Free online SRT to AAC converter

When a player or device needs spoken audio instead of subtitle captions, an SRT file must be rendered as speech and saved as AAC. This creates a narrated audio track; it is not a direct audio-format transcode.

What the SRT format is

SRT is a plain-text subtitle format containing numbered captions, start and end times, and the words to display. Video editors, media players, and subtitle tools such as Subtitle Edit create or edit SRT files; they commonly accompany downloaded videos or recordings.

What the AAC format is

AAC is a lossy audio codec used in formats such as M4A and in raw AAC files. It provides good audio quality at relatively low bitrates and is supported by most phones, computers, and media players. Converting subtitles to AAC means using text-to-speech (TTS) to generate speech, not preserving the subtitle text as captions.

How to convert SRT to AAC

Online on 101convert.com

1. Open the SRT-to-AAC converter page and upload the subtitle file. Multiple files can be added as a batch; the page shows the per-file size limit.
2. Before converting, set the voice language, reading speed, and subtitle timing as needed.
3. Start the conversion, then download the resulting AAC audio.

Offline with desktop software

For local processing, Python with the free pyttsx3 TTS library can synthesize speech using installed system voices. It runs on Windows, macOS, and Linux; the available voices depend on the operating system. Install Python packages with python -m pip install srt pyttsx3 pydub, and install FFmpeg separately.

Save this script beside the subtitle file as make_audio.py. It creates a WAV mix, placing each spoken cue at its SRT start time:

from pathlib import Path
import srt
import pyttsx3
from pydub import AudioSegment

subs = list(srt.parse(Path("captions.srt").read_text(encoding="utf-8-sig")))
engine = pyttsx3.init()
clips = []

for i, sub in enumerate(subs):
    text = " ".join(sub.content.split())
    if not text:
        continue
    filename = f"cue_{i}.wav"
    engine.save_to_file(text, filename)
    engine.runAndWait()
    clips.append((int(sub.start.total_seconds() * 1000), AudioSegment.from_wav(filename)))

total_ms = max((int(sub.end.total_seconds() * 1000) for sub in subs), default=0)
mix = AudioSegment.silent(duration=total_ms)
for start, clip in clips:
    if start + len(clip) > len(mix):
        mix += AudioSegment.silent(duration=start + len(clip) - len(mix))
    mix = mix.overlay(clip, position=start)
mix.export("narration.wav", format="wav")

Run python make_audio.py, then encode the result as an AAC file with ffmpeg -i narration.wav -c:a aac -b:a 128k -f adts narration.aac. The script leaves temporary cue WAV files in the working folder.

Quality and compatibility

SRT contains no recorded voice, so the selected TTS voice determines pronunciation, accent, and vocal quality. Speech can run past a subtitle’s end time; the script preserves cue start times and overlaps audio if cues overlap, but does not shorten speech to fit each cue. A 128 kbit/s AAC setting is a practical starting point for spoken narration; use a higher bitrate if the output also contains music or other detailed audio.