Re-evaluate + refine ExoPlayer's default buffer policy

[WeiChungChang]

Hi all:

I am testing the streaming and find the buffering mechanism is interesting.

By default, the maxBufferUs & minBufferUs are 30 & 15 seconds respectively.

accordingly,
isBuffering = bufferTimeState == BELOW_LOW_WATERMARK || (bufferTimeState == BETWEEN_WATERMARKS && isBuffering && !targetBufferSizeReached);
Typically we will continue buffering until the amount of buffering data is over 30 seconds.
Then it stops buffering to wait until the amount of buffering data is less than 15 seconds and re-fetch again when.

I am wondering what is the purpose it is designed for?
I can not figure out a scenario when it has gains from this policy...
Is it make sense if we just simply do download once the buffering data is less than 30 seconds?
Instead of current policy which waits to the buffering data is less than 15 seconds

Does someone know the intention for it?
Thanks.

[rlatapy-gpsw]

Hi
Same problem/question..
And there is also a constant which limit the buffer size, if I well understand.

What is the proper way to get an "unlimited" buffer in order to buffer the whole video ?

[ojw28]

There are arguments that mobile carriers prefer this kind of traffic pattern over their networks (i.e. bursts rather than drip-feeding). Which is an important consideration given ExoPlayer is used by some very popular services. It may also be more battery efficient.

Whether these arguments are still valid is something we should probably take another look at fairly soon, since the information we used when making this decision is 3-4 years old now. We should also figure out whether we should adjust the policy dynamically based on network type (e.g. even if the arguments are still valid, they may only hold for mobile networks and not for WiFi).

Let's use this issue to track taking another look.

@rlatapy-gpsw - You can't have "unlimited" buffer. Devices are fundamentally constrained. If you want this kind of functionality you probably need to implement media downloading. ExoPlayer doesn't implement download functionality (at least for now), but will happily play downloaded media once you've downloaded it. In any case, your question is different, let's not use this issue for it.

[ojw28]

Reassigning as this is likely to need a performance experiment.

[tonihei]

It's already on the list of potential experiments. Although no experiment with Exoplayer can detect if such a setting makes network operators unhappy :). But the influence on buffer rate and battery usage would be interesting to see.

[jemshit]

Is it make sense if we just simply do download once the buffering data is less than 30 seconds?

minBufferMs=30000L
maxBufferMs=30000L