--- /dev/null
+MLT Demo Notes
+
+Before running the demo script, make sure you '. setenv' from the parent
+directory. Also, please create clips clip1.dv, clip2.dv, clip3.dv, clip1.mpeg,
+clip2.mpeg, clip3.mpeg, and music1.ogg. It is okay if some of these are
+duplicates. Please make sure clips are at least 500 frames duration.
+
+These notes explain the the concepts presented in each demonstration and
+what details to look for.
+
+First, a note on consumers. When you start the script, the main menu asks
+you to choose a consumer. A consumer is like a viewer, but it could also
+write to a stream/file. The "SDL" consumer is the popular Simple DirectMedia
+Layer audio and video output. The "Westley" consumer generates an XML
+representation of the service network. That can be played directly due to the
+westley producer plugin. See docs/westley.txt for more information. The
+"MainConcept DV" consumer refers to the proprietary MLT plugin required to
+use MLT with MainConcept DV, DVCPro, and MPEG codecs. "/dev/dv1394" refers
+to a device file for transmitting DV over FireWire using the Linux dv1394 kernel
+module. The "BlueFish444" consumer is another proprietary plugin to use
+the BlueFish444 manufactured SDI video/audio output cards with MLT.
+
+And now the demos...
+
+All clips
+
+ Simply builds a playlist containing each video clip, and you can transport
+ between them using j and k keys.
+
+Filter in/out
+
+ A video filter can be applied to a portion of a producer (clip, playlist,
+ or multitrack). This examples shows the greyscale filter.
+
+Watermark
+
+ A graphic can overlay video in realtime with support for alpha channel.
+ This example uses a PNG file with an alpha channel. Distortion is explicitly
+ enabled here so the otherwise circular graphic is scaled to fill the
+ compositing region. By default, compositing honours the aspect ratio of the
+ overlay.
+
+My name is...
+
+ Titles are very easy to composite in realtime. The titler uses Pango
+ with the FreeType2 rendering backend. This means it supports high
+ quality scalable font rendering with anti-aliasing, unicode (UTF-8),
+ and Pango markup capabilities. The compsiting here respects the aspect
+ ratio of the rendered title in the first two title pieces but distorts
+ the final one. This demo also shows the motion and scaling capabilities
+ of the compositor in conjunction with honouring aspect. The compositor
+ is doing field-based rendering. So, when displayed non-progressively
+ with SDL, you can see motion artifacts during animation.
+
+A composite transition
+
+ The compositor also handles video over video as demonstrated in this
+ usage of the compositor to create a special transition. This demonstration
+ also crossfades the audio during the transition! Progressive rendering
+ is explicitly enabled on the compositor due to the poor results that
+ would otherwise occur due to scaling an interleaved video frame and moving
+ the video in a reverse direction horizontally.
+
+Fade in and out
+
+ A simple series of transitions betwen 3 clips using dissolves and audio
+ crossfades. This is easy :-).
+
+Clock in and out
+
+ Wipe transitions are very easy and highly extensible as they are generated
+ using a very convenient lookup table based upon the luma of an image.
+ This image can be a 16 bit PGM (grayscale bitmap) or the luma channel of
+ any video producer. A number of high quality wipes can be downloaded from
+ http://mlt.sf.net/. It also performs field rendering.
+
+Obscure
+
+ A popular requirement in news production is to obscure a face, obscenity,
+ or trademarked logo. This demonstrates using a simple rectangular
+ obscure filter applied to a region of the image. The second example is more
+ advanced and shows using the "region" filter to select the image area and a
+ property of the region filter to "shape" the region using the alpha channel
+ of another image (circle.png) and another property to "filter" the region
+ using the obscure filter.
+
+Audio Stuff
+
+ A music bed sound track can be mixed with a video. The sound track of the
+ video clip has a "floating" amplitude normalisation filter applied.
+ Typically, audio nornmalisation applies a constant gain factor across the
+ entire duration of an audio segment from a single source where the
+ gain factor is automatically determined by anaylsing the maximum "power"
+ or peak levels. However, in news production, a popular requirement is to
+ to dynamically boost the amplitude in soft areas and reduce the amplitude
+ in louder areas. Thus, the gain analysis is performed using a "sliding
+ window" approach. This example also applies a constant gain factor of
+ 0.5 (50%) to the normalised audio of the video clip (to get a nicer
+ mix level).
+
+Audio and Video Levels
+
+ Audio can be normalised by setting a target amplitude level in decibels.
+ A gamma curve can be applied to the luma channel of video.
+
+Shadowed Title and Watermark
+
+ Two instances of the titler are used to create a shadow effect.
+ The aspect ratio of the watermark in this example is not distorted. Since
+ the original image is a circle with square pixels--a computer-generated
+ image--and ITU BT.601 video is not composed of square samples. Therefore,
+ the compositor normalises the pixel aspect ratio of the overlay to the
+ destination image, and the circular image remains circular on the analog
+ video output. Finally, a greyscale filter is applied to the watermark
+ while its opacity is set at 30%.
+
+Station Promo into Story?
+
+ Here is fun demo that might show using a still graphic with some music
+ to introduce a show. A luma wipe with an audio crossfade transitions from
+ the show title or station promotional material.
+
+Voiceover 2 clips with title
+
+ A common news production requirement to have a "voiceover" audio track
+ to a clip or even multiple clips as demonstrated here. Likewise, it is
+ common to place a title caption on the video at the same time! This
+ demo has a little fun with the titler at the sake of practicality :-)
+ The foreground of the title is transparent while the opacity of the
+ background is reduced to blend with the video. Meanwhile, the compositor
+ stretches the image to fill the bottom slice of the video--not suitable
+ for overscan displays ;-)
+
+ Also, pay close attention to the mixing levels of the audio tracks.
+ The audio of the video fades out as the voiceover track (just music
+ in this demo) fades in. Then, the voiceover remains mixed with the
+ ambient audio at a 60% level. Finally, the voiceover fades out smoothly
+ from the 60% level to nothing.
+
+GJ-TTAvantika title
+
+ This demo requires a special TrueType font called Avantika. If you have the
+ font, register it with fontconfig using the fc-cache utility. This
+ demonstrates i18n capabilities of the titler and the alignment capabilities
+ of both the titler and the compositor. The titler centre aligns
+ the two lines of text, and the compositor centre aligns the title
+ horizontally on the frame.
+
+Title over graphic
+
+ You can superimpose a title over a graphic over video! Also,
+ you can apply a luma wipe to the compositor!
+
+Slideshow
+
+ This demo requires any number of JPEG images with the extension ".jpg"
+ in a subdirectory named "Scotland."
+
+Bouncy, Bouncy
+
+ The "watermark" filter encapsulates the compositor, and you have full
+ control over the compositor properties. Who says a watermark can not
+ also be a video?!
+
+Bouncy, Bouncy Ball
+
+ A variation on the above Bouncy, Bouncy demo that applies a shape, or
+ alpha producer, to the the compositing region.
projects / mlt / commitdiff