Frame Shifting or Blanking Shift Issue Unveiled

 

Introduction

Precision and quality are supreme in the realm of video content. Any disruption to the seamless viewing experience can detract from the intended message and artistic expression. One persistent issue that hampers the quality of experience is the elusive “Frame Shifting” or “Blanking Shift”. In this article, we will explore the ins and outs of frame shifting, its impact, and the crucial role of Video Quality Control software in mitigating and resolving this challenge.

Understanding Frame Shifting

Frame shifting, also known as blanking shift, is a technical anomaly where the active image within the video frames has intermittent horizontal and/or vertical displacement. This issue manifests as a distortion in the height/position of the letterbox or the width/position of the pillar box areas within the frame.

The active image represents the central portion of the video excluding the black bars on the sides, such as letterbox or pillar box bars. The central content area is what viewers focus on, and it may be surrounded by black bars on the sides which maintain the intended aspect ratio of the video, ensuring it displays correctly on screens with different dimensions. However, when frame shifting occurs, the active image appears to move or jump across the frames unpredictably creating an abrupt disruption in the viewing experience.

Frame Shifting can significantly impact the quality of the video and may be disorienting for the viewers. It’s important to note that Frame Shifting is usually not a part of the creative intent; rather, it is an unintentional technical flaw. To address this issue, meticulous attention to detail is required at editing stage to maintain the integrity and professional quality of the video content.

Frame alignment plays a crucial role in mitigating the effects of frame shifting during editing. By ensuring precise alignment of the active image within video frames, frame shifting-related distortions, such as mispositioned letterbox or pillar box areas, can be minimized or eliminated. Proper frame alignment helps maintain the intended aspect ratio, eliminates visual disruptions, and provides a seamless viewing experience for the audience.

The issue must also be validated during the QC stage before content is delivered to the next stage.

Below are the images showing frame shifting:-

Impacts of Frame Shifting on Video Quality

Visual Disturbance and Impact on Creative Intent and Storytelling

Intense Frame Shifting may lead to significant visual disturbance during playback. Abrupt movements of the active image can disorient viewers and disrupt visual storytelling, diverting attention to quality issues instead of the intended narrative and hindering the flow of the story.

Image Misalignment

Frame Shifting leads to misalignment of the visual content within the frame. It prevents the frame from completely filling the intended active image area.

Precision and Consistency

Frame Shifting directly affects the precision and consistency of the video. It compromises the accuracy and alignment of the frames, resulting in a loss of quality and diminishing the overall professional appearance of the video asset.

Causes of Frame Shifting

1.    Editing Errors: Frame shifting can occur during the editing process due to various reasons. One of the causes is mistakes in editing techniques, specifically related to the alignment and placement of the active image within the frame. Unintentional alterations to properties like position can result in frame shifting, causing the active image to shift within the frame. 

2.    Aspect Ratio Conversion: Incorrect or inconsistent aspect ratio conversion during editing can cause frame shifting. If resizing is not executed accurately, it can disrupt the positioning of the active image.

3.    Cropping and Resizing Issues: Improper cropping or resizing of video content can result in frame shifting. Any misalignment during these processes can lead to an unintended shift of the active image.

4.    Transitions Between Videos: Frame shifting may occur when transitioning between different video sources with varying aspect ratios, if these transitions are not handled seamlessly. Sudden changes in aspect ratios can disrupt the consistency of the active image.

 

The Role of Media QC Software: A Solution for the Frame Shifting Issue

In the fast-paced world of video production, manually identifying and rectifying “Blanking Shift” or “Frame Shifting” problems can be arduous and time-consuming. One must meticulously inspect the entire sequence of frames to ensure they were rendered and replaced correctly. Any incorrectly placed or rendered frames need to be corrected to fix the Blanking Shift.

This is where Video Quality Control software such as Pulsar  and Quasar comes to the rescue. They are designed to automatically detect Blanking Shift (or Frame Shift) and a wide range of other quality issues in video content. It automatically scans the video for anomalies, ensuring that the active image remains consistent throughout the content. By employing an automated QC software, media professionals can streamline their quality control processes, saving time and resources, and ensuring a seamless viewing experience for their audiences.

 

Conclusion

Blanking Shift is a technical issue that significantly impacts the quality and viewer experience of video content. Preventing and addressing this issue requires precision during the editing process and the use of reliable Media QC software such as Pulsar/Quasar.. By actively identifying and rectifying Blanking Shift, content creators and distributors can ensure their videos are technically sound, maintaining the artistic integrity of their work and providing audiences with a distraction-free viewing experience.

