More than one producer+consumer should work. That was a key requirement from the beginning for a multi-channel broadcast playout server. However, focus has changed since that time, and this is rarely exercised. The avformat, qimage, and pixbuf consumers all use mlt_cache via mlt_service, which is a per-process thing: https://github.com/mltframework/mlt/blob/master/src/framework/mlt_service.c#L897 See how it uses mlt_global_properties(): https://github.com/mltframework/mlt/blob/master/src/framework/mlt_factory.c#L56
Why? Think about a composition with a few hundred producers and the ability to seek freely within that composition. Should all of the files handles be held open? In the case of libavcodec and multi-threaded video codecs, should all of the threads remain created? It quickly becomes possible to hit kernel resource limits on open files and child processes per process. Thus, some producers use a cache to limit private context allocations with its associated handles and threads active. Upon a cache miss, it must recreate the private context and re-open and re-initialize things. This repeats what I just said but also describes an environment variable you can use to increase caching for avformat: https://github.com/mltframework/mlt/blob/master/src/modules/avformat/producer_avformat.yml#L18 Try setting that to a higher number using the environment variable or mlt_service_cache_set_size( NULL, "producer_avformat", n ); Also, try testing with other producers such as color and noise. On Tue, Aug 2, 2016 at 5:34 AM Paweł Goliński <golp...@gmail.com> wrote: > Hi, > > For quite some time I’ve been fighting with a curious bug in my consumer. > > Basically in VLMC (Videolan’s video editor) we have Clip Preview and > Project Preview > windows, one for streaming imported clips, the second one for streaming > current project. > My libVLC consumer takes as it’s target widget id, and I have 2 > producer+consumer MLT > pipelines, one for clip preview widget, one for project preview widget. > > The problem is, when trying to run streaming on both these widgets at > once, suddenly > everything starts misbehaving, and it looks like producer connected to my > consumer > (which is avformat for Clip Preview, and avformat+series of filters for > Project Preview) > produces frames at stunningly low rate (like, 30 frames for 10 seconds for > each of the widgets). > > I discovered funny thing today however. When I launch these pipelines with > separate MLT instances > (so using different mlt_repositories), everything works ok… Moreover, when > looking at Shotcut, kdenlive, > I discovered none of these video editors support streaming video to two > widgets at once (in kdenlive, > if you display Project Monitor and Clip Monitor in one kdenlive window, > and play the second one while the > first one is playing, the first one stops). > > This leads to my question. I’m trying to eliminate all possible causes of > my bug, I’ve been looking at my consumer’s > code for quite some time, but it seems to me that the problem may actually > lie in avformat producer (although I may be wrong), > as it just looks that when turning both pipelines on at once, suddenly > mlt_consumer_get_frames() in my consumer start taking a looot > of time (like, more than 100x slower). > > So - is the thing I’m doing supported in MLT (meaning, running two > independent producer+consumer pipelines at once)? > > > Best, > Paweł > > ------------------------------------------------------------------------------ > _______________________________________________ > Mlt-devel mailing list > Mlt-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/mlt-devel >
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