doc/avconv: expand documentation for some options.

doc/avconv.texi

@@ -82,13 +82,15 @@ described.
 @table @option
 
 @item -f @var{fmt} (@emph{input/output})
-Force format.
+Force input or output file format. The format is normally autodetected for input
+files and guessed from file extension for output files, so this option is not
+needed in most cases.
 
 @item -i @var{filename} (@emph{input})
 input file name
 
 @item -y (@emph{global})
-Overwrite output files.
+Overwrite output files without asking.
 
 @item -c[:@var{stream_specifier}] @var{codec} (@emph{input/output,per-stream})
 @itemx -codec[:@var{stream_specifier}] @var{codec} (@emph{input/output,per-stream})
@@ -111,9 +113,8 @@ will copy all the streams except the second video, which will be encoded with
 libx264, and the 138th audio, which will be encoded with libvorbis.
 
 @item -t @var{duration} (@emph{output})
-Restrict the transcoded/captured video sequence
-to the duration specified in seconds.
-@code{hh:mm:ss[.xxx]} syntax is also supported.
+Stop writing the output after its duration reaches @var{duration}.
+@var{duration} may be a number in seconds, or in @code{hh:mm:ss[.xxx]} form.
 
 @item -fs @var{limit_size} (@emph{output})
 Set the file size limit.
@@ -131,7 +132,7 @@ Set the input time offset in seconds.
 @code{[-]hh:mm:ss[.xxx]} syntax is also supported.
 The offset is added to the timestamps of the input files.
 Specifying a positive offset means that the corresponding
-streams are delayed by 'offset' seconds.
+streams are delayed by @var{offset} seconds.
 
 @item -metadata[:metadata_specifier] @var{key}=@var{value} (@emph{output,per-metadata})
 Set a metadata key/value pair.
@@ -158,9 +159,10 @@ This option is deprecated and has no effect, use -loglevel
 to set verbosity level.
 
 @item -target @var{type} (@emph{output})
-Specify target file type ("vcd", "svcd", "dvd", "dv", "dv50", "pal-vcd",
-"ntsc-svcd", ... ). All the format options (bitrate, codecs,
-buffer sizes) are then set automatically. You can just type:
+Specify target file type (@code{vcd}, @code{svcd}, @code{dvd}, @code{dv},
+@code{dv50}). @var{type} may be prefixed with @code{pal-}, @code{ntsc-} or
+@code{film-} to use the corresponding standard. All the format options
+(bitrate, codecs, buffer sizes) are then set automatically. You can just type:
 
 @example
 avconv -i myfile.avi -target vcd /tmp/vcd.mpg
@@ -650,7 +652,7 @@ it will usually display as 0 if not supported.
 @item -timelimit @var{duration} (@emph{global})
 Exit after avconv has been running for @var{duration} seconds.
 @item -dump (@emph{global})
-Dump each input packet.
+Dump each input packet to stderr.
 @item -hex (@emph{global})
 When dumping packets, also dump the payload.
 @item -ps @var{size}