Android MediaPlayer - Sometimes No Video is Played Even Though Audio Plays
I am developing an Android App and I'm using the Android SDK's MediaPlayer to play some videos in my app. When I play the video in my app, about one out of five times, the audio plays without video. It's not a simple coding error because most of the time the video plays perfectly.
I have considered that a race condition in my code caused the bug. However, I added a number of debug statements and everything seems to be set up properly when the video does not play.
I have scanned the web and SO trying to find solutions but none have been adequate (see below).
Has anyone run into this type of problem before? If so, what did you do?
Similar Questions:
android media player shows audio but no video
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Some More Details:
- I've come across this bug on two phones. On a Samsung Charge video plays 80% of the time and 20% of the time there's audio but no video. On a T-Mobile Comet it's much worse; video only plays about 10% of the time.
- It's not a problem with the file, I've tried various video files and codecs and get the same issues.
- It's not a problem with the storage medium. I've tried playing the video when it was stored on internal storage and the sdcard, neither makes a difference. I have even tried reading some of the file before playing it, hoping that the system will cache it, but that doesn't seem to help either.
Update:
I've been debugging this and looking through logcat. I've found that when the video works, something like the following appears in logcat:
09-28 00:09:03.651: VERBOSE/PVPlayer(10875): setVideoSurface(0x65638)
But when video doesn't play, it looks like there's a null entry:
09-28 00:03:35.284: VERBOSE/PVPlayer(10875): setVideoSurface(0x0)
Update 2:
When the video fails to play, the function MediaPlayer.OnInfoListener with parameters what==MEDIA_ERROR_UNKNOWN(0x1) and extra==35. I looked through the Android code-base to try to determine what unknown error 35 means. I came across the file pv_player_interface.h, which indicates that error code 35 corresponds to something called a PVMFInfoTrackDisable. I googled that term which brought me to a file called pvmf_return_codes.pdf. That file gave me the following unintelligible explanation:
4.34. PVMFInfoTrackDisable
Notification that paticular track is disable. This one is on a per track basis. For uncompressed audio/video formats, during the process of selecting tracks available in content, if the decoder doesn't support the track, a PVMFInfoTrackDisable event is sent. The event, if necessary, will be sent once per track.
I feel like I've gone a long way, but am no closer to finding an answer... still investigating.
Answer
I solved the problem, albeit in a totally hackish way. There are two problems actually:
The Evil Info 35 Message: I found that occasionally MediaPlayer.OnInfoListener will get called with extra==35. When this happens, you're screwed and the video will not play properly. I have no idea what causes it. The only fix I found was to try restarting the video and going through the whole prepareAsync process over again. Video playback usually works the second time.
Video Size Not Set: Even after MediaPlayer.OnPreparedListener gets issued (or equivalently prepare() returns) the video size may not be been set. The video size will usually be set a couple of miliseconds after prepare returns, but for a few moments it is in a nebulous state. If you call MediaPlayer.start() before the video size is set, then playback will sometimes (but not always) fail. There are two potential solutions to this: (1) poll MediaPlayer.getVideoHeight() or getVideoWidth() until they're non-zero or (2) wait until OnVideoSizeChangedListener is called. Only after one of these two events, should you call start().
With these two fixes, video playback is much more consistent. It's very likely that these problems are bugs with my phones (Samsung Charge and a T-Mobile Comet) so I won't be surprised if there are different, but similar problems on other phones.