lavf: add audio_preload option, this allows interleaving audio earlier

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/options.c

@@ -116,6 +116,7 @@ static const AVOption options[]={
 {"careful", NULL, 0, AV_OPT_TYPE_CONST, {.dbl = FF_ER_CAREFUL }, INT_MIN, INT_MAX, D, "fer"},
 {"explode", "abort decoding on error recognition", 0, AV_OPT_TYPE_CONST, {.dbl = FF_ER_EXPLODE }, INT_MIN, INT_MAX, D, "fer"},
 {"fpsprobesize", "number of frames used to probe fps", OFFSET(fps_probe_size), AV_OPT_TYPE_INT, {.dbl = -1}, -1, INT_MAX-1, D},
+{"audio_preload", "microseconds by which audio packets should be interleaved earlier", OFFSET(audio_preload), AV_OPT_TYPE_INT, {.dbl = 0}, 0, INT_MAX-1, E},
 {NULL},
 };