1---
2title: Debug logging
3---
4
5By default ExoPlayer only logs errors. To log player events, the `EventLogger`
6class can be used. The additional logging it provides can be helpful for
7understanding what the player is doing, as well as for debugging playback
8issues. `EventLogger` implements `AnalyticsListener`, so registering an instance
9with an `ExoPlayer` is easy:
10
11```
12player.addAnalyticsListener(new EventLogger(trackSelector));
13```
14{: .language-java}
15
16Passing the `trackSelector` enables additional logging, but is optional and so
17`null` can be passed instead.
18
19The easiest way to observe the log is using Android Studio's [logcat tab][]. You
20can select your app as debuggable process by the package name (
21`com.google.android.exoplayer2.demo` if using the demo app) and tell the logcat
22tab to log only for that app by selecting 'show only selected application'. It's
23possible to further filter the logging with the expression
24`EventLogger|ExoPlayerImpl`, to get only logging from `EventLogger` and the
25player itself.
26
27An alternative to using Android Studio's logcat tab is to use the console. For
28example:
29
30~~~
31adb logcat EventLogger:* ExoPlayerImpl:* *:s
32~~~
33{: .language-shell}
34
35### Player information ###
36
37The `ExoPlayerImpl` class delivers two important lines about the player version,
38the device and OS the app is running on and the modules of ExoPlayer that have
39been loaded:
40
41```
42ExoPlayerImpl: Release 2cd6e65 [ExoPlayerLib/2.12.0] [marlin, Pixel XL, Google, 26] [goog.exo.core, goog.exo.ui, goog.exo.dash]
43ExoPlayerImpl: Init 2e5194c [ExoPlayerLib/2.12.0] [marlin, Pixel XL, Google, 26]
44```
45
46### Playback state ###
47
48Player state changes are logged in lines like the ones below:
49
50```
51EventLogger: playWhenReady [eventTime=0.00, mediaPos=0.00, window=0, true, USER_REQUEST]
52EventLogger: state [eventTime=0.01, mediaPos=0.00, window=0, BUFFERING]
53EventLogger: state [eventTime=0.93, mediaPos=0.00, window=0, period=0, READY]
54EventLogger: isPlaying [eventTime=0.93, mediaPos=0.00, window=0, period=0, true]
55EventLogger: playWhenReady [eventTime=9.40, mediaPos=8.40, window=0, period=0, false, USER_REQUEST]
56EventLogger: isPlaying [eventTime=9.40, mediaPos=8.40, window=0, period=0, false]
57EventLogger: playWhenReady [eventTime=10.40, mediaPos=8.40, window=0, period=0, true, USER_REQUEST]
58EventLogger: isPlaying [eventTime=10.40, mediaPos=8.40, window=0, period=0, true]
59EventLogger: state [eventTime=20.40, mediaPos=18.40, window=0, period=0, ENDED]
60EventLogger: isPlaying [eventTime=20.40, mediaPos=18.40, window=0, period=0, false]
61```
62
63In this example playback starts 0.93 seconds after the player is prepared. The
64user pauses playback after 9.4 seconds, and resumes playback one second later at
6510.4 seconds. Playback ends ten seconds later at 20.4 seconds. The common
66elements within the square brackets are:
67
68* `[eventTime=float]`: The wall clock time since player creation.
69* `[mediaPos=float]`: The current playback position.
70* `[window=int]`: The current window index.
71* `[period=int]`: The current period in that window.
72
73The final elements in each line indicate the value of the state being reported.
74
75### Media tracks ###
76
77Track information is logged when the available or selected tracks change. This
78happens at least once at the start of playback. The example below shows track
79logging for an adaptive stream:
80
81```
82EventLogger: tracks [eventTime=0.30, mediaPos=0.00, window=0, period=0,
83EventLogger:   MediaCodecVideoRenderer [
84EventLogger:     Group:0, adaptive_supported=YES [
85EventLogger:       [X] Track:0, id=133, mimeType=video/avc, bitrate=261112, codecs=avc1.4d4015, res=426x240, fps=30.0, supported=YES
86EventLogger:       [X] Track:1, id=134, mimeType=video/avc, bitrate=671331, codecs=avc1.4d401e, res=640x360, fps=30.0, supported=YES
87EventLogger:       [X] Track:2, id=135, mimeType=video/avc, bitrate=1204535, codecs=avc1.4d401f, res=854x480, fps=30.0, supported=YES
88EventLogger:       [X] Track:3, id=160, mimeType=video/avc, bitrate=112329, codecs=avc1.4d400c, res=256x144, fps=30.0, supported=YES
89EventLogger:       [ ] Track:4, id=136, mimeType=video/avc, bitrate=2400538, codecs=avc1.4d401f, res=1280x720, fps=30.0, supported=NO_EXCEEDS_CAPABILITIES
90EventLogger:     ]
91EventLogger:   ]
92EventLogger:   MediaCodecAudioRenderer [
93EventLogger:     Group:0, adaptive_supported=YES_NOT_SEAMLESS [
94EventLogger:       [ ] Track:0, id=139, mimeType=audio/mp4a-latm, bitrate=48582, codecs=mp4a.40.5, channels=2, sample_rate=22050, supported=YES
95EventLogger:       [X] Track:1, id=140, mimeType=audio/mp4a-latm, bitrate=127868, codecs=mp4a.40.2, channels=2, sample_rate=44100, supported=YES
96EventLogger:     ]
97EventLogger:   ]
98EventLogger: ]
99```
100
101In this example, the player has selected four of the five available video
102tracks. The fifth video track is not selected because it exceeds the
103capabilities of the device, as indicated by `supported=NO_EXCEEDS_CAPABILITIES`.
104The player will adapt between the selected video tracks during playback. When
105the player adapts from one track to another, it's logged in a line like the one
106below:
107
108```
109EventLogger: 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]
110```
111
112This log line indicates that the player switched to the 640x360 resolution video
113track three seconds into the media.
114
115### Decoder selection ###
116
117In most cases ExoPlayer renders media using a `MediaCodec` acquired from the
118underlying platform. When a decoder is initialized, this is logged in lines like
119the ones below:
120
121```
122EventLogger: videoDecoderInitialized [0.77, 0.00, window=0, period=0, video, OMX.qcom.video.decoder.avc]
123EventLogger: audioDecoderInitialized [0.79, 0.00, window=0, period=0, audio, OMX.google.aac.decoder]
124```
125
126[logcat tab]: https://developer.android.com/studio/debug/am-logcat
127