Live Sync fails over several hours - SNTP time update

Version

Media3 1.1.1

More version details

Run two Android TV streamers side by side with a set latency target (either via <ServiceDescription> or using MediaItem.Builder(). setLiveConfiguration(...)). Observe they will lock in to nearly the frame from the start.

After several hours of runtime they will drift, potentially 100's of milliseconds apart. The cause is the inaccuracy of System.elaspedTime() over

Devices that reproduce the issue

Google TV w/Chromecast
Evolution e*Stream 4k
Likely many others with SEI / AmLogic SoC

Devices that do not reproduce the issue

No response

Reproducible in the demo app?

Yes

Reproduction steps

Play media (on request) for several hours (longer give more error)
Observe sync gradually declines

Expected result

With the proposed fix in the pull request the streams have played over 10 hours with no errors.

Actual result

streams are out of sync in 5 or so hours. Note this may seem like a long time, but imagine a bar or health club setting. Also, there is no recovery by changing the channel (requires force-stop of the application hosting ExoPlayer)

Media

on request, not you may really need at least 5 hours of playback to see the issue.

Bug Report

[ ] You will email the zip file produced by adb bugreport to android-media-github@google.com after filing this issue.

Logging of time from several hours of playback on an SEI Android TV boxes:

10-02 20:42:06.081 17353 17353 D ExoGeekStat: Now (delta) [NTP: 2023-10-02T20:42:06.136, Window: 2023-10-02T20:42:06.138 (2), currentTimeMillis(): 2023-10-02T20:42:06.076 (-60)
10-02 20:42:12.070 17353 17353 D ExoGeekStat: Now (delta) [NTP: 2023-10-02T20:42:12.129, Window: 2023-10-02T20:42:12.129 (0), currentTimeMillis(): 2023-10-02T20:42:12.067 (-62)
10-02 20:42:18.057 17353 17353 D ExoGeekStat: Now (delta) [NTP: 2023-10-02T20:42:18.117, Window: 2023-10-02T20:42:18.116 (-1), currentTimeMillis(): 2023-10-02T20:42:18.054 (-63)
10-02 20:42:24.056 17353 17353 D ExoGeekStat: Now (delta) [NTP: 2023-10-02T20:42:24.116, Window: 2023-10-02T20:42:24.116 (0), currentTimeMillis(): 2023-10-02T20:42:24.054 (-62)
...
10-03 08:30:38.037 17353 17353 D ExoGeekStat: Now (delta) [NTP: 2023-10-03T08:30:38.210, Window: 2023-10-03T08:30:38.098 (-112), currentTimeMillis(): 2023-10-03T08:30:38.036 (-174)
10-03 08:30:44.041 17353 17353 D ExoGeekStat: Now (delta) [NTP: 2023-10-03T08:30:44.212, Window: 2023-10-03T08:30:44.101 (-111), currentTimeMillis(): 2023-10-03T08:30:44.039 (-173)
10-03 08:30:50.040 17353 17353 D ExoGeekStat: Now (delta) [NTP: 2023-10-03T08:30:50.212, Window: 2023-10-03T08:30:50.101 (-111), currentTimeMillis(): 2023-10-03T08:30:50.039 (-173)
10-03 08:30:56.073 17353 17353 D ExoGeekStat: Now (delta) [NTP: 2023-10-03T08:30:56.246, Window: 2023-10-03T08:30:56.134 (-112), currentTimeMillis(): 2023-10-03T08:30:56.072 (-174)

The logged values are:

Now — from a seperate NTP client that does update every 10 minutes
Window — from the query NTP once value in Window.getCurrentUnixTimeMs()
currentTimeMillis() — value from System.currentTimeMillis()

Here is the logging code snippet:

            SNTPClient.getDate(TimeZone.getDefault(), new SNTPClient.Listener() {
              @Override
              public void onTimeResponse(long ntpDate, Exception ex) {
                timeCheckActive = false;
                Timeline timeline = player.getCurrentTimeline();
                if (!timeline.isEmpty()) {
                  StringBuilder logString = new StringBuilder();
                  Formatter formatter = new Formatter(logString);
                  int windowIndex = player.getCurrentWindowIndex();
                  Timeline.Window window = timeline.getWindow(windowIndex, new Timeline.Window());
                  long currentUnixTimeMs = window.getCurrentUnixTimeMs();
                  long currentTimeMillis = System.currentTimeMillis();
                  formatter.format("Now (delta) [NTP: %1$tFT%1$tT.%1$tL, Window: %2$tFT%2$tT.%2$tL (%3$d), currentTimeMillis(): %4$tFT%4$tT.%4$tL (%5$d)",
                      ntpDate,
                      currentUnixTimeMs,
                      currentUnixTimeMs - ntpDate,
                      currentTimeMillis,
                      currentTimeMillis - ntpDate);
                  Log.d(TAG, logString.toString());
                }
              }
          });

The SNTPClient is the ASOP version

androidx / media