[Kdenlive-devel] Fwd: mlt jack issues - episode 2

[Dan Dennedy]

On Sun, Aug 5, 2012 at 7:02 AM, Ed Rogalsky <ed.rogalsky at gmail.com> wrote:
> Hi Dan,
>
> the last weeks I thought my job will kill me :-)). But now I had some
> time and here my new results:
>
> 1)  There is one issue with seeking with mlt jack if the consumer
> (sdl_preview) is stopped or paused. The reason is the same as for our
> ugly noise. The function in filter_jackrack.c:
>
> static int jackrack_get_audio( mlt_frame frame, void **buffer,
> mlt_audio_format *format, int *frequency, int *channels, int *samples)
> {
> ...
>
>         if ( pos == mlt_properties_get_position( filter_properties,
> "_jack_seek" ) )
>         {
>                 jack_client_t *jack_client =
> mlt_properties_get_data(filter_properties, "jack_client", NULL );
>                 jack_position_t jack_pos;
>                 jack_transport_query( jack_client, &jack_pos );
>                 double fps = mlt_profile_fps(
> mlt_service_profile(MLT_FILTER_SERVICE(filter) ) );
>                 jack_nframes_t jack_frame = jack_pos.frame_rate * pos / fps;
>                 jack_transport_locate( jack_client, jack_frame );
>                 mlt_properties_set_position( filter_properties,
> "_jack_seek", -1 );
>         }
> ...
> }
>
> is not called and the _jack_seek property is not evaluated. This means
> that seeking on paused consumers is not possible. I think this is the
> common use case - seeking is done on paused consumers.

OK, but when you commence playback after a seek, then the other jack
app seeks and plays. I did not it an important use case to require the
other app to sync while paused. After all, we are paused, so there is
no sound playing. But I guess this use case does help you locate an
interesting area of the audio timelime by going to it in kdenlive.

> Another big issue is resulting from this:
> Seeking in Tracks without or muted audio is not possible at all. Very
> bad for the following use case:
>
> Video is edited in kdenlive and audio in ardour/tractor. In Kdenlive I
> don't have audio at all ==> jack seeking in kdenlive is not possible.

In Shotcut, I do not have this problem because I attach the jackrack
filter to the consumer and I tell the consumer audio_off=1. Then, you
do not need to manually mute tracks.

> In the function:
>
> static void on_jack_seek( mlt_properties owner, mlt_filter filter,
> mlt_position *position )
> {
>         mlt_properties properties = MLT_FILTER_PROPERTIES( filter );
>         mlt_log_verbose( MLT_FILTER_SERVICE(filter), "%s: %d\n",
> __FUNCTION__, *position );
>
>         mlt_properties_set_int( properties, "_sync_guard", 1 );
>         mlt_properties_set_position( properties, "_jack_seek", *position );
>         return; <--- why

I no longer remember. The following code was retained just in case I
changed my mind about something.

>
>         mlt_profile profile = mlt_service_profile( MLT_FILTER_SERVICE(
> filter ) );
>         jack_client_t *jack_client = mlt_properties_get_data(
> properties, "jack_client", NULL );
>         jack_nframes_t jack_frame = jack_get_sample_rate( jack_client );
>         jack_frame *= *position / mlt_profile_fps( profile );
>
>         jack_transport_locate( jack_client, jack_frame );
> }
>
> you return after setting the property "_jack_seek" without calling the
> jack_transport_locate( jack_client, jack_frame ); . I don't understand
> that the sync is not done here. This is done later in the function
> "jackrack_get_audio". But this function is not called in cases mentioned above.
>
> In my private mlt branch I removed the return and the setting of the
> "_jack_seek" property it worked pretty good so far.
>
> Have you got an idea how to solve this issues???

I will experiment with that change and get back to you.

>
> 2)  The crazy noise is now fixed. But on stopping/pausing jack
> transport it takes at least one second until sound stops to play. I
> tried this with shotcut with the same result. In ardour the sound
> stops immediately after pressing the stop key.Is there a way to
> optimize this behaviour? (of course low prio).
>

no comment at this time

>
> 3)  By the way. I played a little bit with shotcut. On my computer I
> have the same behaviour with opengl and jack (I reported this some
> time ago with kdenlive). If shotcut is connected to jack on exit it hangs
> forever. For this I want to try jack1 and perhaps another linux installation.

On my system, I can reproduce this in Shotcut when not using OpenGL. I
will look into it.

>
> PS: With the hack in mlt (removing return ...) and the jack enabled
> kdenlive I made a 15min film. The video was done in kdenlive and the
> audio in ardour. It worked for me so far. I think now I am a step
> closer to the end :-)))

good job!

> regards
> eddrog
>
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