Matroska Streaming

In Matroska, there are two kinds of streaming: file access and livestreaming.

File Access

File access can simply be reading a file located on your computer, but it also includes accessing a file from an HTTP (web) server or Common Internet File System (CIFS) (Windows share) server. These protocols are usually safe from reading errors, and seeking in the stream is possible. However, when a file is stored far away or on a slow server, seeking can be an expensive operation and should be avoided. When followed, the guidelines in (#implementation-recommendations) help reduce the number of seeking operations for regular playback and also have the playback start quickly without needing to read lot of data first (like a Cues element, Attachments element, or SeekHead element).

Matroska, having a small overhead, is well suited for storing music/videos on file servers without a big impact on the bandwidth used. Matroska does not require the index to be loaded before playing, which allows playback to start very quickly. The index can be loaded only when seeking is requested the first time.

Livestreaming

Livestreaming is the equivalent of television broadcasting on the Internet. There are two families of servers for livestreaming: RTP / Real-Time Streaming Protocol (RTSP) and HTTP. Matroska is not meant to be used over RTP. RTP already has timing and channel mechanisms that would be wasted if doubled in Matroska. Additionally, having the same information at the RTP and Matroska level would be a source of confusion if they do not match. Livestreaming of Matroska over file-like protocols like HTTP, QUIC, etc., is possible.

A live Matroska stream is different from a file because it usually has no known end (only ending when the client disconnects). For this, all bits of the “size” portion of the Segment element MUST be set to

1. Another option is to concatenate Segment elements with known sizes, one after the other. This solution allows a change of codec/resolution between each segment. For example, this allows for a switch between 4:3 and 16:9 in a television program.

When Segment elements are continuous, certain elements (like SeekHead, Cues, Chapters, and Attachments) MUST NOT be used.

It is possible for a Matroska Player to detect that a stream is not seekable. If the stream has neither a SeekHead list nor a Cues list at the beginning of the stream, it SHOULD be considered non-seekable. Even though it is possible to seek forward in the stream, it is NOT RECOMMENDED.

In the context of live radio or web TV, it is possible to “tag” the content while it is playing. The Tags element can be placed between Clusters each time it is necessary. In that case, the new Tags element MUST reset the previously encountered Tags elements and use the new values instead.