By Paul Robinson, Tektronix
The lights come on and the CEO glides on stage to launch a new product. Everything goes smoothly, the audience is wowed, and the product goes on to great success. That’s the formula Steve Jobs applied time and again, making it look easy. But behind the scenes, the former Apple co-founder and CEO was known for working tirelessly to refine content and rehearse his lines. The result of all this preparation were some of the greatest product launches in tech history.
The same lesson applies to many other industries, and the broadcast and cable industries are no exception. If you want to have flawless content delivery, it all starts with “content readiness.” This means having all your content available in a form and condition suitable for distribution. It means content that’s not only free from objectionable distortions, but also equipped with the right markers, metadata and resolution to deliver the best possible service to subscribers, regardless of the receiving platform.
This level of content readiness calls for a rigorous quality control (QC) program that inspects every individual file—from a 15-second ad to an HD movie—as it enters the facility where it is stored for eventual play out. Almost like a law of physics, the challenge of quality control seems to grow with the square of content quantity.
Perhaps there was a time when visual inspection of incoming programs was sufficient, but that era ended with the explosion of content required for services like video on demand (VOD) or adaptive bit rate streaming. Below are three areas where we often see video providers fall short in terms of ensuring content readiness.
VOD Content Readiness
Subscribers pay for the VOD product and they expect a reliable, seamless quality. The quality of the content stored in the VOD servers is crucial to the success of the whole process. The moment when the requested content exits the facility is clearly not the right time to evaluate its quality.
Incoming VOD assets should undergo QC checks when they are received at the ingest cache, or while they are stored on the VOD servers. What kind of problems should you be looking for? Here are the most common:
File integrity problems: These can occur during the automated pitching-catching process at ingest. Files can become corrupted or truncated. Is the file decodable throughout and is the play time correct?
Format compliance issues: Files must be checked for compliance with specifications, such as OpenCable™ CEP 3.0 (Content Encoding Profiles). Do the bit rates follow the recommendations? Are the PID numbers correct (e.g. 481 for video or 482 for audio)? Are the GOP lengths correct?
Regulatory issues: Does the VOD material comply with governmental regulations? Are the mandated CEA 608/708 captions present? Is the audio loudness CALM Act compliant? In every case these characteristics must be not only checked but also corrected when errors are found.
Metadata issues: Does the machine-readable metadata agree with measured values, such as frame rate, displayed picture size, and play time?
Ad Insertion Content Readiness
Ads can be a common source of problems in ensuring content readiness. An initial first step should filter out ads that don’t meet minimum standards, for example having a very low bit rate and consequently poor picture quality, as candidates for rejection. Gross errors in play time (for example a 32-second spot for a 30-second timeslot) are another disqualifier. Other flaws, such as loudness violations, may be accepted with the understanding that the operator will correct them.
The majority of errors associated with ad insertion are quality-related. A local merchant simply can’t afford the lavish production values of a big national campaign, so compromises are made. A small video house might not have a loudness meter, for example. Or perhaps an inexperienced hand produced graphics with garish, attention-grabbing colors that just happen to be out of gamut. Or there may be over-compression, causing blockiness and artifacts. Figure 1 shows an example of a blown out gamut violation.
Clearly, there are many pitfalls and it’s crucial to have a QC regime that can detect these flaws. Another job for the QC system is to confirm that the ad content meets submission guidelines. Many operators constrain the delivery formats they will accept, with the intent of reducing complexity. Limitations may include codec type, container type, audio channel assignments, picture size, bit rate, frame rate and more.
One of the most bothersome errors in ad content is the format mismatch. For example, ads may be submitted in 4:3 standard definition (again the result of cost-cutting production) even though the broadcast will be in HD. One way to avoid it is to set up separate ingest paths for SD and HD deliveries. In addition, the QC tool should routinely verify that the video fills the active image and that letter-boxing/pillar-boxing effects are not a permanent part of the file. And it is becoming common practice to check the Active Format Descriptor (AFD) to confirm that the playout code is correct.
Adaptive Bit Rate Content Readiness
Content distribution used to be straightforward, with scheduled programming going out to subscribers in a controlled environment. But that market has changed forever. Now there are tablets, phablets, phones, laptops and PCs. To be competitive, broadcasters and video providers must offer streaming services for all these devices using Adaptive Bit Rate (ABR) streaming and Over-the-Top (OTT) delivery.
HTTP Live Streaming (HLS) and Smooth Streaming are two of the leading streaming architectures in use today. Both HLS and Smooth Streaming rely on transcoding each asset to multiple bit rates. Thus there are several coexisting versions of each asset.
A key step is to verify the content’s readiness for segmenting. It is important to establish early on that the file can be correctly divided into usable segments. At QC time, the task is one of ensuring that smooth segmentation is possible.
In this context, “content readiness” implies that the Instantaneous Decoding Refresh (IDR) frames, which mark the boundaries between segments, are embedded at regular timing intervals (see Figure 2). The QC checks should confirm that stored content—whether movies or commercials—has the IDRs in place and timed correctly.
Another quality check relates to picture quality in an environment where content is stored in numerous versions, each with a separate bit rate. Are the lowest bit rates still delivering acceptable picture quality? For that matter, are all of the rates providing the expected image quality? This is a test that is not practical to perform on every piece of content in real-time; instead it is best used to guide efficient workflow design. Using a picture quality analysis system, it is possible to fine-tune encoder performance to get the most out of each bit rate. In H.264 compressed video, for example, there are numerous settings that can be adjusted to maximize the final picture quality on the receiving device.
While there is never a guarantee that all content will play out flawlessly every time, following best practices for content readiness will ensure that your viewers have the best experience possible more often then not.
About the author:
CTO, Tektronix Video Product Line
Paul Robinson is a 29-year veteran of the test and measurement industry. In his current role, Paul is CTO for
Tektronix’ Video Test Business focused on developing test, measurement and monitoring solutions aimed at the enabling the deployment of Digital Television, and helping to bring IP Video products and services to market.
Paul joined Tektronix in 1986 as an Applications Engineer and has held a wide variety of senior roles within the company, both in Europe and the US. Paul started his professional career in the Broadcast Industry and prior to joining Tektronix, he worked for the BBC as Senior Systems Engineer. Paul has a B.Sc. in Applied Physics and a DUniv from Buckinghamshire New University.
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