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

[Ed Rogalsky]

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.

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 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


        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???


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).



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.


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 :-)))

regards
eddrog