[Icecast] Icecast support for HLS or MPEG-DASH

[Fred Gleason]

On Mar 16, 2022, at 15:08, Chip <chiapas at aktivix.org> wrote:

> And may I ask why you would be so shocked if support for HLS/DASH ever came to Icecast?

Because they are two completely different animals. It would be like comparing a mountain lion to a dolphin. There’re both mammals, but otherwise designed for totally different environments.


> Is it because they are proprietary protocols? But Icecast has support for MP3 and AAC.

The audio codecs are the same, yes. The transports however are utterly different.

ICY/ice delivers a single sequential bitstream to each player. That makes the encoder and player relatively simple and easy to implement, but means that you need a fairly complex “stream splitter” (for lack of a better term) between them to create and manage a separate, unicast bitstream copy for each player. That’s the role that Icecast and its brethren fulfill.

OTOH, HLS/DASH takes that bitstream and splits it into segments of a given length (10 secs/segment is typical) and then posts each segment to a web server. Players download those segments, reassemble them into the original bitstream and then render the content. Since all of this segmentation and reassembly takes place at the endpoints, it makes both the encoder and the player *much* more complex. The advantage though is that the server then can be an ordinary ‘garden variety’ web server, because all you’re doing from the server POV is posting and downloading files. Such files are straightforward to replicate through a CDN, using the same methods that are already well established for replicating web content, whereas for ICY/ice streams you need special server software —e.g. the ‘relay’ functionality in Icecast.

Cheers!


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| Frederick F. Gleason, Jr. |             Chief Developer             |
|                           |             Paravel Systems             |
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