Batch convert subtitle files

Batch converting subtitle files typically means transforming multiple subtitle files (like .srt, .ass, .sub, etc.) from one format to another or adjusting their encoding, timing, or style all at once instead of doing it one by one.

Here’s a detailed guide and explanation on how to batch convert subtitle files, including tools and methods you can use:

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Understanding Subtitle Files and Why Batch Conversion is Needed

Subtitle files come in many formats:

• SRT (SubRip Text): The most common plain text subtitle format.

• ASS (Advanced SubStation Alpha): Supports styling, positioning, and effects.

• SUB: Binary or text-based subtitle files used in DVD and Blu-ray.

• VTT (WebVTT): For web video subtitles.

• Others like SSA, IDX, etc.

Batch conversion is useful if you:

• Need to convert a folder of subtitles to a consistent format (e.g., all to SRT).

• Want to fix encoding issues (e.g., convert from ANSI to UTF-8).

• Need to shift subtitle timings uniformly (delay or advance).

• Want to strip styling from ASS to plain SRT.

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Tools for Batch Subtitle Conversion

1. Subtitle Edit (Windows)

• Free, open-source subtitle editor.

• Supports batch conversion of many subtitle formats.

• Can convert a folder full of subtitles in one go.

How to batch convert:

• Open Subtitle Edit.

• Go to File > Batch convert.

• Add the subtitle files or folder.

• Choose the target format (e.g., SRT).

• Set encoding and other options.

• Start conversion.

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2. ffmpeg (Cross-platform, command line)

• Powerful multimedia tool, can convert subtitle streams.

• Useful to extract subtitles or convert formats embedded in videos.

• For subtitle files, you may need scripts to batch process multiple files.

Example command to convert one .ass to .srt:

bash
CopyEdit
ffmpeg -i input.ass output.srt

For batch, a shell script or batch file can loop over files.

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3. Python + Subtitle Libraries

• Use Python packages like pysubs2 or subtitleconverter.

• Write scripts to batch process folders of subtitles.

• Allows custom logic (e.g., timing shifts, encoding fixes).

Example snippet (using pysubs2):

python
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import pysubs2
import os

input_folder = "subs_in"
output_folder = "subs_out"

for filename in os.listdir(input_folder):
    if filename.endswith(".ass"):
        subs = pysubs2.load(os.path.join(input_folder, filename))
        outname = filename.replace(".ass", ".srt")
        subs.save(os.path.join(output_folder, outname))

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4. Online Converters

• Websites offering batch upload and conversion.

• Limited by file size, privacy, and speed.

• Useful for small batches or single conversions.

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Batch Conversion Steps Summarized

1. Gather all subtitle files into a folder.

2. Choose your target format and conversion tool.

3. Set conversion parameters:

   • Output format (SRT, ASS, etc.)

   • Encoding (UTF-8 recommended)

   • Timing adjustments (if needed)

4. Run batch conversion with chosen tool or script.

5. Verify converted files for correctness and sync.

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Tips for Batch Subtitle Conversion

• Always back up your original subtitles.

• Check for format-specific quirks; some styles or metadata may be lost when converting.

• Use UTF-8 encoding to avoid character corruption.

• For timing shifts, use tools with built-in time adjustment features.

• Validate subtitle files after conversion in a media player or subtitle editor.

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If you want, I can help create a detailed step-by-step guide for a specific tool or a script to batch convert your subtitle files. Just let me know your platform (Windows, Mac, Linux) and preferred subtitle formats.