Definition
MPEG-DASH — MPEG-DASH (Dynamic Adaptive Streaming over HTTP) is an international standard, ISO/IEC 23009-1, for streaming video over the web. It splits media into small segments described in an .mpd manifest, lets players switch quality as bandwidth changes, and works with any codec. Major video platforms use it for adaptive streaming.
How DASH works
Like HLS, DASH breaks a video into short chunks and describes them in a manifest file. The manifest, called an MPD (Media Presentation Description), is an XML document listing:
- The available video versions, each with its resolution, bitrate and codec
- The available audio versions, often in several languages or quality levels
- Subtitle tracks and timing information
The player measures the connection speed and picks the best version that will play without buffering, switching up or down every few seconds if needed.
Separate audio and video
A key feature of DASH-style delivery is that audio and video are usually stored as separate streams. A site can offer ten video qualities and three audio qualities without encoding thirty combined files. The player fetches one of each and plays them together.
DASH vs HLS
| MPEG-DASH | HLS | |
|---|---|---|
| Origin | MPEG / ISO standard (2012) | Apple (2009) |
| Manifest | .mpd (XML) | .m3u8 (text) |
| Codecs | Any | A defined list |
| Native Apple support | Limited | Yes |
Why DASH matters when downloading videos
Because audio and video come separately, a downloader has to fetch both and combine them. This step, called muxing, puts the two streams into one container such as MP4. It explains a few things you might notice:
- High-quality downloads can take a moment longer to prepare, because two streams are being joined.
- Saving audio only can be fast, since only the audio stream is needed.
- Higher resolutions sometimes exist only as video-only DASH streams, so a "video without sound" file usually means the merge step was skipped by a simpler tool.
SaveVidr's engine (yt-dlp with ffmpeg) handles this merging on our servers, so you get one playable file. DASH is also used by paid streaming services together with DRM; encrypted streams like those cannot be downloaded, and SaveVidr does not attempt to. Only download videos you are permitted to save.
FAQ
Frequently asked questions
What is an MPD file?
An MPD is the XML manifest used by MPEG-DASH that describes all available video, audio and subtitle streams and their segments.
Why did my downloaded DASH video have no sound?
The tool likely saved only the video stream; DASH audio is separate and must be merged in, which SaveVidr does automatically.