I recently bought an action camera and captured first-person video of a bike ride down a mountain road. I used some basic third-party editing tools to add speed and elevation overlays to the video, and rendered the whole thing as an MPEG-4 (H.264) video: 2704x1521 @ 60 fps.
The video resides on a SSD attached to my router and configured as a media server. The Roku Media Player recognizes it and plays it for a few seconds before stopping with the error: "Excessive AV Skew." I created a second version of the video identical to the first, except with a "quality" setting of 80 instead of 100 (that was the only adjustable parameter). Resolution and frame rate are the same, but the file size is 6.3 GB instead of 9.8 GB. The second version plays for 15-20 seconds before stopping with the same error.
In case it's not apparent, I'm relatively new to video rendering tools. I'm eventually going to make a lower resolution version of the video to share. I just thought I'd start with the native resolution and see what can handle it. My Ultra (4640X) couldn't quite do it, but it was close... maybe close enough to work with a small adjustment?
I am getting this error with media I run off my usb drive. We run it on a loop in our waiting room and have been for months. All of the sudden it started stopping after just a few videos with this error. We have a different Roku tv in the waiting room and the usb drives and files are identical but only one of the TV's are getting the error. All the videos are only 1080p
Thanks @theelbrando for the reply. But it didn't fix the issue for me.
@RokuDanny-R Can you please look into it, any suggestion/help would be appreciated? I am unable to understand this "excessive av skew" error.
This page was listed at the top of my Google search query for "Generic Playback Error excessive av skew". A second search through the Roku Community for "excessive av skew" showed this as the only result as well.
I was simply watching a pro football game last night on the Peacock app when the screen froze with "Generic Playback Error excessive av skew" plastered on it. I simply exited out of the app and restarted it and it went away, but I want to understand why it happened in the first place.
Same issue playing video files from USB, plus video and audio are out of sync. Movie plays for around 5 min before being interrupted by AV Skew message. I press resume and it plays the 1080p clip for another 5 or so minutes before again being interrupted.
Can you please provide more information about the issue you are experiencing? What are the steps to reproduce this issue? Does this only happen on a specific channel or content? Can you provide a screenshot of the issue you are experiencing?
In the preceding chapters we got acquainted with the linear model as an extremely flexible tool to represent dependencies between predictors and outcome variables. We saw how factors and covariates gracefully work together and how complex research designs can be captured by multi-level random effects. It was all about specifying an appropriate (and often sophisticated) right-hand side of the regression formula, the predictor term. In contrast, little space has been dedicated to the outcome variables, except that sometimes we used log-transformed outcomes to accommodate the Gaussian error term. That is now going to change, and we will start by examining the assumptions that are associated with the outcome variable.
A particular question is probably lurking in the minds of readers with classic statistics training: What happened to the process of checking assumptions on ANOVA (and alike) and where are all the neat tests that supposedly check for Normality, constant variance and such? The Gaussian linear model, which we used throughout 4 and 6, shares these assumptions, the three crucial assumptions being:
In the next section we will review these assumptions and lead them ad absurdum. Simply put, with real world outcome measures there is no such thing as Gaussian distribution and true linearity. Checking assumptions on a model that you know is inappropriate, seems a futile exercise, unless better alternatives are available, and that is the case: with Generalized Linear Models (GLMs) we extend our regression modeling framework once again, this time focusing on the outcome variables and their shape of randomness.
