Originally committed as revision 3136 to svn://svn.ffmpeg.org/ffmpeg/trunk
/**
* called at the beginning of each frame to get a buffer for it.
* if pic.reference is set then the frame will be read later by lavc
- * width and height should be rounded up to the next multiple of 16
+ * avcodec_align_dimensions() should be used to find the required width and
+ * height, as they normally need to be rounded up to the next multiple of 16
* - encoding: unused
* - decoding: set by lavc, user can override
*/