Debug logging

By default ExoPlayer only logs errors. To log player events, the EventLogger class can be used. The additional logging it provides can be helpful for understanding what the player is doing, as well as for debugging playback issues. EventLogger implements AnalyticsListener, so registering an instance with a SimpleExoPlayer is easy:

player.addAnalyticsListener(new EventLogger(trackSelector));

Passing the trackSelector enables additional logging, but is optional and so null can be passed instead.

The easiest way to observe the log is using Android Studio’s logcat tab. You can select your app as debuggable process by the package name ( if using the demo app) and tell the logcat tab to log only for that app by selecting ‘show only selected application’. It’s possible to further filter the logging with the expression EventLogger|ExoPlayerImpl, to get only logging from EventLogger and the player itself.

An alternative to using Android Studio’s logcat tab is to use the console. For example:

adb logcat EventLogger:* ExoPlayerImpl:* *:s

Player information

The ExoPlayerImpl class delivers two important lines about the player version, the device and OS the app is running on and the modules of ExoPlayer that have been loaded:

ExoPlayerImpl: Release 2cd6e65 [ExoPlayerLib/2.12.0] [marlin, Pixel XL, Google, 26] [goog.exo.core, goog.exo.ui, goog.exo.dash]
ExoPlayerImpl: Init 2e5194c [ExoPlayerLib/2.12.0] [marlin, Pixel XL, Google, 26]

Playback state

Player state changes are logged in lines like the ones below:

EventLogger: playWhenReady [eventTime=0.00, mediaPos=0.00, window=0, true, USER_REQUEST]
EventLogger: state [eventTime=0.01, mediaPos=0.00, window=0, BUFFERING]
EventLogger: state [eventTime=0.93, mediaPos=0.00, window=0, period=0, READY]
EventLogger: isPlaying [eventTime=0.93, mediaPos=0.00, window=0, period=0, true]
EventLogger: playWhenReady [eventTime=9.40, mediaPos=8.40, window=0, period=0, false, USER_REQUEST]
EventLogger: isPlaying [eventTime=9.40, mediaPos=8.40, window=0, period=0, false]
EventLogger: playWhenReady [eventTime=10.40, mediaPos=8.40, window=0, period=0, true, USER_REQUEST]
EventLogger: isPlaying [eventTime=10.40, mediaPos=8.40, window=0, period=0, true]
EventLogger: state [eventTime=20.40, mediaPos=18.40, window=0, period=0, ENDED]
EventLogger: isPlaying [eventTime=20.40, mediaPos=18.40, window=0, period=0, false]

In this example playback starts 0.93 seconds after the player is prepared. The user pauses playback after 9.4 seconds, and resumes playback one second later at 10.4 seconds. Playback ends ten seconds later at 20.4 seconds. The common elements within the square brackets are:

  • [eventTime=float]: The wall clock time since player creation.
  • [mediaPos=float]: The current playback position.
  • [window=int]: The current window index.
  • [period=int]: The current period in that window.

The final elements in each line indicate the value of the state being reported.

Media tracks

Track information is logged when the available or selected tracks change. This happens at least once at the start of playback. The example below shows track logging for an adaptive stream:

EventLogger: tracks [eventTime=0.30, mediaPos=0.00, window=0, period=0,
EventLogger:   MediaCodecVideoRenderer [
EventLogger:     Group:0, adaptive_supported=YES [
EventLogger:       [X] Track:0, id=133, mimeType=video/avc, bitrate=261112, codecs=avc1.4d4015, res=426x240, fps=30.0, supported=YES
EventLogger:       [X] Track:1, id=134, mimeType=video/avc, bitrate=671331, codecs=avc1.4d401e, res=640x360, fps=30.0, supported=YES
EventLogger:       [X] Track:2, id=135, mimeType=video/avc, bitrate=1204535, codecs=avc1.4d401f, res=854x480, fps=30.0, supported=YES
EventLogger:       [X] Track:3, id=160, mimeType=video/avc, bitrate=112329, codecs=avc1.4d400c, res=256x144, fps=30.0, supported=YES
EventLogger:       [ ] Track:4, id=136, mimeType=video/avc, bitrate=2400538, codecs=avc1.4d401f, res=1280x720, fps=30.0, supported=NO_EXCEEDS_CAPABILITIES
EventLogger:     ]
EventLogger:   ]
EventLogger:   MediaCodecAudioRenderer [
EventLogger:     Group:0, adaptive_supported=YES_NOT_SEAMLESS [
EventLogger:       [ ] Track:0, id=139, mimeType=audio/mp4a-latm, bitrate=48582, codecs=mp4a.40.5, channels=2, sample_rate=22050, supported=YES
EventLogger:       [X] Track:1, id=140, mimeType=audio/mp4a-latm, bitrate=127868, codecs=mp4a.40.2, channels=2, sample_rate=44100, supported=YES
EventLogger:     ]
EventLogger:   ]
EventLogger: ]

In this example, the player has selected four of the five available video tracks. The fifth video track is not selected because it exceeds the capabilities of the device, as indicated by supported=NO_EXCEEDS_CAPABILITIES. The player will adapt between the selected video tracks during playback. When the player adapts from one track to another, it’s logged in a line like the one below:

EventLogger: downstreamFormat [eventTime=3.64, mediaPos=3.00, window=0, period=0, id=134, mimeType=video/avc, bitrate=671331, codecs=avc1.4d401e, res=640x360, fps=30.0]

This log line indicates that the player switched to the 640x360 resolution video track three seconds into the media.

Decoder selection

In most cases ExoPlayer renders media using a MediaCodec acquired from the underlying platform. When a decoder is initialized, this is logged in lines like the ones below:

EventLogger: videoDecoderInitialized [0.77, 0.00, window=0, period=0, video,]
EventLogger: audioDecoderInitialized [0.79, 0.00, window=0, period=0, audio,]