Tweaking Movie Subtitles with R

April 10, 2013

(This article was first published on theBioBucket*, and kindly contributed to R-bloggers)

I use R to fix subtitles that are not in sync with my movies. For the example below the subs were showing too early – so I added some time to each sequence in the srt file. For simplicity I used exactly 1 second in the below example.
You’ll see that I use my function dl_from_dropbox(), on which I wrote a post previously, to get the example file!

options(digits = 12)
options(digits.secs = 3)

### get subtitle example file:
dl_from_dropbox <- function(x, key) {
bin <- getBinaryURL(paste0("", key, "/", x),
ssl.verifypeer = FALSE)
con <- file(x, open = "wb")
writeBin(bin, con)
message(noquote(paste(x, "read into", getwd())))

dl_from_dropbox("", "wojo9k8v8cezs9g")
shell.exec("") #I use the MS text-editor to view srt files


### tweak the file by changing the time - i.e., I add 1 sec to all sequences here:
t <- readLines("")
tt <- unlist(strsplit(t, " --> ")) #split time start/end

x <- grep("\\d{2}:\\d{2}:\\d{2},\\d{3}", t) #ids of time data in t
y <- sort(c(x, x+1)) #ids of time data in tt

ttt <- gsub(",",".", tt[y]) #replace decimal comma

(a <- strptime(ttt, format="%H:%M:%OS", tz="GMT")) #convert to date/time
(b <- as.numeric(a)) #convert to number

c <- 1 #add 1 sec

(d <- as.POSIXct(as.numeric(b+c+1e-6), origin="1970-01-01", tz="GMT")) #convert back
(e <- format(d, "%H:%M:%OS")) #re-format
(f <- gsub("\\.", ",", e)) #replace decimal point

id_t1 <- seq(1, length(y), 2)
id_t2 <- seq(0, length(y), 2)

(g <- paste0(f[id_t1], " --> ", f[id_t2])) #bring into original form

t_new <- t
t_new[x] <- g #insert new sequences into original data

### save to new file:
write(t_new, "")
shell.exec("") #I use the MS text-editor to view srt files

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