[PATCH 5/6] mfmediaengine: Close the media session on shutdown.

[Derek Lesho]

On 1/5/22 06:09, Nikolay Sivov wrote:
>
>
> On 1/4/22 20:35, Derek Lesho wrote:
>>     failed:
>> @@ -1297,6 +1302,7 @@ static void free_media_engine(struct 
>> media_engine *engine)
>>       }
>>       SysFreeString(engine->current_source);
>>       DeleteCriticalSection(&engine->cs);
>> +    CloseHandle(engine->session_closed);
>>       free(engine->video_frame.buffer);
>>       free(engine);
>>   }
>> @@ -1956,6 +1962,8 @@ static HRESULT WINAPI 
>> media_engine_Shutdown(IMFMediaEngine *iface)
>>       else
>>       {
>>           media_engine_set_flag(engine, FLAGS_ENGINE_SHUT_DOWN, TRUE);
>> +        IMFMediaSession_Close(engine->session);
>> +        WaitForSingleObject(engine->session_closed, INFINITE);
>>           IMFMediaSession_Shutdown(engine->session);
>>       }
>
> Could you explain what does this fix?

::Close releases the queued topology object, ::Shutdown doesn't. 
::Release also closes the topology object, but there's a circular 
dependency here as the sample grabber sink node in the queued topology 
references the sample grabber media sink object, which references the 
sample grabber callback object, which, in the case of the media engine, 
contributes to the reference count of the media engine, and the media 
engine only releases the media session once it is fully released.

Additionally, the documentation advises that you ::Close a session 
before shutting it down. 
https://docs.microsoft.com/en-us/windows/win32/medfound/step-7--shut-down-the-media-session

>> LeaveCriticalSection(&engine->cs);
>> @@ -2451,6 +2459,7 @@ static HRESULT init_media_engine(DWORD flags, 
>> IMFAttributes *attributes, struct
>>       engine->duration = NAN;
>>       engine->video_frame.pts = MINLONGLONG;
>>       InitializeCriticalSection(&engine->cs);
>> +    engine->session_closed = CreateEventW(NULL, TRUE, FALSE, NULL);
>>         hr = IMFAttributes_GetUnknown(attributes, 
>> &MF_MEDIA_ENGINE_CALLBACK, &IID_IMFMediaEngineNotify,
>>               (void **)&engine->callback);
>
>