Error on looped video in Demo

[Kabaril]

I ran the VideoPlayback.DesktopGL Demo, with the VideoPlayer on loop, after a couple minutes it threw an ApplicationException in VideoPlayer.DecodingThread on line 98, with the message: Cannot access disposed object

[hozuki]

Looks like a rare racing condition. I'll look into this.

[BrianBergh]

I too get a nasty exception when looping or restarting. Its random but i get it every 2 or 3 loops no matter the video source. Its a pointer exception related to a buffer in audio, it says.

[hozuki]

@BrianBergh I tested multiple times and this problem did occur, but it's rare. It seems sometimes dstData[0] (in FFmpegHelper.TransmitAudioFrame) sometimes gets null from av_samples_alloc or swr_convert. I don't know which one because after I set the breakpoint the bug just hid itself. 😞 Needs more testing though. However the bug is not the same as what OP reported.

[BrianBergh]

This is the exception i get (i get it every time i set loop to true) System.NullReferenceException HResult=0x80004003 Message=Object reference not set to an instance of an object. Source=MonoGame.Framework StackTrace: at Microsoft.Xna.Framework.Audio.DynamicSoundEffectInstance.OnBufferEnd(IntPtr obj) at SharpDX.XAudio2.SourceVoice.VoiceCallbackImpl.SharpDX.XAudio2.VoiceCallback.OnBufferEnd(IntPtr context) at SharpDX.XAudio2.VoiceShadow.VoiceVtbl.OnBufferEndImpl(IntPtr thisObject, IntPtr address)

[hozuki]

Does this still happen using new looping mechanism?

[BrianBergh]

Nope, didn't know there were any changes to the subject. Will test it as soon as possible.

[BrianBergh]

I am unable to start the test project WindowsDX, i get this exception: System.EntryPointNotFoundException: 'Could not find the entrypoint for avformat_alloc_context.' I have copied the ffmpeg dll's, still it wont work.

[hozuki]

I am unable to start the test project WindowsDX, i get this exception: System.EntryPointNotFoundException: 'Could not find the entrypoint for avformat_alloc_context.' I have copied the ffmpeg dll's, still it wont work.

Maybe because of dll not found or version mismatch?

• The dlls should be placed in x86 and/or x64 (names depend on arguments of InitializeFFmpeg()).
• Also note the version of FFmpeg, it should be 3.4 (with major versions displayed in usage). As an alternative, you can update FFmpeg.AutoGen to a newer version, and choose corresponding FFmpeg dlls. Anyway, the versions must match. See FFmpeg's versioning rules.

[BrianBergh]

Hi, after updating the nuget package "FFmpeg.AutoGen" it all worked :)

• Not i will test the loop function :P

[BrianBergh]

Hi Hozuki. Loop seems a lot more stable now, however, when using the "Replay()" function a few times, i got this exception:

After retrying a few times, i got this exception:

at Microsoft.Xna.Framework.Audio.DynamicSoundEffectInstance.SubmitBuffer(Byte[] buffer) at MonoGame.Extended.VideoPlayback.DecodeContext.ReadAudioUntilPlaybackIsAfter(DynamicSoundEffectInstance sound, Double presentationTime) in D:\Development\DotNet\ext_git\MonoGame.Extended2\Sources\MonoGame.Extended.VideoPlayback\DecodeContext.cs:line 548 at MonoGame.Extended.Framework.Media.VideoPlayer.DecodingThread.ThreadProc() in D:\Development\DotNet\ext_git\MonoGame.Extended2\Sources\MonoGame.Extended.VideoPlayback\Media\VideoPlayer.DecodingThread.cs:line 119

I don't care about the Replay() function, but it seems that the exception i get from the Replay() is the same i saw in "Loop" mode earlier.

I will continue to test the loop, to see if that can be provoked to produce the exception as well.

[hozuki]

The ObjectDisposedException is caused by accessing _soundEffectInstance in both main thread and decoding thread without "single access" guarantee. It should be fixed in 9baac981d52e76e7bf811a345b2847fb9c625677. (But pessimistic locking spreads everywhere, which may have a little impact on performance. Since the decoding thread is properly terminated in Replay(), you can consider removing those locks and leaving sound-related properties non-thread-safe in exchange of performance.)

And you are right. Looping was emulated by calling Replay() when the video ends.

About duplicate key, do you more information on the exception?

[BrianBergh]

Hi Hozuki. I thought so :)

Here is a more detailed exception on the "Key already exists" at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource) at System.Collections.Generic.SortedList2.Add(TKey key, TValue value) at MonoGame.Extended.VideoPlayback.Extensions.SortedListExtensions.Enqueue[TKey,TValue](SortedList2 list, TKey key, TValue value) in D:\Development\DotNet\ext_git\MonoGame.Extended2\Sources\MonoGame.Extended.VideoPlayback\Extensions\SortedList`2Extensions.cs:line 19 at MonoGame.Extended.VideoPlayback.DecodeContext.TryFetchVideoFrames(Int32 count) in D:\Development\DotNet\ext_git\MonoGame.Extended2\Sources\MonoGame.Extended.VideoPlayback\DecodeContext.cs:line 746 at MonoGame.Extended.VideoPlayback.DecodeContext.ReadVideoUntilPlaybackIsAfter(Double presentationTime) in D:\Development\DotNet\ext_git\MonoGame.Extended2\Sources\MonoGame.Extended.VideoPlayback\DecodeContext.cs:line 407 at MonoGame.Extended.Framework.Media.VideoPlayer.DecodingThread.ThreadProc() in D:\Development\DotNet\ext_git\MonoGame.Extended2\Sources\MonoGame.Extended.VideoPlayback\Media\VideoPlayer.DecodingThread.cs:line 122

Its actually easy to reproduce, start a longer video that the rabit one, and press R a few times.

[BrianBergh]

Hi again. Not sure if my previous post had code aligned, but this is from the latest head:

[BrianBergh]

Hi, i've just tested with a simple (but not necessary the best) solution:

It does the trick, now i can SPAM Replay as much as i like, without any issues :)

[hozuki]

@BrianBergh Thank you. I pushed the commit which fixes

• this problem (duplicate key)
• empty audio buffer queue when calling Stop()

[BrianBergh]

Great, thank you @hozuki :)