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Glossary

DASH Streaming

Also known as: MPEG-DASH, Dynamic Adaptive Streaming over HTTP

In a DASH stream, the server publishes a small XML file called a manifest (usually with a .mpd extension) that lists all the available video qualities (e.g. 360p, 720p, 1080p) and audio tracks. The player downloads the manifest first, picks the highest video quality your bandwidth supports, and then fetches small chunks of that quality as you watch. If your connection slows down, the player automatically switches to a lower quality without interrupting playback.

The key consequence for downloading: in a DASH stream, video and audio are stored as separate files. A simple downloader that grabs only the video chunks ends up with a silent file. This is why Reddit videos so often download without audio — most general-purpose tools only fetch the video stream and skip the parallel audio stream entirely.

Fixing this requires merging the streams server-side using FFmpeg, which is what DropZap does for every Reddit, Twitter, and Facebook video. The result is a single MP4 file with both video and audio, ready to play in any video player.

Try it for yourself
Download Reddit videos with audio

Related terms

M3U8
An M3U8 file is a UTF-8 encoded playlist that describes the segments of an HLS (HTTP Live Streaming) video stream. It does not contain video data itself — it lists the URLs of small .ts (Transport Stream) chunks that, when played in order, produce the full video.
FFmpeg
FFmpeg is an open-source command-line library for handling video and audio: it can convert between formats, extract audio, merge video and audio streams, transcode codecs, trim clips, and much more. It is the underlying engine inside almost every video tool on the internet, including online converters and downloaders.
MP4
MP4 (MPEG-4 Part 14) is a digital container format that holds video, audio, subtitles, and metadata in a single file. It is the dominant video format on the modern internet — TikTok, Instagram, YouTube, X / Twitter, Facebook, and Reddit all serve videos as MP4 internally.
Bitrate
Bitrate is the amount of data used to encode each second of video, measured in kilobits per second (kbps) or megabits per second (Mbps). Higher bitrate means more data per second, which means better visual quality but larger file size. At the same resolution, a higher-bitrate video looks substantially better than a lower-bitrate one.