Prevent cordova-plugin-playlist from buffering all tracks at once

Question

I've been trying to solve this issue for a few weeks now. The issue revolves around a Cordova plugin called cordova-plugin-playlist that utilizes AVQueuePlayer.

The issue is that when a large number of tracks (30+) are added, several of the tracks time out when attempting to buffer. Because of this, AVQueuePlayer is only able to play some of the tracks that I'm attempting to load (it just skips the error tracks when attempting to play them). The tracks that time out are always random. Attempting to add only the first 15 or so tracks from the same list succeeds, so it appears to be directly related to the number of tracks being added.

What I've figured out by logging the requests to my server is that AVQueuePlayer is attempting to buffer all of the tracks all at once, rather than buffering only the current and maybe the next track. When there are 20 or fewer tracks, all of the tracks load and play fine, but when there are 30 or more, the request seems to be too much to handle, and the requests begin to time out before some of the tracks are able to load.

All of the tracks are added via AVQueuePlayer's insertItem method. Is there something about this method that causes a track to immediately begin buffering as soon as it is added? Is there a way to prevent this behavior? I would like only the current and next tracks to buffer. Or am I fundamentally misunderstanding something? Thanks in advance for all your help!

score 0 · Answer 1 · answered Dec 05 '18 at 17:31

I've solved the issue. In case it helps anyone, it wasn't an issue with AVQueuePlayer itself, but rather with the subclass AVBidirectionalQueuePlayer included with the cordova-plugin-playlist plugin. The issue lies within the overridden insertItem method in AVBidirectionQueuePlayer.m (line 217 in my case).

if (CMTIME_IS_NUMERIC(item.duration)) {
    NSLog(@"duration: %5.2f", (double) CMTimeGetSeconds(item.duration));
        if (CMTimeCompare(_estimatedDuration, kCMTimeZero) == 0)
            _estimatedDuration = item.duration;
        else
            _estimatedDuration = CMTimeAdd(_estimatedDuration, item.duration);
}

The item.duration call triggers the track to load (and it's called each time a track is added, so it triggers ALL of the tracks to load), which is fine for a smaller number of tracks, but with 30+ tracks, some an hour or longer, my server was overloaded and the requests were timing out.

In my particular instance, it seems that item.duration is never NUMERIC here anyway, so my solution was to comment out the IF statement entirely.

Prevent cordova-plugin-playlist from buffering all tracks at once

1 Answers1