Using shiny and plotly, how can I animate a vertical line on a time series that scrolls with the current frame of an embedded movie?

I am making a dashboard using R, shiny and plotly. I would like to show a video, and beneath it a plot of a time series that relates to each moment in the video. When the user plays the video, I want to show a vertical line on the plot that corresponds to current playing time on the video. In other words, it's a sort of scrolling playhead.

The code and toy data here achieves what I want, but poorly. There are two problems.

1. The line only updates about once a second. Ideally, I'd like it to move more smoothly, something like 30 frames per second to match the video.

2. As I understand plotly and shiny (ie not very well), then each time I am moving the vertical line, I am re-drawing the whole plot. With the toy data here, that may not be problem. But eventually I will be using very large data sets and doing some smoothing, so I only want to draw the time series once, and update the vertical line position by itself. There are instructions about using plotlyProxyInvoke herebut I can't implement those ideas in my case.

I'm fairly competent in R and ggplot, but this is my first time with both shiny and plotly, so apologies if I'd missing something basic. Any suggestions very much appreciated!

library(shiny)
library(video)

data <- data.frame(t=1:45,y=sample(x=50,size = 45))

ui <- fluidPage(
    mainPanel(
      video(
        "https://vjs.zencdn.net/v/oceans.mp4",
        elementId = "video"),
      tags$p( "Duration:",
        textOutput("video_seek", container = tags$strong, inline = TRUE), "/",
        textOutput("video_duration", container = tags$strong, inline = TRUE) ),
       plotlyOutput(outputId = "sparkline")
  ) )

server <- function(input, output,session) {
  output$sparkline <- renderPlotly({
    p <- ggplotly( ggplot(data,aes(x=t,y=y))+geom_line() )
    add_segments(p,x=input$video_seek,xend=input$video_seek,y=0,yend=50,inherit = F)  })
  output$video_duration <- renderText({input$video_duration })
  output$video_seek <- renderText({ input$video_seek })
}

shinyApp(ui,server)

You can use plotlyProxy together with plotlyProxyInvoke.

Idea is that you make the basic plot in the renderPlotly function and use plotlyProxyInvoke to update the trace corresponding to the sparkline.

library(shiny)
library(video)
library(plotly)

data <- data.frame(t = 1:45,
                   y = sample(50, size = 45))

server <- function(input, output,session) {
   output$sparkline <- renderPlotly({
      plot_ly(
         data,
         x = ~t,
         y = ~y,
         type = "scatter",
         mode = "lines"
      ) %>% 
         add_segments(x = 0, xend = 0, y = 0, yend = 50) %>%
         layout(xaxis = list(range = c(0, ceiling(req(input$video_duration)))))
   })
   
   output$video_duration <- renderText(input$video_duration)
   output$video_seek <- renderText(input$video_seek)
   
   observeEvent(input$video_seek, {
      plotlyProxy("sparkline") %>%
         plotlyProxyInvoke("restyle",
                           list(x = list(rep(input$video_seek, 2))),
                           1)

   })
}