+
+<p>
+ This chapter provides a short primer on video files, formats and
+ codecs – because it is often cause for confusion:
+</p>
+
+<p>
+ A video file is a <dfn>container</dfn>. It usually contains one
+ <dfn>video track</dfn> and one or more <dfn>audio tracks</dfn>.
+ How these tracks are stored in the file is defined by the
+ <dfn>file format</dfn>. Common formats are
+ avi, mov, ogg, mkv, mpeg, mpeg-ts, mp4, flv, or vob.
+</p>
+<p>
+ Each of the tracks by itself is encoded using a <abbr
+ title="Coder-Decoder"><dfn>Codec</dfn></abbr>. Common video codecs
+ are h264, mpeg2, mpeg4, theora, mjpeg, wmv3. Common audio codecs are
+ mp2, mp3, dts, aac, wav/pcm.
+</p>
+<p>
+ Not all codecs can be packed into a given format. For example the
+ mpeg format is limited to mpeg2, mpeg4 and mp3 codecs (not entirely true).
+ DVDs do have stringent limitations as well. The opposite would be .avi;
+ pretty much every audio/video codec combination can be contained in an avi
+ file-format.
+</p>
+<p>
+ To make things worse, naming conventions for video codecs and formats are
+ often identical (especially MPEG ones) which leads to confusion.
+ All in all it is a very wide and deep field. Suffice there are different
+ uses for different codecs and formats.
+</p>
+
+<h2>Ardour specific issues</h2>
+<p>
+ Ardour supports a wide variety of video file formats codecs. More
+ specifically, Ardour itself actually does not support any video at all
+ but delegates handling of video files to <a
+ href="http://ffmpeg.org/">ffmpeg</a>, which supports over 350 different
+ video codecs and more than 250 file formats.
+</p>
+<p>
+ When importing a video into Ardour, it will be <dfn>transcoded</dfn>
+ (changed from one format and codec to another) to avi/mjpeg for internal
+ use (this allows reliable seeking to frames at low CPU cost — the
+ file size will increase, but hard disks are large and fast).
+</p>
+<p>
+ The export dialog includes presets for common format and codec
+ combinations (such as DVD, web-video,..). If in doubt use one of the
+ presets.
+</p>
+<p>
+ As last note: every time a video is transcoded, the quality can only get
+ worse. Hence for the final mastering/<abbr
+ title="Multiplexing Audio and Video">muxing</abbr> process, one should
+ always to back and use the original source of the video.
+</p>
+