The GLM framework rests on two extensions that bring us a huge step closer to our precious data. The first one is the link function a mathematical trick that establishes linearity in many situations. The second is to select a shape of randomness that matches the type of outcome variable, and removes the difficult assumption of constant variance. After we established the elements of the GLM framework 7.1, I will introduce a good dozen of model families, that leaves little reason to ever fall back to the Gaussian distributions and data transformations, let alone unintelligible non-parametric procedures. As we will see, there almost always is a clear choice right at the beginning that largely depends on the properties of the response variable, for example:
These two GLM families have been around for more many decades in statistical practice, and they just found a new home under the GLM umbrella. For some other types of outcome variables good default models have been lacking, such as rating scale responses and time-on-task and reaction times. Luckily, with recent developments in Bayesian regression engines the choice of random distributions has become much broader and now also covers distribution families that are suited for these very common types of measures. For RT and ToT, I will suggest exponentially-modified Gaussian (ExGauss) models or, to some extent, Gamma models. For rating scales, where responses fall into a few ordered categories, ordinal logistic regression is a generally accepted approach, but for (quasi)continuous rating scales I will introduce a rather novel approach, Beta regression.
Too many choices can be a burden, but as we will see, most of the time the appropriate model family is obvious. For the impatient readers, here is the recipe: Answer the following three questions about the outcome variable and follow (Figure 7.1).
To make it even easier, it is practically always adequate and safe to answer Yes to the third question (over-dispersion). Based on these questions, the graph below identifies the correct distribution family and you can jump right to respective section, if you need a quick answer. In the following section (7.1)), I will provide a general explanation of why GLMs are needed and how they are constructed by choosing a response distribution (7.1.2) and a link function (7.1.1). The remainder of the chapter is organized by types of measures that are typical for design research: count data (7.2), duration measures (7.3)) and rating scales (7.4). Together with chapter 6, this introduces the family of models called Generalized Multi-level Linear Models (GMLM), which covers a huge variety of research situations. The chapter closes with a brief introduction to an even mightier class of models: GMLMs still have certain limitations. One of them is that they are all about estimating average performance. Distributional models are one further step of abstraction and they apply when the research is concerned with variance, actually (7.5).
GLM is a framework for modelling that produces a family of models (Figure 7.1). Every member of this family uses a specific link functions to establish linearity and a particular distribution, that has an adequate shape and mean-variance relationship.
Sometimes GLMs are mistaken as a way to relax assumptions of linear models, (or even called non-parametric). They are definitely not! Every member makes precise assumptions on the level of measurement and the shape of randomness. One can even argue that Poisson, Binomial and exponential regression are stricter than Gaussian, as they use only one parameter, with the consequence of a tight association between variance and mean. A few members of GLM are classic: Poisson, Binomial (aka logistic) and exponential regression have routinely been used before they were united under the hood of GLM. These and a few others are called canonical GLMs, as they possess some convenient mathematical properties, that made efficient estimation possible, back in the days of limited computing power.
For a first understanding of Generalized Linear Models, you should know that linear models are one family of Generalized Linear Models, which we call a Gaussian linear model. The three crucial assumptions of Gaussian linear models are encoded in the model formula:
The first term, we call the structural part and it represents the systematic quantitative relations we expect to find in the data. When it is a sum of products, like above, we call it linear. Linearity is a frequently under-regarded assumption of linear models and it is doomed to fail 7.1.1. The second term defines the pattern of randomness and it hosts two further assumptions: Gaussian distribution and constant error variance of the random component. The latter might not seem obvious, but is given by the fact that there is just a single value for the standard error \(\sigma\).
Linearity means that we increase the predictor by a fixed unit, the outcome will follow suit by a constant amount. In the chapter on Linear Models 4, we encountered several situations where linearity was violated.
For the learning process in the IPump study we earlier used an OFM with stairways coding to account for this non-linearity (@ref(#ofm)), but that has one disadvantage. From a practical perspective it would interesting to know, how performance improves when practice continues. What would be performance in (hypothetical) sessions 4, 5 and 10. Because the OFM just makes up one estimate for every level, there is no way to get predictions beyond the observed range.
With an LRM, the slope parameter applies to all steps, which gives us the possibility of deriving predictions beyond the observed range. To demonstrate this on the deviations from optimal path, the following code estimates a plain LRM and then injects some new (virtual) data to get extrapolations beyond the observed three tasks. Note that the virtual data comes without a response variable, as this is what the model provides (Table 7.1).
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