#3 divide-by-zero with -ps and ac3 audio

[Mike]

dvbstream fails with /0 when using -ps and AC3 audio.
(for australian HD TV)

mpegtools/transform.c:1563 :
nframes = (p->count-off-3-ac3_off)/
ai.framesize + 1;

ai = {layer = 0, bit_rate = 0, frequency = 0, mode =
3220828495, mode_extension = 65536, emphasis = 0,
framesize = 0, off = 0}