Adding subtitles

[kirkmc]

Can you add (or embed) an srt file into it's video file?
For example you have an .mp4 and .srt file on a stick to plug into the TV. It plays the video but ignores the subs.

[ProWo]

You have to mux the video and the srt with g.e. mkvtoolnix.
Set the sub as forced.

[jagabo]

The MP4 container doesn't really support SRT. The subs have to be converted to a format that's acceptable for MP4. You can mux SRT subs into an MKV file.

But beware, lots of TVs (and some standalone media players) don't support subs that are muxed into an MP4 or MKV container. The SRT has to be in a separate file with the same base name as the video. For example "My Video.MKV" and "My Video.SRT".

[kirkmc]

I found muxing is the process of merging streams of video with audio or closed captions. In many cases, this involves downgrading your resolution and quality. I've downloaded mkvtoolnix but where can I find instructions for how to add the subs ? How much downgrading occurs ?
jagobo, I often need to make sure .srt and video use the same name but you're saying this is still needed after "muxing" ? So the result is still 2 files ?

[abolibibelot]

@jagabo

The MP4 container doesn't really support SRT. The subs have to be converted to a format that's acceptable for MP4.

I have a few MP4 files which I happen to have found on dark corners of teh Internetz which do have embedded SRT subtitles. How is that possible ?
And then what would be a format acceptable for MP4 ?

But beware, lots of TVs (and some standalone media players) don't support subs that are muxed into an MP4 or MKV container. The SRT has to be in a separate file with the same base name as the video. For example "My Video.MKV" and "My Video.SRT".

Indeed, if that doesn't work, it's unlikely to work better with muxed subtitles. In which case, if the standalone device can't be updated or replaced, the only solution is to “burn” the subtitles so that they become part of the video track. (Means re-encoding the whole file, with some quality loss, depending on the chosen bitrate / quality settings.)

@kirkmc

I found muxing is the process of merging streams of video with audio or closed captions. In many cases, this involves downgrading your resolution and quality. I've downloaded mkvtoolnix but where can I find instructions for how to add the subs ? How much downgrading occurs ?

Strictly speaking, muxing means associating two or more streams (video stream, audio streams, subtitles stream...) into a single file, it's a very quick process and doesn't degrade the quality whatsoever. Re-encoding on the other hand means creating a new file with new streams generated by the respective encoder, and some quality loss necessarily occurs. How much, again, depends on the quality settings, for instance using x264 with a “CRF” = constant rate factor of 20 or below usually yields a very good quality, barely distinguishable from the input, but using a “CRF” value of 25 or more yields a significant quality loss (even if the resulting file can be larger than the original, if the original has a lot of noise and/or movement).

As for using mkvtoolnix, it's pretty straightforwrd, you drag-and-drop the video file, the SRT file, choose the name and location of the output, then click on “Start multiplexing”. There are many options for more advanced operations, but this should be all you neeed for that simple task.

jagobo, I often need to make sure .srt and video use the same name but you're saying this is still needed after "muxing" ? So the result is still 2 files ?

No, it's two different things. If the device you want to play the file with does recognize subtitles simply embedded (muxed) into a MKV file, then do that. If it doesn't, then try putting the video file and a separate SRT file, with the same name (minus the extension), in the same folder. If that doesn't work either, then the only option is to “burn” the subtitles into the video, so that anything that can play the video will always display the subtitles — which degrades the quality somewhat. And that can't be done with mkvtoolnix (it does not re-encode), another software must be used, like Handbrake or MeGUI or ffmpeg among many others.

[jagabo]

I found muxing is the process of merging streams of video with audio or closed captions. In many cases, this involves downgrading your resolution and quality. I've downloaded mkvtoolnix but where can I find instructions for how to add the subs ? How much downgrading occurs ?

By definition muxing (multiplexing) cannot degrade the quality. It's simply taking whatever is in the source file and putting it in a new file -- there is no reencoding. What degrades the quality is hard subbing. Decompressing the source video, writing subtitles onto the frames, then reencoding the video.

jagobo, I often need to make sure .srt and video use the same name but you're saying this is still needed after "muxing" ? So the result is still 2 files ?

No. I'm saying your TV probably can't display subs muxed into the same file as the audio and video. You have to leave them as a separate file.

[kirkmc]

Thank muchly for the nice replies. I understand better and have a try.

[jagabo]

@jagabo

The MP4 container doesn't really support SRT. The subs have to be converted to a format that's acceptable for MP4.

I have a few MP4 files which I happen to have found on dark corners of teh Internetz which do have embedded SRT subtitles. How is that possible ?
And then what would be a format acceptable for MP4 ?

MP4 supports WEBVTT subtitles. I didn't realize how close that is to SRT. The major differences are: the first line must be "WEBVTT", only UTF8 is supported, and a cascading style sheet is used for fonts rather than the Font keyword.

http://www.kaizou.org/2013/03/subtitles-and-chaptering-using-text-tracks.html

[ProWo]

If you want mp4 as container you can use my clever Ffmpeg-GUI for multiplexing your video and srt subtitle into a mp4 container. The srt will be converted into the compatible format automatically.

[kirkmc]

What's a 7z file ? DO I need something special to open/run ?

[kirkmc]

>As for using mkvtoolnix, it's pretty straightforwrd, you drag-and-drop the video file, the SRT file, choose the name and location of the output, then click on “Start multiplexing”.
I was able to drag the mp4 file into the source file window, but doing this to the .srt file brought up a pile of options. I think the right one is Add as new source files to the current multiplex settings. Correct ?

[abolibibelot]

What's a 7z file ? DO I need something special to open/run ?

Well, we all have to start somewhere... but at some point you have to start. Answering that question would be like letting a 12 years old boy keep on riding his bicycle with those little wheels behind.
(Right now I'm translating a scene of a movie called Nagasaki 1945 – Angelus no Kane, where a character who was badly burned following the nuclear blast is urged by the young doctor — whose ensuing books the movie is based on — to crawl from his bed to a stretcher, so that he can be transported to the basement, as a huge storm is hitting the upper floors, since it's too painful if someone helps him... to put things in perspective.)

I was able to drag the mp4 file into the source file window, but doing this to the .srt file brought up a pile of options. I think the right one is Add as new source files to the current multiplex settings. Correct ?

Correct. (I'll admit that this menu is quite confusing, especially for subtitles, which can't be “appended” alone, and I'm not sure what the “new multiplex settings” options do.)