What Happens to Subtitles After EncoX Converts a Video: Text, ASS and PGS
Subtitles do not all get the same treatment when EncoX converts a video. Text-based tracks such as SRT and ASS are carried into the resulting MP4 as embedded subtitles. ASS styling such as positioning and color is reduced to plain text, while Blu-ray image subtitles (PGS) are scanned and recognised as text, so they come back as a subtitle track you can resize and restyle — recognition can make mistakes.
This article is only about subtitles already inside the video file. EncoX does not import an external subtitle file, create subtitles, translate them, or export a separate subtitle file afterward. If subtitles are essential to the way you watch a video, especially if you rely on PGS or on ASS layout, it is worth checking the subtitle type before you convert.
1. After conversion, subtitles have two very different outcomes
The useful distinction is not whether the video file is called MKV, MP4, AVI or TS. What matters here is whether the subtitle track contains text or images. Text can be converted into a subtitle form that fits inside the resulting MP4. Image subtitles cannot go in as they are, so EncoX reads them first, and the outcome is a text track.
EncoX keeps the content of text subtitles, simplifies ASS styling, and turns PGS image subtitles into a text track by reading them.
Subtitle handling is one part of a conversion. It does not by itself tell you whether the video stream will be left as-is or fully converted. That separate decision is explained in how EncoX decides which conversion path to use.
2. Text subtitles stay with the video as embedded MP4 subtitles
SRT and ASS are text-based subtitle formats. Their core data is written text tied to timing information. SSA, WebVTT and other text formats have no device sample behind them yet, so this page does not present them as verified. When those tracks are already inside the source video, EncoX converts them into embedded subtitles that can live inside the output MP4.
“Preserved” does not mean the original subtitle format is copied over byte for byte. It means the subtitle content remains available inside the converted video. EncoX does not also create a separate SRT, ASS or other subtitle file alongside the MP4.
This is why an MKV that contains subtitles should not be expected to produce an MP4 whose subtitle tracks are identical in every detail. The container changes, so the subtitle representation has to fit the destination as well. If your separate question is whether the video picture itself needs to be recompressed during MKV-to-MP4 conversion, see when EncoX can convert MKV to MP4 without recompressing the video.
3. ASS keeps the words, not the original layout
ASS is the text format most likely to surprise people because it can carry much more than dialogue and timing. An ASS track may also use positioning, colors and other layout choices. EncoX keeps the subtitle text, but those presentation details do not survive the conversion. The result is plain text.
For ordinary dialogue, that may still deliver the information you need. The difference becomes much more visible when layout is part of the meaning: lyrics placed in a particular region of the frame, different colors used for different speakers, or bilingual subtitles arranged in separate positions.
With ASS, the important boundary is simple: the words remain, while positioning, color and related layout styling do not.
If you mainly need readable dialogue, that tradeoff may be acceptable. If the layout itself carries meaning, checking the ASS track before conversion is one of the most important subtitle checks you can make.
4. PGS image subtitles are read and rewritten as text
PGS is fundamentally different from SRT or ASS. It is an image subtitle track: what appears on screen is stored as subtitle graphics rather than ordinary text that can simply be written into an MP4 subtitle track. So EncoX takes another route - it scans the whole track, reads the dialogue as text and produces a text subtitle track. This recognition line has been verified on a real device only for the Blu-ray PGS family; no promise is made here about other image subtitle formats. If a track yields no readable text, or the line cannot open it at all, that subtitle track is simply absent from the output: the video still converts, and nothing extra is reported to you.
Because MP4 embedded subtitles cannot hold those images, EncoX takes another route: the track is scanned, the lines shown in the pictures are recognised as text, and a text subtitle track is written into the result. Recognition makes mistakes — individual words, speaker attribution and distinctions that relied on layout can come out wrong — so the track deserves a pass of your own. There is no switch for this step: when a source carries PGS, that track is read.
If a video depends on PGS image subtitles, what you get back is a track of recognised text you can resize and restyle, not the original subtitle graphics.