 Originally Published at:- https://www.veneratech.com/

Dialog-gated Audio loudness and why it is important

 

Introduction  

Being a fan of watching video content on a variety of devices, I sometimes get into situations where I can’t make out what is being spoken even though the overall audio levels are fine. Have you experienced these issues? I am sure they are annoying enough and make us think how this content was approved for publishing with such obvious issues.

Many of you would be surprised that such content can pass the Loudness criteria that are commonly used for typical audio QC testing, and if not manually reviewed, the content can indeed pass and be made available to consumers. This is because a more sophisticated level of Loudness testing, called ‘dialog-gated loudness’ criteria must be used in order to verify that the portion of the content with dialog has the proper loudness levels.  Not performing the dialog-gated loudness verification could result in content that while passing general Loudness criteria, may still not have audible dialogs for the viewer. This can negatively impact content providers who are continuously vying to gain & retain consumers by maintaining the high quality of their content – both technically and editorially. Now a days OTT service providers like Netflix and others require the dialog-gated loudness compliance.

In this article, we will discuss how such issues can be detected by using Dialog-gating and how our QC products can help content providers achieve this in a fully automated manner.

Dialog Gating

Gating is the process that only pass audio signal satisfying the criteria while removing the unwanted audio signals from loudness measurement. The gating criteria may be absolute audio level, relative audio level or audio type such as speech or non-speech.

Dialog-gating is a process that only allows the audio signal which has speech content. All other non-speech audio segments are rejected and not passed through for the loudness measurement.

Level-gating is a process that only allows the audio signal higher than particular audio level to pass through. There are two common level gating techniques:-

·         Absolute Gate. All the audio segments below a particular audio level (mostly -70 LKFS/LUFS) are rejected.

·         Relative Gate. All the audio segments that are lower than particular value (mostly 10 LU) below the average absolute loudness are rejected.

Let’s consider the case of a 5.1 audio stream. The list of channels in such audio stream are L, R, C, Ls, Rs, Lfe. Normally the speech content is carried in the Center (C) channel but sometimes it may be carried in Left (L) and Right (R) channels also. For this reason, only L, R and C are considered for calculating the Dialog-gated loudness and all other channels are ignored.

In real workflows requiring dialog-gated loudness measurement, an adaptive gating approach is taken. It means that Dialog-gated measurement should be performed if there is sufficient speech content in audio. If the speech content is not sufficient, then level gating is used to perform the loudness measurement.

The diagram below shows such a workflow for a 5.1 audio stream:

The upper half of this diagram takes the audio content from L, R and C channels for dialog-gated loudness measurement. The content is passed through “Dialogue Intelligence” to determine if the audio contains speech. If the audio has speech, it is assigned a gain of one, else zero. The resultant channels with gain are fed to the dialog gating process. In this case, only the audio segments containing speech will pass through along with corresponding loudness level and amount of speech content. Non-speech audio segments will be dropped. Adaptive gate selection decides whether to use dialog gated loudness or level gated loudness depending on the overall amount of speech content.

This measurement provides a true picture of actual speech levels in audio and content providers can be sure that the audio experience of their audience is preserved.

Venera’s Automated QC tools – Pulsar™ & Quasar® allows automated measurement of dialog-gated loudness measurement. Following options – shown for the EBU mode (popular standard in Europe) – are available in both the solutions:

 

These options are available for ATSC (popular standard in North America), OP-59 (popular standard in Australia), and ARIB TR-B32 (popular standard in Japan) modes as well.

In addition to measuring the dialog-gated loudness, users can also measure the difference of loudness level using dialog-gated measurement and level-gated measurement. This gives them a practical perspective of audio composition in the content they provide to their consumers.

Pulsar™ also allows users to automatically normalize the audio levels eliminating manual intervention in making the content compliant.

In addition to Loudness measurement, Venera’s QC tools – Quasar® & Pulsar™, offer a wide range of Audio and Video measurements that help users automate the otherwise tedious content QC operations.

Quasar® is a Native Cloud Content QC service, allowing auto scaling with ability to process hundreds of files simultaneously with wide range of content security capabilities so that our users can process their content with peace of mind. Quasar® can be integrated using REST API for highly automated workflows. Visit quasar to read more about Quasar® and request a free trial.

Pulsar™ is an on-premise Automated File QC systems, allowing scaling with clustering of multiple Verification Units in user’s datacenter or office location. Pulsar™ is the fastest QC system in the market allowing up to 6x faster than real-time speed for HD content. Pulsar™ can be integrated using XML/SOAP API for highly automated workflows. Visit pulsar to read more about Pulsar™ and request a free trial.

Get in touch with us today and we would be happy to discuss with you how we can help solve your content QC challenges efficiently!

 Originally Published at:- Dialog-gated Audio loudness and why it is important