Re: [Mlt-devel] MELT: adding 2 new tracks (video) from a same starting point

[Dan D. <da...@de...>]

On Sat, Apr 10, 2010 at 11:40 AM, Brice Vercoustre <br...@ve...> wrote:
> Hi all,
>
> I'm trying to find the proper command line that would help me insert 2 new tracks (A & B) starting both from the first frame at the same moment (in=0) of a "color:black" background video (640x360, 16:9).
>
> Track "A" should contain a first_video.wmv (640x480, 4:3) with a geometry attribute that would place it on top left bottom as a 160x120 thumbnail (0%,0%:25%x33.33%). It is going to contain the video of a human's performance.
>
> Track "B" should contain a second_video.wmv (640x480, 4:3), also with a geometry attribute that would place it on right  in 480x360 - full height (25%,0%:75%x100%) as the principal video. It is going to contain the VGA output recording of the speaker's PC that displayed a powerpoint presentation.
>
> If the shema above is displayed properly, it should illustrate what kind of result I'm seeking:
>
>      +------------------------------------+
>      |+-------+ +-----------------------+|
>      ||     A     | |                                 ||
>      |+-------+ |               B                ||
>      |               |                                  ||
>      |               |                                  ||
>      |               +-----------------------+|
>      +------------------------------------+
>
>
>
> Here is the command line I tried :
>
> melt color:black length=250 out=250
>
> -track avformat:first_video.wmv in=0 out=250 length=250 -transition composite always_active=1 geometry="0%,0%:25%x33.33%" distort=1 -filter channelcopy to=0 from=1
>
> -track avformat:second_video.wmv in=0 out=250 length=250 -transition composite always_active=1 geometry="25%,0%:75%x100%" distort=1
>
> -consumer avformat:result.mp4 f=mp4 acodec=libfaac ab=92k ac=2 pix_fmt=yuv420p vcodec=libx264 vpre=fastfirstpass minrate=0 b=1000k threads=0 b_strategy=1 subcmp=2 cmp=2 coder=1 flags=+loop flags2=dct8x8 qmax=51 subq=7 qmin=10 qcomp=0.6 qdiff=4 trellis=1 aspect=1.7777 s=640x360
>
>
>
> The result is the B track that takes all the video resolution (the geometry attribute is not respected). If I try the command line with only one of the two track, neither A or B, the result is perfect: I get either the thumbnail in top left corner, or the main video on right.
>
> Please do you know how I can get both track A & B working together? Or must I try something else to get my result?
>
> Thank you so much for your help ;-)
>

A few things need to be done.
1.) Put all transitions after the tracks.
2.) Set track_a and track_b properties on the transitions.
3.) Set a duration on the transitions by setting the out points.

A few remarks:
1.) You do not need to set the length property on anything in the above.
2.) I discourage usage of the distort property on the composite transition.
3.) I encourage usage of the progressive=1 property on the composite transition.
4.) You do not need to explicitly set the producer to use on the video files.

melt color:black out=250 \
-track first_video.wmv out=250 channelcopy to=0 from=1 \
-track second_video.wmv out=250 \
-transition composite geometry="0%,0%:25%x33.33%" out=250 a_track=0
b_track=1 progressive=1 \
-transition composite geometry="25%,0%:75%x100%" a_track=0 b_track=2
out=250 progressive=1

-- 
+-DRD-+