Subtitles appear twice sometimes

[helloyanis]

Checklist

• I am able to reproduce the bug with the latest version given here: CLICK THIS LINK.
• I made sure that there are no existing issues - open or closed - which I could contribute my information to.
• I have read the FAQ and my problem isn't listed.
• I have taken the time to fill in all the required details. I understand that the bug report will be dismissed otherwise.
• This issue contains only one bug.
• I have read and understood the contribution guidelines.

Affected version

0.27.0

Steps to reproduce the bug

1. Open a video with colored subtitles such as this one
2. Turn on subtitles for "English (United Kingdom)"

Expected behavior

The subtitles display correctly, like on the official youtube app as shown below

Actual behavior

The subtitles' color and tempo is correct, but they appear twice, as shown below

Screenshots/Screen recordings

Screen_Recording_20240623_083520_NewPipe.mp4

Logs

No response

Affected Android/Custom ROM version

Android 14 / Stock rom

Affected device model

Samsung Galaxy A52s 5G

Additional information

No response

[opusforlife2]

Hmmm. This is occurring on Piped and Invidious too.

[haoyeau]

After debugging on this case, we found out that the decoded subtitle input stream indeed contain duplicate subtitle text. Therefore, this should be a subtitle extractor issue. And the player is totally good for rendering subtitle.

[helloyanis]

After debugging on this case, we found out that the decoded subtitle input stream indeed contain duplicate subtitle text. Therefore, this should be a subtitle extractor issue. And the player is totally good for rendering subtitle.

So should I open the issue elsewhere instead?

[haoyeau]

Sorry, I do not know it either.
I traced back the stream info to get the subtitle
As you can see clearly from this, the subtitle itself is duplicated.

[Thompson3142]

This is already open as an issue on the extractor side: TeamNewPipe/NewPipeExtractor#1102 . Not sure if this issue should be closed since it also needs work on the NewPipe side to function after the extractor changes @opusforlife2 .

[helloyanis]

This is already open as an issue on the extractor side: TeamNewPipe/NewPipeExtractor#1102 . Not sure if this issue should be closed since it also needs work on the NewPipe side to function after the extractor changes @opusforlife2 .

I think I'll keep it open here until it's fixed in NewPipe. Even if it depends on something else it's still an issue that occurs in the app. I'll close it once the extractor is updated and is fixed in newpipe.

[opusforlife2]

Normally, an issue that also needs changes in the extractor is labelled as such and left open. In this case, the extractor itself contains the bug, so NPE users like Piped are also affected. I do not know whether there need to be changes made to the app as well after the extractor is fixed, so I'd keep this open to be safe.

[TransZAllen]

Hi,

I think this issue should be fixed, and here are three practical reasons:

1. Poor user experience — looks strange
   Duplicate subtitle lines (same text shown twice at the same begin/end time) feel confusing and unnatural to users.

2. Not the subtitle author’s intention
   The duplicated <p> segments are usually an artifact of YouTube’s TTML output (for multi-track compatibility or internal formatting reasons).
   Even though the duplication exists in the raw TTML, it is not meant to be shown visually — YouTube’s own player does not display them.
   We can detect repeated TTML segments with identical timestamps and text, and remove them to better reflect the author’s intended subtitle content.

3. Affects both playback and downloaded files
   NewPipe uses the raw TTML in two places: on-screen subtitle rendering and downloaded .srt files.
   As a result, users see the duplicate lines while watching videos and get duplicated entries in downloaded subtitles.
   Here is a snippet of the downloaded *.srt subtitle file with the latest dev branch of NewPipe (Commits on Nov 2, 2025) (from the YouTube video link: https://www.youtube.com/watch?v=b7vmW_5HSpE):

   1
   00:00:01,352 --> 00:00:01,852
    Land mines 
    I've left them everywhere 
   
   2
   00:00:01,352 --> 00:00:01,852
    Land mines 
    I've left them everywhere 

   And the snippet of its corresponding raw TTML subtitle:

   <p begin="00:00:01.352" end="00:00:01.852" style="s2">
   <span style="s3">​</span>
   ​
   <span style="s4">​ ​Land </span>
   <span style="s5">mines​ ​</span>
   <span style="s3">
   ​
   <br/>
   ​
   </span>
   <span style="s5">​ ​I've left them everywhere​ ​</span>
   <span style="s3">​</span>
   </p>
   <p begin="00:00:01.352" end="00:00:01.852" style="s2">
   <span style="s3">​</span>
   ​
   <span style="s4">​ ​Land </span>
   <span style="s5">mines​ ​</span>
   <span style="s3">
   ​
   <br/>
   ​
   </span>
   <span style="s5">​ ​I've left them everywhere​ ​</span>
   <span style="s3">​</span>
   </p>

Conclusion: This is a real, user-facing bug (or omission), and addressing it would improve NewPipe’s subtitle experience.

[TransZAllen]

1. Where duplicates come from (visual data flow)

Duplicates don't originate from the author — they appear during YouTube's server-side conversion. Simple flow:

flowchart TD
    A["Author Upload subtitle<br/>*.SRT / VTT / SBV / TTML<br/>(refer to https://support.google.com/youtube/answer/2734698?hl=en)"] 
      -->|Convert to YTT/TTML| B["YouTube Server<br/>Processing<br/>(Add redundant &lt;p&gt;. For compatibility??)"]

    B -->|Remote TTML URL| Merge[ ]
    Merge --> C["NewPipe App<br/>Fetch URL"]
    Merge --> F["Official YouTube Player<br/>(Web / App)"]

    C --> D["ExoPlayer Rendering<br/>Raw TTML → Duplicate / thick text"]
    C --> E["Manual Download → .srt<br/>Also contains duplicates"]

    F --> G["Hidden auto-merge&dedup<br/>→ Clean single line<br/>(only for screen-display, not for original TTML subtitles)"]

    style A fill:#e1f5fe
    style B fill:#fff3e0
    style C fill:#f3e5f5
    style D fill:#ffebee
    style E fill:#ffebee
    style F fill:#e8f5e8
    style G fill:#e8f5e8
    style Merge fill:none,stroke:none

Loading

Key point:

• Although YouTube accepts SRT/VTT/SBV/TTML uploads, all formats are internally converted into YouTube’s own TTML/YTT representation.
• During this conversion, YouTube frequently produces redundant <p> elements, but YouTube provides no official documentation explaining why they are generated.
• [user-facing] YouTube’s official player merges/filters (dedup) these redundant segments at render time. (Note: The remote TTML file always contains the original (possibly duplicated) <p> segments.)
• [user-facing] NewPipe receives the raw TTML and shows all <p> elements as-is → producing visible duplicates both on-screen and in exported .srt files.

[TransZAllen]

2. YouTube Official docs / explanation

There is no clear public documentation from YouTube describing this exact conversion/duplication behavior. Google mentions TTML/partial support in general (e.g. supported formats), but not this specific artifact:

• See: YouTube Help(https://support.google.com/youtube/answer/2734698?hl=en) — Supported captions & subtitles formats.
  (There is no changelog or official note addressing raw duplicate <p> entries, so this appears to be a server-side, black-box artifact.)