Because today’s broadcast workflows are file-based, the human eye is insufficient to make signal quality assessments. It is no longer adequate to simply watch a monitor and give a quick audio check to ensure your viewers and advertisers are getting the quality they paid for. Today's signals require a software-based quality check (QC) test system.
With the introduction of compression technologies such as MPEG-2, H.264 and other derivatives, operators and engineers can no longer depend on just their eyes and ears to know if the incoming or outgoing signals are legal, of the correct language, complete with captions, ect. In addition, with the trend to playout out multiple channels from one control center, the chance for errors multiply.
Now add new delivery technologies; OTA, DTH, IPTV, Mobile TV and VOD and formats; SD, HD, UHD 4K and the task of ensuring proper delivery of high-quality signals to multiple audiences quickly becomes a nightmare of needed checks and tests.
Each type of signal, format and standard creates its own set of test and QC challenges. This is often the case where ingest must handle multiple formats. Such operational requirements must be met head on to be sure viewers receive the proper content in the quality for which they subscribe. Let’s examine an input to output workflow that can help manage these challenges.
Ingest is the first step. Some workflows simply move the content in its received format into a temporary archive. Later, perhaps at a slow-pace time, the material can be validated before it is further processed. Should the incoming material arrive near air-time, it can be fully processed and checked along with ingest.
No matter the time criteria, both procedures have intermediate steps that may be error prone and can potentially introduce errors in the content. Such errors may mean unhappy viewers, or even more serious, a violation of a service level agreement (SLA).
Until recently, broadcasters often developed their own manual solutions to content verification. But with the increased complexity and the volume of content, those practices seldom are practical.
Manual verification imposes the following constraints:
- Manual testing is error prone and audio/video errors can be easily missed just by blinking or loss of concentration on the part of tester.
- The errors found depend highly with the skill and experience of testers and the amount of time they have to make the required checks.
- Digital streams are not subject to visual checks. Even the best engineer or operator cannot examine a string of ones and zeros to determine if the correct compression has been applied or that the audio channels have not been swapped.
The solution is to automate the QC process and use a system and technology that can be applied at multiple points in the broadcast chain. The figure below shows a typical broadcasting setup:
Once a digital workflow has been established, it becomes easier to determine where and what checks need to be made. They can be spread through the entire chain. Image courtesy Venera Technologies
The signal flow can be further divided into smaller workflows, each of which caters to specific needs. For discussion purposes, we will examine three main workflows and the corresponding verification needs.
Ingest to Playout
Content typically arrives from multiple sources and often in several formats. This example workflow describes some high-level QC steps that can be made and cover the process from ingest to playout.
Content is ingested in a high quality format. Any format or signal conversion needed can be handled later in the playout process.
Before and after checks
In this example, the content is checked both as an incoming signal and again after conversion just prior to playout. Typical checks at the ingest stage might include checks for black frames, frozen frames, silence. A proper QC solution should also detect faults which may have been introduced during repurposing. Some of these faults could include blockiness and codec compliance errors. Verification could also include values for specific audio/video parameters such as aspect ratio, Profile/Level etc.
This two-step check will immediately isolate the source of any errors between ingest and just prior to playout. Image courtesy Venera Technologies
Ingest to Archive
Content may arrive anywhere between hours and days or weeks prior to it being needed for playout. This means it needs to be archived until time for playout. If QC checks are delayed until playout, it’s likely too late for a refeed or replacement file.
Content errors need to be identified at the ingest stage. If an error is detected while the content is being retrieved from archive for playout, there is no opportunity to correct the problem. In addition, if the error is detected upon retrieving from the archive, it is not possible to know whether the original file was defective or if something failed in the archive process.
In this example workflow, the content is ingested and first moved to short-term storage and then onto long-term storage, depending on the playout schedule. The archiving process is typically controlled by specialized archiving systems.
A variety of audio/video errors can be introduced during the archiving process, both while moving to short-term and long-term storage. Example errors typically include black frames, colored frames, silence, loss of audio. A workflow-based QC system can monitor the content at both these stages to ensure that any errors in the content are reported immediately so that the user can take the appropriate actions.
Multiple points of QC are made in this example, which enable errors and the source of error to be detected and immediately reported to operators. Image courtesy Venera Technologies
Archive to Playout
As the content moves closer to playout,it is retrieved from storage and played out under the control of automation. The signal passes through multiple stages, any of which can potentially introduce errors.
If the content is moved to the short-term storage then errors may be introduced during this stage. If the content requires repurposing into a specified format, then again faults related to quality or format compliance may be introduced into the content. A proper QC monitoring solution can examine blockiness, codec conformance, parameter value validation etc. Some QC systems support custom tests enabling a station to add even more protection to its quality playback.
The following figure shows a typical workflow from Archiving to Playout:
QC is applied here when the content reaches the short-term archive and once again just prior to playout. Image courtesy Venera Technologies
Implement a total solution
It makes little sense to settle for a limited set of spot checks when building a facility-wide QC system. Select an efficient verification solution, one with the following capabilities:
- Supports custom rules/profiles/templates that can be applied to a particular verification process. Different verification rules can be used at different points in the workflow depending on the QC process required.
- Sophisticated application that is easy-to-use. It should offer a clear and uncluttered reporting structure providing, which can be customized to highlight only the checks required.
- Ability to automatically and simultaneously pick up the content from multiple locations corresponding to different stages in the workflow.
- Feature set to span a wide variety of quality and parameter checks for audio and video streams.
- Highly reliable and robust system that can be used for 24×7 operations in any broadcasting environment.
- The system should offer faster than real-time performance to maximize throughput. Look for the ability to ‘gang’ systems in master/slave configurations. This will allow broadcasters to expand the system to accommodate growing volumes of content.
- Look for a solution that offers rich reporting capabilities including reports and alerts so that appropriate actions can be taken in a timely manner.
- Ability to co-exist in the existing workflow system providing a uniform experience to the users. You should not have to rebuild your workflow to accommodate a system-wide QC solution.
- Web based multi-user interface for remote and local management.
Today’s broadcasters are challenged by a variety of formats, signals and standards. The best way to ensure that viewers and advertisers receive what they pay for is to rely on a versatile and sophisticated system-wide QC monitoring solution.
Note: This article is based on a PDF white paper from Venera Technologies.