudness measurement that was inside this -24LKFS +/-2 dB legal range. This is an easy ballpark indicator to know you should be in or very close to compliance of this new mandatory standard.