Subtitles and audio tracks: formats, how to choose them and why they sometimes don’t show

4 min read

The same video can carry several audio tracks (languages, commentary, audio description) and several subtitle tracks. Choosing them is easy; understanding why they sometimes don’t appear, not so much. Here are the most common formats, how to choose them in Whatplay and what to check when something goes wrong.

Text and image-based subtitles

There are two big families:

Text: the file stores the lines and their timings, and the player draws them. They take up very little space and can be edited with any text editor.
Image-based: each subtitle is a ready-made picture. These are the ones on Blu-ray discs (PGS) and DVDs (VobSub) and in many digital TV broadcasts (DVB). You can’t change their font or correct their text.

The most common text formats

SRT (SubRip)

The simplest and most widespread. Each subtitle has a number, a start time and an end time, and the text, with a blank line between one subtitle and the next:

1
00:00:02,500 --> 00:00:05,000
¿Has visto lo que hay en la playa?
2
00:00:05,800 --> 00:00:08,200
Ven, corre, antes de que suba la marea.

WebVTT (.vtt)

The subtitle format of the web and of HLS. It’s very similar to SRT: it starts with the line WEBVTT, the milliseconds come after a period (00:00:02.500) and it supports positioning and some styling.

ASS and SSA

Very popular with amateur subtitlers: they allow fonts, colors, exact positions and effects such as karaoke. Not all players draw these effects the same way, and the most elaborate ones may look simpler.

Others

TTML, in XML, common on streaming platforms and in DASH; and the subtitles that travel inside the video signal itself, CEA-608 and CEA-708, which Whatplay labels “CC”.

Where subtitles live

Inside the file: an MKV can carry many subtitle tracks; an MP4 usually carries fewer.
Inside the stream: in HLS and DASH, as separate tracks declared in the manifest.
In a separate file: an .srt or .vtt next to the video. For Whatplay to load it, put it in a W3U list in the video’s subtitle field, for example "subtitle": "https://example.com/videos/viaje.srt". Whatplay recognizes the format by the address’s extension (.srt, .vtt, .ass, .ssa or .ttml), so don’t change it. The W3U format is explained in M3U, M3U8 and W3U.

How to choose them in Whatplay

In the player, tap “Options”.
In “Subtitles”, choose one or “Off”. When you open a video, subtitles start off until you ask for them.
In “Audio”, choose the sound track. Each one shows its language, codec and channels (for example, “AC3 5.1”); those without a name appear as “Track 1”, “Track 2”…

If you always want the same audio language, choose it in Settings › Player › “Preferred audio language” and it’ll be selected automatically whenever the video has it. Next to some subtitles you’ll see “SDH”, made for deaf and hard-of-hearing viewers, which also describe sounds, or “forced”, which only translate what’s said or written in another language, like a sign or an odd line here and there. The help sums it up in Subtitles and audio tracks.

Why they sometimes don’t show

“This video has no subtitles”: the file or stream doesn’t include any. Some websites load subtitles with their own player, separately from the video, so they don’t come along with it.
Strange symbols appear instead of accented letters: the file isn’t in UTF-8. Open it in a text editor and save it with that encoding.
They’re early or late: the file is for another version of the video, with a different cut or frame rate. Look for one made for your version, or fix the timings with a subtitle editor.
The external file won’t load: open its address in a browser. If it doesn’t download, the player won’t be able to load it either.
The format isn’t recognized: check that the address’s extension matches what’s inside.

Audio tracks that make no sound

If a track shows up in the list but makes no sound, most likely the phone can’t decode its format, as often happens with DTS or TrueHD. Leave Settings › Player › “Playback engine” on Automatic: that way, whatever the system can’t open, Whatplay’s FFmpeg will. We explain it in video and audio formats. If a movie has the track in your language in a demanding format and another one in AAC, the AAC track will cause fewer problems on any device.

When casting to the TV

When you cast to a Chromecast, text subtitles can reach the TV through your phone; in “Options” › “TV” you’ll see whether they’re being sent. On Android 17 or later they need the “Nearby devices” permission, and Whatplay lets you know if it’s missing. Image-based subtitles aren’t sent to the TV. And while the TV is playing, you can only change the subtitles in “Options”: choose the audio track before you cast.