# Save raw TTML with open("captions.ttml", "wb") as f: f.write(resp.content)
This ignores styling and positioning. For roll-up captions (multiple lines changing within the same time range), you’ll need a more complex merging logic. 6. Common Pitfalls & How to Fix Them 6.1 Overlapping Timings TTML allows overlapping <p> elements (multiple simultaneous captions). SRT does not. FFmpeg usually merges them with \n , but sometimes you lose data. Fix: Use ffmpeg -i input.ttml -c:s mov_text output.mp4 to keep overlapping captions in a compatible container. 6.2 Embedded Fonts / Images Some TTML files reference external fonts or PNG sprites. When you download the TTML alone, those assets are missing. Fix: Download the full HLS segment or use wget -r on the caption asset directory. 6.3 ttp:timeBase="media" with No Framerate Example: <p begin="1000t" end="2000t"/> Fix: Find the media framerate (often 30fps) from the video manifest. Then time_seconds = ticks / framerate . 7. Legal & Ethical Notes Downloading TTML files may violate a platform’s Terms of Service if you bypass DRM or redistribute content. However, downloading your own content (e.g., from an LMS where you’re the instructor) or using TTML for accessibility research is generally acceptable. ttml download
# Parse and convert to SRT manually root = etree.fromstring(resp.content) ns = {"tt": "http://www.w3.org/ns/ttml"} cues = [] # Save raw TTML with open("captions
import glob from lxml import etree combined = etree.Element("tt", nsmap={None: "http://www.w3.org/ns/ttml"}) body = etree.SubElement(combined, "body") div = etree.SubElement(body, "div") Common Pitfalls & How to Fix Them 6