Recommendations to reduce startup time on low-end TV devices (≈10s on Live & VOD)

[testeur-990]

We are currently facing long startup times on several low-end Smart TV devices .
The startup time is around 10s for both Live and VOD streams

We would like to know if you have recommended dash.js settings or best practices to optimize and reduce the startup time specifically on low-end devices.

Thanks in advance.

[dsilhavy]

Can you narrow down what causes the long startup times? Some ideas:

• How long does the parsing of the MPD take?
• What is the size of the MPD? Specifically, are you using SegmentTimeline with a reoccurring pattern in the signaling and a large DVR window leading to large MPD sizes?
• Do you use external WebVTT subtitles? The parsing of these files can also take a significant amount of time
• What is the duration of the segments, especially what is the GoP size? Decoding the frame at the specified startime can take some time depending on the GoP size
• Are you playing with a low latency, potentially leading to the player required to wait for some time to find the right start segment?
• Do you specify an initialBufferLevel ?

[testeur-990]

Hello @dsilhavy ,
Here are the answers to your questions for this application:

Regarding the MPD:

=>There is no r= attribute in the SegmentTimeline.

=>SegmentTemplate durations are:

• Text: duration="2000000"

• Audio: duration="96000"

• Video: duration="25600"

=>For live content, we have a very large DVR window:
timeShiftBufferDepth="PT604800S" .

External WebVTT subtitles:
No, this application does not use external WebVTT files.

Low-latency mode:
We do not use low-latency mode.
This mechanism does not work reliably on low-end TV devices, so LL-DASH is disabled.

InitialBufferLevel:
We noticed that initialBufferLevel is only applied when dash.js autoplay = true.
In our case, autoplay is handled at the application layer, so even if we set this parameter, dash.js does not apply it with the current code path.
We are checking how we can apply this setting even when autoplay is false.

Based on the code in _onBufferLevelUpdated, if initialBufferLevel is not specified, playback should normally start immediately, as soon as the first playable data is available no?

If you have any recommendations or player configurations that could help reduce startup time on low-end devices, please feel free to share them.