What is the cause for external subtitles to grow further apart from audio?

[semmel]

Hi.

Using various versions of Media Player Classic over the years, I continually run into issues where external subtitles (e.g. SRT files) will de-sync from the audio, and the gap seems to steadily grow larger.

MPC allows me to delay or speed up the subtitles, but that means I have to hit that keyboard every 10 seconds or so.

My rough estimate with this last video that did that is that I lost 1 second every 10 seconds of video.

I'd like to understand why this happens.

As far as I understand SRT files, they are text files with a timestamp that tells the video player when to show the next line of text.

So when the video player says that we have played 1 minute and 30 seconds of a video, why does that not translate in showing the subtitle with the timestamp of 1 minute and 30 seconds?

Are the subtitles routines using a different way of counting time?

Thanks!

[Subtitles]

Hi.

Using various versions of Media Player Classic over the years, I continually run into issues where external subtitles (e.g. SRT files) will de-sync from the audio, and the gap seems to steadily grow larger.

MPC allows me to delay or speed up the subtitles, but that means I have to hit that keyboard every 10 seconds or so.

My rough estimate with this last video that did that is that I lost 1 second every 10 seconds of video.

I'd like to understand why this happens.

As far as I understand SRT files, they are text files with a timestamp that tells the video player when to show the next line of text.

So when the video player says that we have played 1 minute and 30 seconds of a video, why does that not translate in showing the subtitle with the timestamp of 1 minute and 30 seconds?

Are the subtitles routines using a different way of counting time?

Thanks!

srt files are usually synched with the audio. If you run into this kind of behaviour, it might be the source is not doing a good job or the way you download the files.

[manono]

I use SRTs from time to time, also use MPC, and have never experienced that problem. Do the subs come from a different source than the video and audio, downloaded, perhaps? If so, there's a simple answer.

[lingyi]

There are two possibilities.

One is the video is a different cut from the subtitles. With added or missing scenes.

Two is the more likely, especially since the subs are drifting.

The SRT is a different frame rate than the video. There are five different possible frame rates, 30fps (NTSC), 25fps (PAL), 29.97, 23.97 (NTSC) or 24fps (film). You can change the framerate timing with https://www.videohelp.com/software/Subtitle-Workshop. The catch is determining what the original framerate of the SRT is and what framerate your video is. The latter is easy with MediaInfo. Otherwise you'll have to experiment.

[semmel]

Thanks for your replies.

These SRT files come from OpenSubtitles and were not made for the video files. I get that.

Still, I don't get why the timestamp system would be so different.

The explanation of frame rates makes the most sense to me so far, so I'll look into the tool you mentioned.

Thanks!

[davexnet]

"So when the video player says that we have played 1 minute and 30 seconds of a video, why does that not translate in showing the subtitle with the timestamp of 1 minute and 30 seconds?"

It should do, perhaps you should post here a mediainfo report of your video file, text view

[Subtitles]

Thanks for your replies.

These SRT files come from OpenSubtitles and were not made for the video files. I get that.

Still, I don't get why the timestamp system would be so different.

The explanation of frame rates makes the most sense to me so far, so I'll look into the tool you mentioned.

Thanks!

If you want perfectly synchronized subtitles timestamps with the audio (of the video), then DIY using Whisper AI speech to text software
Subtitle Edit has an integrated module so you can try that. You can find it in the Video tab menus.

[jagabo]

Still, I don't get why the timestamp system would be so different.

Movies may play at different speeds in different countries. In the USA 24 fps film is slowed to 23.976 fps. In Europe it is often sped up to 25 fps. So there is about a 4 percent difference in running time. Beyond that there are a million other reasons why subs might not match. Different regions usually have different studio and distributor logos (of different lengths) at the start. Different scenes may be cut from the original film (violence removed in Europe, sex removed in the USA). When films are broadcast on TV they often cut scenes or speed them up to make more room for ads, or to fit in a time slot. Etc.