It’s that time of year again. Time for a new version of our software.

For GA release 1.15.16, we brewed up new fixes and features to help you stream more easily. Here are a few highlights from the release notes.

🧨 Added support for Alpine Linux 3.23

Linux is a kernel, or core component of an operating system, as well as a collection of operating systems. Alpine Linux is a very secure and lightweight distribution, or user-friendly package, of Linux. Upgrading support for Alpine Linux 3.23 means we’re keeping you current with the most recent version of Alpine Linux. 

For streaming applications, using Alpine Linux is popular. Another important use of Alpine Linux is in Docker containers, usually the default distribution (due to Alpine Linux’s small size).

So if Alpine Linux is your ride-or-die OS, Unified has made it easier for you to run Unified Streaming’s platform of products without issues.

🧨 Removed support for Alpine Linux 3.19

Security support for Alpine Linux version 3.19 ended on 1 November 2025. Since the version doesn’t receive security patches anymore, we also no longer support the version. Safety first.

🧨 libfmp4: remove WebVTT cues with invalid durations

Some subtitle authoring tools, or the users thereof, emit subtitle cues with “impossible” timestamps. We’re talking timestamps like “show this cue from 00:12 to 00:06” (negative duration) and “this cue lasts from 12:34 to 12:34” (zero duration). We used to error out on these, but now we print a warning and drop the bad cues instead.

Since there are a lot of poorly written subtitles out there, this fix matters. You can’t fix all errors. Sometimes you have to make do with what you have.

🧨dash: added --mpd.disable_sidecar_webvtt option to disable adding a WebVTT sidecar adaptation set

“Sidecars” are an alternative way to deliver subtitles, next to the regular mechanism of delivering them in fragmented MP4 files (usually CMAF). Historically, if you were using WebVTT for the subtitles, we always added such a sidecar adaptation set to DASH manifests. This was not the case for TTML subtitles, though. When creating the server manifest, you would have to specify –mpd.sidecar_ttml.

In the WebVTT subtitles world, there was no method of getting rid of the sidecar if people didn’t want it, except by deploying Manifest Edit.

So we added the –mpd.disable_sidecar_webvtt option to disable WebVTT sidecars. By the way, a customer asked for this fix, as the problem annoyed them. And it annoyed us, too. No more annoyance.

🧨 mp4split: preserve timed metadata when producing HLS playlists from TTML subtitles packaged in CMAF files

You can add timed metadata to CMAF files, and then produce HLS playlists from those CMAF files. The HLS playlists will contain the timed metadata as so-called EXT-X-DATERANGE tags. 

Used to be that when you produced HLS playlists from CMAF files, with TTML subtitles as the source, the timed metadata was not emitted correctly. Now that’s been fixed.

Little trivia for you. HLS presentations typically used WebVTT for their subtitles. These days, TTML is up-and-coming. For both types of subtitles, timed metadata can now be used in the same way.

🧨 origin: added --track_groupid option for server manifests

HLS has so-called rendition groups, different renditions of the same content. One example would be audio tracks with different languages. Rendition groups are identified by their GROUP-ID values. Unified Origin attempts, automatically, to determine such groups according to the Apple recommendations. Sometimes, though, the result is not what the customer wants. We’ve added a –track_groupid option that overrides Origin’s own choice, so customers can now place tracks in any group they would like.

Some customers like to group tracks in ways that don’t hew to Apple’s recommendations. Naturally, we like to please everybody.

🧨 libfmp4: fixed --track_bitrate=max to set the systemBitrate to the max bitrate (instead of the average) in the server manifest

Unified Packager has an option called –track_bitrate. This option overrides the average bitrate of a given track. If you give it the special value –track_bitrate=max, the maximum (or peak) bitrate will be used instead. In some cases, this would lead to an erroneous value of 4294967295, which is the highest value an unsigned 32-bit integer can have.

We fixed this so it now works correctly. This helps, because bitrate values of 4.2 gigabits per second are abnormally high, and will probably confuse players.

That's the end

Sorry for cutting things short. But we don't want to tax your attention span.

For more info, and for the full list of changes in the GA, check out the release notes here.

If you have questions, please email us at sales@unified-streaming.com.