From d0d9272580283645f9ac47a55dd471674c1bc9a4 Mon Sep 17 00:00:00 2001 From: Nicolas George Date: Wed, 25 Jul 2012 17:23:39 +0200 Subject: faq: explain about new streams, probesize and analyzeduration. --- doc/faq.texi | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'doc/faq.texi') diff --git a/doc/faq.texi b/doc/faq.texi index d10faa1278..950d2e8330 100644 --- a/doc/faq.texi +++ b/doc/faq.texi @@ -318,6 +318,22 @@ specifying the exact format. aconvert=s16:stereo:packed @end example +@section Why does FFmpeg not see the subtitles in my VOB file? + +VOB and a few other formats do not have a global header that describes +everything present in the file. Instead, applications are supposed to scan +the file to see what it contains. Since VOB files are frequently large, only +the beginning is scanned. If the subtitles happen only later in the file, +they will not be initally detected. + +Some applications, including the @code{ffmpeg} command-line tool, can only +work with streams that were detected during the initial scan; streams that +are detected later are ignored. + +The size of the initial scan is controlled by two options: @code{probesize} +(default ~5 Mo) and @code{analyzeduration} (default 5,000,000 µs = 5 s). For +the subtitle stream to be detected, both values must be large enough. + @chapter Development @section Are there examples illustrating how to use the FFmpeg libraries, particularly libavcodec and libavformat? -- cgit v1.2.3