ffprobe: add -read_intervals option

This is also useful to test seeking on an input file.

This also addresses trac ticket #1437.

1 files changed, 64 insertions, 0 deletions

diff --git a/doc/ffprobe.texi b/doc/ffprobe.texi
index 20f5f4acc7..777dbe7506 100644
--- a/doc/ffprobe.texi
+++ b/doc/ffprobe.texi
@@ -230,6 +230,70 @@ corresponding stream section.
 Count the number of packets per stream and report it in the
 corresponding stream section.
 
+@item -read_intervals @var{read_intervals}
+
+Read only the specified intervals. @var{read_intervals} must be a
+sequence of interval specifications separated by ",".
+@command{ffprobe} will seek to the interval starting point, and will
+continue reading from that.
+
+Each interval is specified by two optional parts, separated by "%".
+
+The first part specifies the interval start position. It is
+interpreted as an abolute position, or as a relative offset from the
+current position if it is preceded by the "+" character. If this first
+part is not specified, no seeking will be performed when reading this
+interval.
+
+The second part specifies the interval end position. It is interpreted
+as an absolute position, or as a relative offset from the current
+position if it is preceded by the "+" character. If the offset
+specification starts with "#", it is interpreted as the number of
+packets to read (not including the flushing packets) from the interval
+start. If no second part is specified, the program will read until the
+end of the input.
+
+Note that seeking is not accurate, thus the actual interval start
+point may be different from the specified position. Also, when an
+interval duration is specified, the absolute end time will be computed
+by adding the duration to the interval start point found by seeking
+the file, rather than to the specified start value.
+
+The formal syntax is given by:
+@example
+@var{INTERVAL}  ::= [@var{START}|+@var{START_OFFSET}][%[@var{END}|+@var{END_OFFSET}]]
+@var{INTERVALS} ::= @var{INTERVAL}[,@var{INTERVALS}]
+@end example
+
+A few examples follow.
+@itemize
+@item
+Seek to time 10, read packets until 20 seconds after the found seek
+point, then seek to position @code{01:30} (1 minute and thirty
+seconds) and read packets until position @code{01:45}.
+@example
+10%+20,01:30%01:45
+@end example
+
+@item
+Read only 42 packets after seeking to position @code{01:23}:
+@example
+01:23%+#42
+@end example
+
+@item
+Read only the first 20 seconds from the start:
+@example
+%+20
+@end example
+
+@item
+Read from the start until position @code{02:30}:
+@example
+%02:30
+@end example
+@end itemize
+
 @item -show_private_data, -private
 Show private data, that is data depending on the format of the
 particular shown element.