Real-device runs cover the PGS family only, and this page makes no promise about other image subtitle formats; what stays narrow is the recognition-mistake boundary and the fact that a track yielding nothing simply is not in the file. If subtitles are non-negotiable for a particular movie or episode, the subtitle type deserves the same attention as the picture and audio.
5. External subtitle files cannot be added during conversion
If you have a video file plus a separate SRT or ASS file, EncoX cannot import that external subtitle file and merge it into the video during conversion. EncoX only processes subtitle tracks that are already embedded in the source video.
That makes one wording distinction important: EncoX can process SRT or ASS when that subtitle is inside the video file. It does not mean EncoX offers an “add subtitle file” step where you can browse for an external SRT and attach it to the conversion.
The reverse workflow is also outside the scope of the app. After conversion, EncoX does not extract an embedded subtitle track into a standalone subtitle file. Its job is to convert the video into an MP4 that is easier to open directly on iPhone, iPad and Mac, not to act as a subtitle import, extraction or management tool.
6. Multiple subtitle tracks are processed one by one, but the Simplified/Traditional distinction is lost
A video can contain more than one subtitle track, and EncoX processes those tracks individually rather than stopping after the first one. For example, if a file contains 3 text subtitle tracks, each is handled in turn. If the track list mixes text and image subtitles, the text tracks follow the text-subtitle rules while image subtitle tracks go through recognition.
Chinese subtitles have one additional limitation: the Simplified-versus-Traditional distinction is lost during conversion. The subtitle text remains subject to the normal text-subtitle handling, but the converted file no longer distinguishes Simplified from Traditional Chinese. That may not matter if you only read the subtitle itself, but it matters if you need those two Chinese variants to remain clearly differentiated after conversion.
7. Why “subtitles are preserved” is too vague to be useful
Calling all of these tracks “subtitles” is convenient, but it hides the exact difference that determines the result. Text subtitles contain words and timing. Image subtitles contain pictures. EncoX can convert the former into MP4 embedded subtitles; the latter cannot go into that kind of track as it is, so the pictures are read and written out as text.
ASS sits in the middle. It is still text-based, so the words can remain, but some of the richer layout information has nowhere to go in the resulting subtitle form. The conversion therefore keeps the essential text while dropping positioning and color styling.
The practical takeaway is that the presence of a subtitle track is not enough information on its own. If subtitles are only a reading aid, text-track handling may be all you need. If the subtitle graphics or layout are part of the presentation, you should treat that as a conversion boundary rather than assume “subtitle support” covers it.
8. Limits: what this workflow cannot do
- If you rely on PGS image subtitles, what you get is recognised text rather than the original graphics, and recognition can be wrong; this path has been verified on a real device only for PGS, and no promise is made here about other image subtitle formats.
- If you want to add an external SRT, ASS or other subtitle file during conversion, EncoX does not support that import workflow.
- If you depend on ASS positioning or color to understand lyrics, speakers or bilingual layout, those styling details will become plain text.
- If you need a separate subtitle file after conversion, EncoX does not export one.
- If you need Simplified and Traditional Chinese subtitles to remain explicitly distinguished after conversion, that distinction is not retained.
- If you wonder which subtitle track ends up first: subtitle tracks carry no default flag, so the order in the output is the order in the source.
Common questions
Will my subtitles still be there after I convert the video?
It depends on the subtitle type. SRT and ASS text subtitles are converted into embedded MP4 subtitles. ASS styling is simplified. PGS image subtitles are read and rewritten as a text track.
My subtitles are PGS. What happens after conversion?
They come back as text. PGS is an image subtitle type, so EncoX scans the pictures and writes out the lines it recognises; some of those words can be wrong, and the original graphics and their layout do not come along.
Will ASS colors and positioning survive?
No. The text content remains, but positioning, color and related ASS layout styling are reduced to plain text. If the layout carries meaning, the converted result can look substantially different.
Can I choose my own SRT file and add it?
No. EncoX does not import external subtitle files. It only processes subtitle tracks already embedded in the source video.
If a video has several subtitle tracks, does EncoX keep only one?
No. EncoX processes subtitle tracks one by one. Text tracks follow the text-subtitle rules; image subtitle tracks among them go through recognition.
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