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authorwm4 <wm4@nowhere>2012-12-21 18:49:54 +0100
committerwm4 <wm4@nowhere>2012-12-28 13:43:59 +0100
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DOCS: document EDL format
This is taken from the commit message of 968154ba77f8, with some fixes to make it valid RST.
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+Format of mplayer2 EDL files
+============================
+
+The first line in the file must be ``mplayer EDL file, version 2``.
+The rest of the lines belong to one of these classes:
+
+1) lines specifying source files
+2) empty lines
+3) lines specifying timeline segments.
+
+Lines beginning with ``<`` specify source files. These lines first
+contain an identifier used to refer to the source file later, then the
+filename separated by whitespace. The identifier must start with a
+letter. Filenames that start or end with whitespace or contain
+newlines are not supported.
+
+On other lines ``#`` characters delimit comments. Lines that contain
+only whitespace after comments have been removed are ignored.
+
+Timeline segments must appear in the file in chronological order. Each
+segment has the following information associated with it:
+
+- duration
+- output start time
+- output end time (= output start time + duration)
+- source id (specifies the file the content of the segment comes from)
+- source start time (timestamp in the source file)
+- source end time (= source start time + duration)
+
+The output timestamps must form a continuous timeline from 0 to the
+end of the last segment, such that each new segment starts from the
+time the previous one ends at. Source files and times may change
+arbitrarily between segments.
+
+The general format for lines specifying timeline segments is
+[output time info] source_id [source time info]
+source_id must be an identifier defined on a ``<`` line. Both the time
+info parts consists of zero or more of the following elements:
+
+1) ``timestamp``
+2) ``-timestamp``
+3) ``+duration``
+4) ``*``
+5) ``-*``
+
+, where ``timestamp`` and ``duration`` are decimal numbers (computations
+are done with nanosecond precision). Whitespace around ``+`` and ``-`` is
+optional. 1) and 2) specify start and end time of the segment on
+output or source side. 3) specifies duration; the semantics are the
+same whether this appears on output or source side. 4) and 5) are
+ignored on the output side (they're always implicitly assumed). On the
+source side 4) specifies that the segment starts where the previous
+segment *using this source* ended; if there was no previous segment
+time 0 is used. 5) specifies that the segment ends where the next
+segment using this source starts.
+
+Redundant information may be omitted. It will be filled in using the
+following rules:
+
+- output start for first segment is 0
+- two of [output start, output end, duration] imply third
+- two of [source start, source end, duration] imply third
+- output start = output end of previous segment
+- output end = output start of next segment
+- if ``*``, source start = source end of earlier segment
+- if ``-*``, source end = source start of a later segment
+
+As a special rule, a last zero-duration segment without a source
+specification may appear. This will produce no corresponding segment
+in the resulting timeline, but can be used as syntax to specify the
+end time of the timeline (with effect equal to adding -time on the
+previous line).
+
+Examples::
+
+ mplayer EDL file, version 2
+ < id1 filename
+
+ 0 id1 123
+ 100 id1 456
+ 200 id1 789
+ 300
+
+All segments come from the source file ``filename``. First segment
+(output time 0-100) comes from time 123-223, second 456-556, third
+789-889.
+
+::
+
+ mplayer EDL file, version 2
+ < f filename
+ f 60-120
+ f 600-660
+ f 30- 90
+
+Play first seconds 60-120 from the file, then 600-660, then 30-90.
+
+::
+
+ mplayer EDL file, version 2
+ < id1 filename1
+ < id2 filename2
+
+ +10 id1 *
+ +10 id2 *
+ +10 id1 *
+ +10 id2 *
+ +10 id1 *
+ +10 id2 *
+
+This plays time 0-10 from filename1, then 0-10 from filename1, then
+10-20 from filename1, then 10-20 from filename2, then 20-30 from
+filename1, then 20-30 from filename2.
+
+::
+
+ mplayer EDL file, version 2
+ < t1 filename1
+ < t2 filename2
+
+ t1 * +2 # segment 1
+ +2 t2 100 # segment 2
+ t1 * # segment 3
+ t2 *-* # segment 4
+ t1 3 -* # segment 5
+ +0.111111 t2 102.5 # segment 6
+ 7.37 t1 5 +1 # segment 7
+
+This rather pathological example illustrates the rules for filling in
+implied data. All the values can be determined by recursively applying
+the rules given above, and the full end result is this::
+
+ +2 0-2 t1 0-2 # segment 1
+ +2 2-4 t2 100-102 # segment 2
+ +0.758889 4-4.758889 t1 2-2.758889 # segment 3
+ +0.5 4.4758889-5.258889 t2 102-102.5 # segment 4
+ +2 5.258889-7.258889 t1 3-5 # segment 5
+ +0.111111 7.258889-7.37 t2 102.5-102.611111 # segment 6
+ +1 7.37-8.37 t1 5-6 # segment 7